View source for James Webb Space Telescope

{{Short description|NASA/ESA/CSA space telescope launched in 2021}}
{{Use American English|date=March 2018}}
{{Use dmy dates|date=January 2022}}
{{Infobox spaceflight
| name               = James Webb Space Telescope
| names_list         = Next Generation Space Telescope (NGST; 1996–2002)
| image              = JWST spacecraft model 3.png
| image_caption      = Rendering of the fully deployed James Webb Space Telescope
| image_upright      = <!-- Use this parameter to scale the image, instead of the deprecated "image_size"; see WP:IMGSIZE. -->
| mission_type       = [[Space observatory|Astronomy]]
| operator           = [[Space Telescope Science Institute|STScI]] ([[NASA]])<ref name="jwstPartners">{{cite web|url=https://www.jwst.nasa.gov/faq.html#partners|title=NASA JWST "Who are the partners in the Webb project?"|publisher=NASA|access-date=18 November 2011|archive-date=29 November 2011|archive-url=https://web.archive.org/web/20111129213226/http://www.jwst.nasa.gov/faq.html#partners|url-status=live}} {{PD-notice}}</ref> / [[European Space Agency|ESA]] / [[Canadian Space Agency|CSA]]
| website            = {{URL|https://jwst.nasa.gov/}} <br />{{URL|https://webbtelescope.org/}}
| mission_duration   = {{Unbulleted list|{{time interval|25 December 2021 12:20|show=ymd|sep=,}} (elapsed)|{{frac|5|1|2}} years (primary mission)<ref>{{cite web|url=https://jwst.nasa.gov/content/about/faqs/faq.html#howlong|title=FAQ Full General Public Webb Telescope/NASA|website=jwst.nasa.gov|access-date=13 January 2022|archive-date=23 July 2019|archive-url=https://web.archive.org/web/20190723142004/https://jwst.nasa.gov/content/about/faqs/faq.html#howlong|url-status=live}}</ref>|10 years (planned)|20 years (expected life)<ref>{{cite web|url=https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-excess-fuel-likely-to-extend-its-lifetime-expectations/|title=NASA Says Webb's Excess Fuel Likely to Extend its Lifetime Expectations – James Webb Space Telescope|website=blogs.nasa.gov|date=29 December 2021 |access-date=30 December 2021|archive-date=6 January 2022|archive-url=https://web.archive.org/web/20220106191652/https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-excess-fuel-likely-to-extend-its-lifetime-expectations/|url-status=live}}</ref>}}
| manufacturer       = {{Unbulleted list|[[Northrop Grumman]]|[[Ball Aerospace & Technologies]]|[[L3Harris]]<ref name="jwstPartners" />}}
| launch_mass        = {{cvt|6500|kg}}<ref name="James Webb Space Telescope (JWST)">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2021-130A|title=James Webb Space Telescope (JWST)|publisher=[[NASA Space Science Data Coordinated Archive]] |access-date=10 February 2023}}</ref>
| dimensions         = {{cvt|21.197|x|14.162|m}},<ref name="Webb Key Facts">{{cite web|url=https://webb.nasa.gov/content/about/faqs/facts.html|title=Webb Key Facts|date=June 2022 |publisher=Goddard Space Flight Center, NASA|access-date=7 April 2023}}</ref> sunshield
| power              = 2 [[watt|kW]]
| launch_date        = {{Start date|2021|12|25|df=yes}}, 12:20 [[Coordinated Universal Time|UTC]]<ref name="James Webb Space Telescope (JWST)" />
| launch_rocket      = [[Ariane 5|Ariane 5 ECA+]] (S/N 5113, Flight  
[[Ariane flight VA256|VA256]])
| launch_site        = {{Nowrap|[[Guiana Space Centre|Guiana]], [[ELA-3]]}}
| launch_contractor  = [[Arianespace]]
| entered_service    = 12 July 2022
| deactivated        = 
| last_contact       = 
| decay_date         = 
| orbit_reference    = [[Lagrange point|Sun–Earth L<sub>2</sub> orbit]]
| orbit_regime       = [[Halo orbit]]
| orbit_periapsis    = {{cvt|250000|km}}<ref name="orbit">{{cite web |title=JWST Orbit |url=https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-orbit |website=JWST User Documentation |publisher=Space Telescope Science Institute |access-date=25 December 2021 |archive-date=11 July 2022 |archive-url=https://web.archive.org/web/20220711230845/https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-orbit |url-status=live }}</ref>
| orbit_apoapsis     = {{cvt|832000|km}}<ref name="orbit" />
| orbit_inclination  = 
| orbit_period       = 6 months
| apsis              = apsis
| telescope_name     = 
| telescope_type     = [[Korsch telescope]]
| telescope_diameter = {{cvt|6.5|m}}
| telescope_focal_length = {{cvt|131.4|m}}
| telescope_focal_ratio = {{f/|20.2}}
| telescope_area     = {{cvt|25.4|m2}}<ref>{{cite web|title=JWST Telescope|url=https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-telescope|work=James Webb Space Telescope User Documentation|publisher=Space Telescope Science Institute|date=23 December 2019|access-date=11 June 2020|archive-date=11 July 2022|archive-url=https://web.archive.org/web/20220711230845/https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-telescope|url-status=live}} {{PD-notice}}</ref>
| telescope_wavelength = 0.6–28.5 μm ([[orange (colour)|orange]] to mid-[[infrared]])
| instruments_list   = {{Infobox|child=yes
  | headerstyle      = background: #ddf;
  | header1          = Instruments
  | data2            = {{Hlist|[[Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph|FGS-NIRISS]]|[[MIRI (Mid-Infrared Instrument)|MIRI]]|[[NIRCam]]|[[NIRSpec]]}}
  | header3          = Elements
  | data4            = {{plainlist|
* [[Integrated Science Instrument Module]]
* [[Optical Telescope Element]]
* Spacecraft ([[Spacecraft bus (JWST)|Bus]] and [[Sunshield (JWST)|Sunshield]])}}
  }}
| trans_band         = {{ubl
 | [[S band|S-band]], [[telemetry]] and [[telecommand]]
 | [[Ka band|K<sub>a</sub>-band]], science data downlink
 }}
| trans_bandwidth    = {{ubli
 | S-band up: 16&nbsp;kbit/s
 | S-band down: 40&nbsp;kbit/s
 | K<sub>a</sub>-band down: up to 28&nbsp;Mbit/s<ref>{{cite journal |last1=Hecht |first1=Jeff |last2=Potter |first2=Ned |last3=Koziol |first3=Michael |year=2022 |title=Inside the Universe Machine |journal=IEEE Spectrum |volume=59 |issue=9 |page=29|doi=10.1109/MSPEC.2022.9881257 |s2cid=252112744 }}</ref>
 }}
| insignia           = JWST Launch Logo.png
| insignia_caption   = James Webb Space Telescope mission logo
| insignia_upright   = 0.8 <!-- Use this parameter to scale the image, instead of the deprecated "insignia_size"; see WP:IMGSIZE. -->
| programme          = '''[[Large Strategic Science Missions]]'''<br/> ''Astrophysics Division''
| previous_mission   = [[Chandra X-ray Observatory]]
| next_mission       = [[Nancy Grace Roman Space Telescope]]
}}

The '''James Webb Space Telescope''' ('''JWST''') is a [[space telescope]] designed to conduct [[infrared astronomy]]. As the largest telescope in space, it is equipped with high-resolution and high-sensitivity instruments, allowing it to view objects too old, [[List of the most distant astronomical objects|distant]], or faint for the [[Hubble Space Telescope]].<ref name="SA-20221201">{{cite news |last=Moskowitz |first=Clara |date=1 December 2022 |title=How JWST Is Changing Our View of the Universe – The James Webb Space Telescope has sparked a new era in astronomy |work=[[Scientific American]] |url=https://www.scientificamerican.com/article/how-jwst-is-changing-our-view-of-the-universe/ |url-status=live |accessdate=15 November 2022 |archive-url=https://web.archive.org/web/20221115141753/https://www.scientificamerican.com/article/how-jwst-is-changing-our-view-of-the-universe/ |archive-date=15 November 2022}}</ref> This enables investigations across many fields of [[astronomy]] and [[cosmology]], such as observation of the [[Population III star|first stars]] and the [[Galaxy formation and evolution|formation of the first galaxies]], and detailed atmospheric characterization of [[potentially habitable exoplanet]]s.<ref name="NYT-20220823" /><ref name="WP-20220805" /><ref name="SA-20230123">{{cite news |last=O'Callaghan |first=Jonathan |date=23 January 2023 |title=JWST Heralds a New Dawn for Exoplanet Science – The James Webb Space Telescope is opening an exciting new chapter in the study of exoplanets and the search for life beyond Earth |work=[[Scientific American]] |url=https://www.scientificamerican.com/article/jwst-heralds-a-new-dawn-for-exoplanet-science/ |accessdate=25 January 2023}}</ref>

Although the Webb's mirror diameter is 2.7 times larger than that of the Hubble Space Telescope, it produces images of comparable [[optical resolution|resolution]] because it observes in the longer-wavelength infrared spectrum. The longer the wavelength of the spectrum, the larger the information-gathering surface required (mirrors in the infrared spectrum or antenna area in the millimeter and radio ranges) for an image comparable in clarity to the visible spectrum of the Hubble Space Telescope.

The Webb was launched on 25 December 2021 on an Ariane 5 rocket from [[Kourou]], French Guiana. In January 2022 it arrived at its destination, a solar orbit near the Sun–Earth [[Lagrange point#L2 point|L<sub>2</sub> Lagrange point]], about {{convert|1.5|e6km|mi|abbr=out|sp=us}} from Earth. [[Webb's First Deep Field|The telescope's first image]] was released to the public on 11 July 2022.<ref>{{cite web |last1=Fisher |first1=Alise |last2=Pinol |first2=Natasha |last3=Betz |first3=Laura |date=11 July 2022 |title=President Biden Reveals First Image from NASA's Webb Telescope |url=http://www.nasa.gov/press-release/president-biden-reveals-first-image-from-nasa-s-webb-telescope |access-date=2022-07-12 |website=NASA |archive-date=12 July 2022 |archive-url=https://web.archive.org/web/20220712074730/https://www.nasa.gov/press-release/president-biden-reveals-first-image-from-nasa-s-webb-telescope/ |url-status=live }}</ref>

The U.S. [[National Aeronautics and Space Administration]] (NASA) led Webb's design and development and partnered with two main agencies: the [[European Space Agency]] (ESA) and the [[Canadian Space Agency]] (CSA). The NASA [[Goddard Space Flight Center]] in [[Maryland]] managed telescope development, while the [[Space Telescope Science Institute]] in [[Baltimore]] on the [[Homewood Campus of Johns Hopkins University]] operates Webb. The primary contractor for the project was [[Northrop Grumman]].

The [[#Naming concerns|telescope is named]] after [[James E. Webb]], who was the [[List of administrators and deputy administrators of NASA|administrator of NASA]] from 1961 to 1968 during the [[Project Mercury|Mercury]], [[Project Gemini|Gemini]], and [[Apollo program|Apollo]] programs.

Webb's [[primary mirror]] consists of 18 hexagonal [[Segmented mirror|mirror segments]] made of [[gold]]-plated [[beryllium]], which together create a {{convert|6.5|m|ft|adj=mid|-diameter|abbr=out|sp=us}} mirror, compared with Hubble's {{cvt|2.4|m|ftin|adj=on}}. This gives Webb a [[Aperture|light-collecting area]] of about {{Convert|25|m2|abbr=on}}, about six times that of Hubble. Unlike Hubble, which observes in the [[Ultraviolet|near ultraviolet]] and [[visible spectrum|visible]] (0.1 to 0.8&nbsp;[[μm]]), and [[near infrared]] (0.8–2.5&nbsp;μm)<ref name=CWHT/> spectra, Webb observes a lower frequency range, from long-wavelength visible [[light]] (red) through mid-infrared (0.6–28.5&nbsp;μm).<ref>{{Cite web |title=Fact Sheet - NASA Science |url=https://science.nasa.gov/mission/webb/fact-sheet/ |access-date=2024-11-07 |website=science.nasa.gov |date=June 2022 |language=en-US}}</ref> The telescope must be kept extremely cold, below {{cvt|50|K|0}}, so that the [[infrared]] light [[Black-body radiation|emitted]] by the telescope itself does not interfere with the collected light. Its five-layer [[Sunshield (JWST)|sunshield]] protects it from warming by the Sun, Earth, and Moon.

Initial designs for the telescope, then named the Next Generation Space Telescope, began in 1996. Two concept studies were commissioned in 1999, for a potential launch in 2007 and a US$1 billion budget. The program was plagued with enormous cost overruns and delays. A major redesign was accomplished in 2005, with construction completed in 2016, followed by years of exhaustive testing, at a total cost of US$10 billion.

== Features ==
The mass of the James Webb Space Telescope (JWST) is about half that of the [[Hubble Space Telescope]]. Webb has a {{convert|6.5|m|ft|adj=mid|abbr=off|sp=us|-diameter}} [[gold]]-coated [[beryllium]] [[primary mirror]] made up of 18 separate hexagonal mirrors. The mirror has a polished area of {{cvt|26.3|m2|ft2}}, of which {{cvt|0.9|m2|ft2}} is obscured by the secondary support struts,<ref>{{cite journal|arxiv=1203.0002|doi=10.1117/1.OE.51.1.011011 |title=Experience with the Hubble Space Telescope: 20 years of an archetype|year=2012|last1=Lallo|first1=Matthew D.|s2cid=15722152|journal=Optical Engineering|volume=51|issue=1|pages=011011–011011–19 |bibcode=2012OptEn..51a1011L}}</ref> giving a total collecting area of {{cvt|25.4|m2|ft2}}. This is over six times larger than the collecting area of Hubble's {{convert|2.4|m|ft|adj=on|abbr=unit|sp=us}} diameter mirror, which has a collecting area of {{cvt|4.0|m2|ft2}}. The mirror has a gold coating to provide infrared [[reflectivity]] and this is covered by a thin layer of glass for durability.<ref>{{cite web |title=Mirrors Webb/NASA |url=https://webb.nasa.gov/content/observatory/ote/mirrors/index.html |access-date=2022-07-12 |website=webb.nasa.gov |language=en |archive-date=4 February 2022 |archive-url=https://web.archive.org/web/20220204204441/https://webb.nasa.gov/content/observatory/ote/mirrors/index.html |url-status=live }}</ref>

Webb is designed primarily for [[Infrared astronomy|near-infrared astronomy]], but can also see orange and red visible light, as well as the mid-infrared region, depending on the instrument being used.<ref name="NYT-20220823">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |date=23 August 2022 |title=How the Webb Telescope Expanded My Universe – As new images of Jupiter and a galactic survey spring forth from NASA's new observatory, our cosmic affairs correspondent confesses he didn't anticipate their power. |work=[[The New York Times]] |url=https://www.nytimes.com/2022/08/23/science/james-webb-telescope-jupiter-galaxies.html |url-status=live |access-date=24 August 2022 |archive-url=https://web.archive.org/web/20220824005838/https://www.nytimes.com/2022/08/23/science/james-webb-telescope-jupiter-galaxies.html |archive-date=24 August 2022}}</ref><ref name="WP-20220805">{{cite news |last=Achenbach |first=Joel |date=5 August 2022 |title=The Webb telescope is astonishing. But the universe is even more so – This new tool can't do everything, but it's capturing some of the first light emitted after the big bang, and that is already revealing wonders |newspaper=[[The Washington Post]] |url=https://www.washingtonpost.com/outlook/2022/08/05/webb-telescope-universe-big-bang/ |url-status=live |access-date=7 August 2022 |archive-url=https://web.archive.org/web/20220807145228/https://www.washingtonpost.com/outlook/2022/08/05/webb-telescope-universe-big-bang/ |archive-date=7 August 2022}}</ref> It can detect objects up to 100 times fainter than Hubble can, and objects much earlier in the [[Chronology of the universe|history of the universe]], back to [[redshift]] z≈20 (about 180 million years [[cosmic time]] after the [[Big Bang]]).<ref name="deepersky">{{cite web|title=A Deeper Sky &#124; by Brian Koberlein|url=https://briankoberlein.com/blog/deeper-sky|website=briankoberlein.com|access-date=5 January 2022|archive-date=19 March 2022|archive-url=https://web.archive.org/web/20220319062831/https://briankoberlein.com/blog/deeper-sky/|url-status=live}}</ref> For comparison, the [[Population III star|earliest stars]] are thought to have formed between z≈30 and z≈20 (100–180 million years cosmic time),<ref name=FAQ_scientists>{{cite web|url=https://jwst.nasa.gov/content/forScientists/faqScientists.html|title=FAQ for Scientists Webb Telescope/NASA|website=jwst.nasa.gov|access-date=5 January 2022|archive-date=5 January 2022|archive-url=https://web.archive.org/web/20220105200219/https://www.jwst.nasa.gov/content/forScientists/faqScientists.html|url-status=live}}</ref> and the first galaxies may have formed around redshift z≈15 (about 270 million years cosmic time). Hubble is unable to see further back than very early [[reionization]]<ref name="yale20160303">{{cite web |url=http://news.yale.edu/2016/03/03/shattering-cosmic-distance-record-once-again |title=Shattering the cosmic distance record, once again |publisher=[[Yale University]] |first=Jim |last=Shelton |date=3 March 2016 |access-date=4 March 2016 |archive-date=13 March 2016 |archive-url=https://web.archive.org/web/20160313104425/http://news.yale.edu/2016/03/03/shattering-cosmic-distance-record-once-again |url-status=live }}</ref><ref name="heic1604">{{cite web |url=http://www.spacetelescope.org/news/heic1604/ |title=Hubble breaks cosmic distance record |website=SpaceTelescope.org |id=heic1604 |date=3 March 2016 |access-date=3 March 2016 |archive-date=8 March 2016 |archive-url=https://web.archive.org/web/20160308035800/http://www.spacetelescope.org/news/heic1604/ |url-status=live }}</ref> at about z≈11.1 (galaxy [[GN-z11]], 400 million years cosmic time).<ref>{{cite journal |title=A Remarkably Luminous Galaxy at ''z''=11.1 Measured with ''Hubble Space Telescope'' Grism Spectroscopy |journal=[[The Astrophysical Journal]] |first1=P. A. |last1=Oesch |first2=G. |last2=Brammer |first3=P. |last3=van Dokkum |display-authors=etal |volume=819 |issue=2 |at=129 |date=March 2016 |arxiv=1603.00461 |bibcode=2016ApJ...819..129O |doi=10.3847/0004-637X/819/2/129|s2cid=119262750 |doi-access=free }}</ref><ref>{{Cite news|url=https://www.sciencealert.com/even-when-hubble-looks-as-far-back-in-time-as-possible-it-still-can-t-find-the-first-stars|title=Hubble Has Looked Back in Time as Far as It Can And Still Can't Find The First Stars|first=Nancy|last=Atkinson|work=Universe Today|via=ScienceAlert|access-date=9 January 2022|archive-date=9 January 2022|archive-url=https://web.archive.org/web/20220109002616/https://www.sciencealert.com/even-when-hubble-looks-as-far-back-in-time-as-possible-it-still-can-t-find-the-first-stars|url-status=live}}</ref><ref name=deepersky/>

The design emphasizes the near to mid-infrared for several reasons:
* high-redshift (very early and distant) objects have their visible emissions shifted into the infrared, and therefore their light can be observed only via infrared [[astronomy]];{{r|CWHT}}
* infrared light passes more easily through [[cosmic dust#Some "dusty" clouds in the universe|dust clouds]] than visible light;<ref name=CWHT>{{cite web |title=Comparison: Webb vs Hubble Telescope – Webb/NASA |url=https://www.jwst.nasa.gov/content/about/comparisonWebbVsHubble.html |access-date=2022-07-12 |website=www.jwst.nasa.gov |language=en |archive-date=21 January 2022 |archive-url=https://web.archive.org/web/20220121063242/https://www.jwst.nasa.gov/content/about/comparisonWebbVsHubble.html |url-status=live }}</ref>
* colder objects such as [[debris disk]]s and planets emit most strongly in the infrared;
* these infrared bands are difficult to study from the ground or by existing space telescopes such as Hubble.

[[File:Atmospheric electromagnetic opacity.svg|thumb|right|upright=2.4|Rough plot of Earth's [[Atmosphere of Earth#Absorption|atmospheric absorption]] (or opacity) to various wavelengths of electromagnetic radiation, including [[visible light]]]]
Ground-based telescopes must look through [[Earth's atmosphere]], which is opaque in many infrared bands (see figure at right). Even where the atmosphere is transparent, many of the target chemical compounds, such as water, carbon dioxide, and [[methane]], also exist in the Earth's atmosphere, vastly complicating analysis. Existing space telescopes such as Hubble cannot study these bands since their mirrors are insufficiently cool (the Hubble mirror is maintained at about {{cvt|15|C|K F|0|disp=sqbr}}) which means that the telescope itself radiates strongly in the relevant infrared bands.<ref name="ipac.caltech.edu"/>

Webb can also observe objects in the [[Solar System]] at an angle of more than 85° from the Sun and having an apparent [[angular velocity|angular rate of motion]] less than 0.03 arc seconds per second.{{efn|name= tracking |JWST was designed with the requirement to track objects that move as fast as Mars, which has a maximum apparent speed on the sky of 30 [[Minute and second of arc#Symbols and abbreviations|mas]]/s, which is the value given in the technical specification, i.e. the nominal value.<ref name="Fisher 2022-07-14">{{cite web |last=Fisher |first=Alise |date=14 July 2022 |title=Webb Images of Jupiter and More Now Available in Commissioning Data |url=https://blogs.nasa.gov/webb/2022/07/14/webb-images-of-jupiter-and-more-now-available-in-commission |website=James Webb Space Telescope (NASA Blogs) |access-date=8 August 2022 |archive-date=16 January 2023 |archive-url=https://web.archive.org/web/20230116231556/https://blogs.nasa.gov/webb/2022/07/14/webb-images-of-jupiter-and-more-now-available-in-commissioning-data/ |url-status=live }}</ref><br />During commissioning, various asteroids were observed to determine the actual limitation for the speed of objects and it turned out to be 67 mas/s, which is more than twice the nominal value. Tracking at rates of 30–67 mas/s showed accuracies similar to tracking of slower targets. Thus, the telescope is able to observe also [[near-Earth asteroids]] (NEAs), comets closer to perihelion and [[interstellar object]]s.{{r|Rigby 2022-07-12|p=8}}<br />Later, after more experience with [[Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph|FGS]] had been gained, the tracking speed limit was finally set to 75 mas/s for routine observations. Higher rates up to 100 mas/s are also possible on special request, as FGS needs multiple guide stars to this end, which introduces complexity and inefficiency. The first observation with a super-fast rate was the [[Double Asteroid Redirection Test|DART]] impact experiment on 26 September 2022.<ref name="Cesari 2023-02-08">{{cite web |last=Thaddeus |first=Cesari |date=8 February 2023 |title=Breaking the Tracking Speed Limit With Webb |url=https://blogs.nasa.gov/webb/2023/02/08/breaking-the-tracking-speed-limit-with-webb/ |website=James Webb Space Telescope (NASA Blogs) |access-date=11 February 2023}}</ref>}} This includes Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, their [[Natural satellite|satellite]]s, and [[comet]]s, [[asteroid]]s and [[minor planet]]s at or beyond the [[orbit of Mars]]. Webb has the near-IR and mid-IR sensitivity to be able to observe virtually all known [[Kuiper belt|Kuiper Belt Objects]].<ref name=FAQ_scientists/><ref name="FAQ-SolarSystem">{{cite web |title=Technical FAQ Specifically On Solar System Observations |url=https://jwst.nasa.gov/content/forScientists/faqSolarsystem.html |website=James Webb Space Telescope |publisher=NASA |access-date=29 July 2022 |archive-date=12 July 2022 |archive-url=https://web.archive.org/web/20220712050031/https://jwst.nasa.gov/content/forScientists/faqSolarsystem.html |url-status=live }}</ref> In addition, it can observe opportunistic and unplanned targets within 48 hours of a decision to do so, such as [[supernova]]e and [[gamma ray burst]]s.<ref name=FAQ_scientists/>

<gallery align="center" mode="packed" heights="200">
File:James Webb Space Telescope 2009 top.jpg|Three-quarter view of the top
File:James Webb Space Telescope 2009 bottom.jpg|Bottom (Sun-facing side)
</gallery>

=== Location and orbit ===
Webb operates in a [[halo orbit]], circling around a point in space known as the Sun–Earth L<sub>2</sub> [[Lagrange point]], approximately {{cvt|1500000|km}} beyond Earth's orbit around the Sun. Its actual position varies between about {{cvt|250000|and(-)|832000|km|mi}} from L<sub>2</sub> as it orbits, keeping it out of both Earth and Moon's shadow. By way of comparison, Hubble orbits {{cvt|550|km}} above Earth's surface, and the Moon is roughly {{cvt|400000|km}} from Earth. Objects near this Sun–Earth {{L2}} point can orbit the Sun in synchrony with the Earth, allowing the telescope to remain at a roughly constant distance<ref name="stsci.edu">{{cite web |url=http://www.stsci.edu/jwst/overview/design/orbit|archive-url=https://web.archive.org/web/20110614201041/http://www.stsci.edu/jwst/overview/design/orbit|url-status=dead|archive-date=14 June 2011 |title=L2 Orbit|publisher=Space Telescope Science Institute|access-date=28 August 2016}}</ref> with continuous orientation of its sunshield and equipment [[Spacecraft bus (JWST)|bus]] toward the [[Sun]], [[Earth]] and [[Moon]]. Combined with its wide shadow-avoiding orbit, the telescope can simultaneously block incoming heat and light from all three of these bodies and avoid even the smallest changes of temperature from Earth and Moon shadows that would affect the structure, yet still maintain uninterrupted solar power and Earth communications on its sun-facing side. This arrangement keeps the temperature of the spacecraft constant and below the {{cvt|50|K|0}} necessary for faint infrared observations.<ref name=nasasunshield>{{cite web|title=The Sunshield|url=http://www.jwst.nasa.gov/sunshield.html|website=nasa.gov|publisher=NASA|access-date=28 August 2016|archive-date=10 August 2017|archive-url=https://web.archive.org/web/20170810062805/https://www.jwst.nasa.gov/sunshield.html|url-status=live}} {{PD-notice}}</ref><ref>{{cite web|url=http://news.nationalgeographic.com/2015/04/150423-hubble-anniversary-webb-telescope-space|title=Hubble Still Wows At 25, But Wait Till You See What's Next|work=National Geographic|author=Drake, Nadia|author-link=Nadia Drake|date=24 April 2015|access-date=24 April 2015|archive-date=23 June 2019|archive-url=https://web.archive.org/web/20190623140359/https://news.nationalgeographic.com/2015/04/150423-hubble-anniversary-webb-telescope-space/|url-status=dead}}</ref>

=== Sunshield protection ===
{{Main|James Webb Space Telescope sunshield}}
[[File:James Webb telescope sunshield.jpg|thumb|upright=1.4|right|Test unit of the sunshield stacked and expanded at the [[Northrop Grumman]] facility in California, 2014]]

To make observations in the [[Infrared|infrared spectrum]], Webb must be kept under {{cvt|50|K}}; otherwise, infrared radiation from the telescope itself would overwhelm its instruments. Its large sunshield blocks light and heat from the Sun, Earth, and Moon, and its position near the Sun–Earth {{L2|nolink=yes}} keeps all three bodies on the same side of the spacecraft at all times.<ref>{{cite web|url=http://jwst.nasa.gov/orbit.html|title=The James Webb Space Telescope|website=nasa.gov|access-date=28 August 2016|archive-date=30 June 2019|archive-url=https://web.archive.org/web/20190630222205/https://jwst.nasa.gov/orbit.html|url-status=live}} {{PD-notice}}</ref> Its [[halo orbit]] around the [[L2 point|L<sub>2</sub> point]] avoids the shadow of the Earth and Moon, maintaining a constant environment for the sunshield and solar arrays.<ref name="stsci.edu"/> The resulting stable temperature for the structures on the dark side is critical to maintaining precise alignment of the primary mirror segments.<ref name=nasasunshield />

The sunshield consists of five layers, each approximately as thin as a human hair.<ref>{{cite web|url=https://www.jwst.nasa.gov/content/about/innovations/coating.html|title=Sunshield Coatings Webb/NASA|website=jwst.nasa.gov|access-date=3 May 2020|archive-date=29 December 2021|archive-url=https://web.archive.org/web/20211229232353/http://jwst.nasa.gov/content/about/innovations/coating.html|url-status=live}} {{PD-notice}}</ref> Each layer is made of [[Kapton E]] film, coated with aluminum on both sides. The two outermost layers have an additional coating of [[doped silicon]] on the Sun-facing sides, to better reflect the Sun's heat back into space.<ref name=nasasunshield /> Accidental tears of the delicate film structure during deployment testing in 2018 led to further delays to the telescope deployment.<ref name="Clery">{{cite web |url=https://www.science.org/content/article/nasa-announces-more-delays-giant-space-telescope |title=NASA announces more delays for giant space telescope |website=Science |last1=Clery |first1=Daniel |date=27 March 2018 |access-date=5 June 2018 |url-access=limited |archive-date=24 December 2021 |archive-url=https://web.archive.org/web/20211224163932/https://www.science.org/content/article/nasa-announces-more-delays-giant-space-telescope |url-status=live }}</ref>

The sunshield was designed to be folded twelve times so that it would fit within the [[Ariane 5|Ariane&nbsp;5]] rocket's [[payload fairing]], which is {{cvt|4.57|m|ft}} in diameter, and {{cvt|16.19|m|ft}} long. The shield's fully deployed dimensions were planned as {{cvt|14.162|x|21.197|m}}.<ref name="Morring">{{cite magazine |last=Morring |first=Frank Jr. |title=JWST Sunshade Folding, Deployment In Test |magazine=[[Aviation Week & Space Technology]] |date=16 December 2013 |pages=48–49 |issn=0005-2175 |url=https://aviationweek.com/defense-space/space/jwst-sunshade-folding-deployment-test |url-access=subscription |access-date=27 December 2021 |archive-date=19 March 2022 |archive-url=https://web.archive.org/web/20220319060604/https://aviationweek.com/defense-space/space/jwst-sunshade-folding-deployment-test |url-status=live }}</ref>

Keeping within the shadow of the sunshield limits the [[field of regard]] of Webb at any given time. The telescope can see 40 percent of the sky from any one position, but can see all of the sky over a period of six months.<ref name="Readyshield">{{cite web |last=Fisher |first=Alise |date=30 December 2021 |title=Webb Ready for Sunshield Deployment and Cooldown |url=https://blogs.nasa.gov/webb/2021/12/30/webb-ready-for-sunshield-deployment-and-cooldown/ |website=James Webb Space Telescope (NASA Blogs) |access-date=31 December 2021 |archive-date=30 December 2021 |archive-url=https://web.archive.org/web/20211230225404/https://blogs.nasa.gov/webb/2021/12/30/webb-ready-for-sunshield-deployment-and-cooldown/ |url-status=live }}</ref>

=== Optics ===
{{Main|Optical Telescope Element}}
[[File:Engineers Clean JWST Secondary Reflector with Carbon Dioxide Snow.jpg|thumb|upright=1.0|right|Engineers [[Carbon dioxide cleaning|cleaning a test mirror with carbon dioxide snow]], 2015]]
[[File:JWST Full Mirror.jpg|thumb|upright=1.0|right|Main mirror assembly from the front with primary mirrors attached, November 2016]]
[[File:JWST_diffraction_spikes.svg|thumb|right|[[Diffraction spikes]] due to mirror segments and spider color-coded]]

Webb's [[primary mirror]] is a {{cvt|6.5|m}}-diameter gold-coated beryllium reflector with a collecting area of {{cvt|25.4|m2}}. If it had been designed as a single, large mirror, it would have been too large for existing launch vehicles. The mirror is therefore composed of 18 hexagonal segments (a technique pioneered by [[Guido Horn d'Arturo]]), which unfolded after the telescope was launched. Image plane [[Wave-front sensing|wavefront sensing]] through [[Gerchberg–Saxton algorithm|phase retrieval]] is used to position the [[mirror segment]]s in the correct location using precise [[actuator]]s. Subsequent to this initial configuration, they only need occasional updates every few days to retain optimal focus.<ref>{{cite web|url=http://www.stsci.edu/jwst/ote/wavefront-sensing-and-control|archive-url=https://archive.today/20120805213402/http://www.stsci.edu/jwst/ote/wavefront-sensing-and-control|url-status=dead|archive-date=5 August 2012|title=JWST Wavefront Sensing and Control|publisher=Space Telescope Science Institute|access-date=9 June 2011}}</ref> This is unlike terrestrial telescopes, for example the [[W. M. Keck Observatory|Keck telescopes]], which continually adjust their mirror segments using [[active optics]] to overcome the effects of gravitational and wind loading.<ref>{{cite web |title=Keck I and Keck II Telescopes |url=https://www.keckobservatory.org/about/telescopes-instrumentation/ |access-date=2022-07-12 |website=W. M. Keck Observatory |archive-date=1 April 2022 |archive-url=https://web.archive.org/web/20220401093119/https://www.keckobservatory.org/about/telescopes-instrumentation/ |url-status=live }}</ref> The Webb telescope uses 132 small actuation motors to position and adjust the optics.<ref name="wired-20191022">{{cite magazine|last=Mallonee|first=Laura|date=22 October 2019|url=https://www.wired.com/story/nasas-biggest-telescope-ever-prepares-2021-launch/|title=NASA's Biggest Telescope Ever Prepares for a 2021 Launch|magazine=Wired|access-date=4 June 2021|url-access=limited|archive-date=16 May 2022|archive-url=https://web.archive.org/web/20220516142720/https://www.wired.com/story/nasas-biggest-telescope-ever-prepares-2021-launch/|url-status=live}}</ref> The actuators can position the mirror with 10&nbsp;[[nanometer]] accuracy.<ref name="Webb blog 2022-01-13" />

Webb's optical design is a [[three-mirror anastigmat]],<ref>{{cite web|url=http://www.stsci.edu/jwst/ote/mirrors|archive-url=https://archive.today/20120805184514/http://www.stsci.edu/jwst/ote/mirrors|url-status=dead|archive-date=5 August 2012|title=JWST Mirrors|publisher=Space Telescope Science Institute|access-date=9 June 2011}}</ref> which makes use of curved secondary and tertiary mirrors to deliver images that are free from [[optical aberrations]] over a wide field. The secondary mirror is {{cvt|0.74|m|ft}} in diameter. In addition, there is a fine steering mirror which can adjust its position many times per second to provide [[image stabilization]]. Point light sources in images taken by Webb have six [[diffraction spike]]s plus two fainter ones, due to the hexagonal shape of the primary mirror segments.<ref>{{cite web |url=http://bbc.co.uk/news/science-environment-60771210 |title=James Webb: 'Fully focused' telescope beats expectations |first=Jonathan |last=Amos |work=[[BBC News]] |date=16 March 2022 |access-date=2022-07-15 |archive-date=11 July 2022 |archive-url=https://web.archive.org/web/20220711223749/https://www.bbc.co.uk/news/science-environment-60771210 |url-status=live }}</ref>

=== Scientific instruments ===
[[File:JWST Nircam1lwres.jpg|thumb|upright=1.0|right|NIRCam wrapped up in 2013]]
[[File:NIRSpec calibration assembly.jpg|thumb|upright=1.0|right|The Calibration Assembly, one component of the NIRSpec instrument]]
[[File:JWST MIRI.jpg|thumb|upright=1.0|right|MIRI]]

The [[Integrated Science Instrument Module]] (ISIM) is a framework that provides electrical power, computing resources, cooling capability as well as structural stability to the Webb telescope. It is made with bonded graphite-epoxy composite attached to the underside of Webb's telescope structure. The ISIM holds the four science instruments and a guide camera.<ref name=isim/>
* [[NIRCam]] (Near Infrared Camera) is an [[Thermographic camera|infrared imager]] which has spectral coverage ranging from the edge of the visible (0.6&nbsp;μm) through to the [[Infrared#Regions|near infrared]] (5&nbsp;μm).<ref>{{cite web|url=http://www.stsci.edu/jwst/instruments/nircam/|archive-url=https://archive.today/20130403110410/http://www.stsci.edu/jwst/instruments/nircam/|url-status=dead|archive-date=3 April 2013|title=James Webb Space Telescope Near Infrared Camera|publisher=STScI|access-date=24 October 2013}}</ref><ref>{{cite web|url=http://ircamera.as.arizona.edu/nircam/|title=NIRCam for the James Webb Space Telescope|publisher=University of Arizona|access-date=24 October 2013|archive-date=3 November 2021|archive-url=https://web.archive.org/web/20211103203919/http://ircamera.as.arizona.edu/nircam/|url-status=live}}</ref> There are 10 sensors each of 4 megapixels. NIRCam serves as the observatory's wavefront sensor, which is required for wavefront sensing and control activities, used to align and focus the main mirror segments. NIRCam was built by a team led by the [[University of Arizona]], with principal investigator [[Marcia J. Rieke]].<ref name="WhoDoesWhatWeb">{{cite web|url=http://www.stsci.edu/jwst/overview/status.html|archive-url=http://arquivo.pt/wayback/20090715053935/http://www.stsci.edu/jwst/overview/status.html |url-status=dead|archive-date=15 July 2009 |title=JWST Current Status|publisher=STScI|access-date=5 July 2008}}</ref>
* [[NIRSpec]] (Near Infrared Spectrograph) performs [[spectroscopy]] over the same wavelength range. It was built by the [[European Space Agency]] (ESA) at [[ESTEC]] in [[Noordwijk]], Netherlands. The leading development team includes members from [[Airbus Defence and Space]], Ottobrunn and Friedrichshafen, Germany, and the [[Goddard Space Flight Center]]; with Pierre Ferruit ([[École normale supérieure de Lyon]]) as NIRSpec project scientist. The NIRSpec design provides three observing modes: a low-resolution mode using a prism, an R~1000 [[Multi-Object Spectrometer|multi-object]] mode, and an R~2700 integral field unit or long-slit spectroscopy mode. Switching of the modes is done by operating a wavelength preselection mechanism called the Filter Wheel Assembly, and selecting a corresponding dispersive element (prism or grating) using the Grating Wheel Assembly mechanism. Both mechanisms are based on the successful ISOPHOT wheel mechanisms of the [[Infrared Space Observatory]]. The multi-object mode relies on a complex micro-shutter mechanism to allow for simultaneous observations of hundreds of individual objects anywhere in NIRSpec's field of view. There are two sensors, each of 4 megapixels.<ref name="nirspec">{{cite web|url=http://sci.esa.int/jwst/45694-nirspec-the-near-infrared-spectrograph/|title=NIRSpec – the near-infrared spectrograph on JWST|publisher=European Space Agency|date=22 February 2015|access-date=2 February 2017|archive-date=3 April 2019|archive-url=https://web.archive.org/web/20190403162415/http://sci.esa.int/jwst/45694-nirspec-the-near-infrared-spectrograph/|url-status=live}}</ref>
* [[MIRI (Mid-Infrared Instrument)|MIRI]] (Mid-Infrared Instrument) measures the mid-to-long-infrared wavelength range from 5 to 27&nbsp;μm.<ref name=miri/><ref name="nasamiri">{{cite web|url=https://jwst.nasa.gov/miri.html|title=JWST: Mid-Infrared Instrument (MIRI)|publisher=NASA|date=2017|access-date=3 February 2017|archive-date=12 June 2019|archive-url=https://web.archive.org/web/20190612134854/https://jwst.nasa.gov/miri.html|url-status=live}} {{PD-notice}}</ref> It contains both a [[thermal camera|mid-infrared camera]] and an imaging [[spectrometer]].<ref name="howBig">{{cite web |title=JWST |url=https://jwst.nasa.gov/faq.html#howbig |url-status=live |archive-url=https://web.archive.org/web/20150626163752/http://www.jwst.nasa.gov/faq.html#howbig |archive-date=26 June 2015 |access-date=29 June 2015 |publisher=NASA}} {{PD-notice}}</ref> MIRI was developed as a collaboration between NASA and a consortium of European countries, and is led by [[George H. Rieke|George Rieke]] (University of Arizona) and [[Gillian Wright (astronomer)|Gillian Wright]] ([[UK Astronomy Technology Centre]], [[Edinburgh]], Scotland).<ref name="WhoDoesWhatWeb"/> The temperature of the MIRI must not exceed {{cvt|6|K|C F|0}}: a helium gas mechanical cooler sited on the warm side of the environmental shield provides this cooling.<ref name="miricooler">{{cite book|url=http://ircamera.as.arizona.edu/MIRI/miricooler.pdf|last1=Banks|first1=Kimberly|last2=Larson|first2=Melora|last3=Aymergen|first3=Cagatay|last4=Zhang|first4=Burt|title=Modeling, Systems Engineering, and Project Management for Astronomy III |chapter=James Webb Space Telescope Mid-Infrared Instrument cooler systems engineering |journal=<!---->|s2cid=17507846|editor2-first=Martin J.|editor2-last=Cullum|editor1-first=George Z.|editor1-last=Angeli |volume=7017|page=5|quote=Fig. 1. Cooler Architecture Overview|access-date=6 February 2016|bibcode=2008SPIE.7017E..0AB|year=2008|doi=10.1117/12.791925|archive-date=6 October 2021|archive-url=https://web.archive.org/web/20211006144251/http://ircamera.as.arizona.edu/MIRI/miricooler.pdf|url-status=live}}</ref>
* [[Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph|FGS/NIRISS]] (Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph), led by the [[Canadian Space Agency]] (CSA) under project scientist John Hutchings ([[NRC Herzberg Astronomy and Astrophysics Research Centre|Herzberg Astronomy and Astrophysics Research Centre]]), is used to stabilize the line-of-sight of the observatory during science observations. Measurements by the FGS are used both to control the overall orientation of the spacecraft and to drive the fine steering mirror for image stabilization. The CSA also provided a Near Infrared Imager and Slitless Spectrograph (NIRISS) module for astronomical imaging and spectroscopy in the 0.8 to 5&nbsp;μm wavelength range, led by principal investigator René Doyon<ref>{{Cite web |title=JWST is ready for launch and amazing science |url=https://www.planetary.org/planetary-radio/2021-jwst-pre-launch-rene-doyon-heidi-hammel-mike-mcelwain |access-date=2023-08-22 |website=The Planetary Society |language=en}}</ref> at the [[Université de Montréal]].<ref name="WhoDoesWhatWeb"/> Although they are often referred together as a unit, the NIRISS and FGS serve entirely different purposes, with one being a scientific instrument and the other being a part of the observatory's support infrastructure.<ref>{{cite journal|last1=Doyon |first1=René |last2=Hutchings |first2=John B. |last3=Beaulieu |first3=Mathilde |last4=Albert |first4=Loic |last5=Lafrenière |first5=David |last6=Willott |first6=Chris |last7=Touahri |first7=Driss |last8=Rowlands |first8=Neil |last9=Maszkiewicz |first9=Micheal |last10=Fullerton |first10=Alex W. |last11=Volk |first11=Kevin |last12=Martel |first12=André R. |last13=Chayer |first13=Pierre |last14=Sivaramakrishnan |first14=Anand |last15=Abraham |first15=Roberto |last16=Ferrarese |first16=Laura |last17=Jayawardhana |first17=Ray |last18=Johnstone |first18=Doug |last19=Meyer |first19=Michael |last20=Pipher |first20=Judith L. |last21=Sawicki |first21=Marcin |title=The JWST Fine Guidance Sensor (FGS) and Near-Infrared Imager and Slitless Spectrograph (NIRISS) |editor-first1=Mark C |editor-first2=Giovanni G |editor-first3=Howard A |editor-first4=Jacobus M |editor-last1=Clampin |editor-last2=Fazio |editor-last3=MacEwen |editor-last4=Oschmann |journal=Space Telescopes and Instrumentation 2012: Optical |series=Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave |date=22 August 2012 |volume=8442 |pages=84422R |doi=10.1117/12.926578 |bibcode=2012SPIE.8442E..2RD |s2cid=120702854 |url=https://ui.adsabs.harvard.edu/abs/2012SPIE.8442E..2RD/abstract}} "FGS features two modules: an infrared camera dedicated to fine guiding of the observatory and a science camera module, the Near-Infrared Imager and Slitless Spectrograph (NIRISS)"</ref>

NIRCam and MIRI feature starlight-blocking [[coronagraph]]s for observation of faint targets such as [[extrasolar planets]] and [[circumstellar disks]] very close to bright stars.<ref name=nasamiri/>

=== Spacecraft bus ===
{{Main|Spacecraft bus (James Webb Space Telescope)}}
[[File:SpacecraftBus-model.jpg|thumb|upright=1.0|right|Diagram of the [[Spacecraft bus (James Webb Space Telescope)|spacecraft bus]]. The solar panel is in green and the light purple panels are radiators.]]

The [[Spacecraft bus (JWST)|spacecraft bus]] is the primary support component of the JWST, hosting a multitude of computing, communication, electric power, propulsion, and structural parts.<ref name="jwstbus">{{cite web|url=http://jwst.nasa.gov/bus.html|title=The Spacecraft Bus|publisher=NASA James Webb Space Telescope|date=2017|access-date=26 November 2016|archive-date=6 July 2019|archive-url=https://web.archive.org/web/20190706094238/https://jwst.nasa.gov/bus.html|url-status=live}} {{PD-notice}}</ref> Along with the sunshield, it forms the spacecraft element of the [[space telescope]].<ref name="observ">{{cite web|url=http://jwst.nasa.gov/observatory.html|title=The JWST Observatory|publisher=NASA|date=2017|quote=The Observatory is the space-based portion of the James Webb Space Telescope system and is {{sic|comprised|hide=y|of}} three elements: the Integrated Science Instrument Module (ISIM), the Optical Telescope Element (OTE), which includes the mirrors and backplane, and the Spacecraft Element, which includes the spacecraft bus and the sunshield|access-date=28 December 2016|archive-date=20 May 2019|archive-url=https://web.archive.org/web/20190520132413/https://jwst.nasa.gov/observatory.html|url-status=live}} {{PD-notice}}</ref><ref name=isimnasa>{{cite web |url=http://jwst.nasa.gov/isim.html|title=Integrated Science Instrument Module (ISIM)|publisher=NASA James Webb Space Telescope|date=2017|access-date=30 November 2016|archive-date=3 December 2016|archive-url=https://web.archive.org/web/20161203070235/http://jwst.nasa.gov/isim.html|url-status=dead}} {{PD-notice}}</ref> The spacecraft bus is on the Sun-facing "warm" side of the sunshield and operates at a temperature of about {{cvt|300|K|C F}}.<ref name=observ/>

The structure of the spacecraft bus has a mass of {{cvt|350|kg}}, and must support the {{cvt|6200|kg}} space telescope. It is made primarily of graphite composite material.<ref name= Willoughby >{{cite magazine |last=Willoughby |first=Scott P. |date=February 2012 |title=PRIME: The Untold Story Of NASA's James Webb Space Telescope |magazine=SatMagazine |publisher=Satnews |url=http://www.satmagazine.com/story.php?number=443229204 |access-date=2021-04-06 |archive-date=11 August 2022 |archive-url=https://web.archive.org/web/20220811145145/http://www.satmagazine.com/story.php?number=443229204 |url-status=live }}</ref> The assembly was completed in California in 2015. It was integrated with the rest of the space telescope leading to its 2021 launch. The spacecraft bus can rotate the telescope with a pointing precision of one [[Minute and second of arc|arcsecond]], and isolates vibration to two milliarcseconds.<ref>{{cite web|url=http://www.compositesworld.com/news/james-webb-space-telescope-spacecraft-inches-towards-full-assembly|title=James Webb Space Telescope spacecraft inches towards full assembly|publisher=Composites World|author=Sloan, Jeff|date=12 October 2015|access-date=28 December 2016|archive-date=24 October 2019|archive-url=https://web.archive.org/web/20191024213903/https://www.compositesworld.com/news/james-webb-space-telescope-spacecraft-inches-towards-full-assembly|url-status=dead}}</ref>

Webb has two pairs of rocket engines (one pair for redundancy) to make course corrections on the way to L<sub>2</sub> and for [[Orbital station-keeping|station keeping]]{{snd}}maintaining the correct position in the halo orbit. Eight smaller thrusters are used for [[Spacecraft attitude control|attitude control]]{{snd}}the correct pointing of the spacecraft.<ref>{{cite web |title=JWST Propulsion |url=https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-spacecraft-bus/jwst-propulsion |website=JWST User Documentation |publisher=Space Telescope Science Institute |access-date=29 December 2021 |archive-date=11 July 2022 |archive-url=https://web.archive.org/web/20220711230847/https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-spacecraft-bus/jwst-propulsion |url-status=live }}</ref> The engines use [[hydrazine]] fuel ({{convert|159|L|USgal|disp=or|sp=us}} at launch) and [[dinitrogen tetroxide]] as oxidizer ({{convert|79.5|L|USgal|disp=or|sp=us}} at launch).<ref>{{cite web|last=Clark|first=Stephen|date=28 November 2021|title=NASA gives green light to fuel James Webb Space Telescope|url=https://spaceflightnow.com/2021/11/28/nasa-gives-green-light-to-fuel-james-webb-space-telescope/|publisher=Spaceflight Now|access-date=2 December 2021|archive-date=25 June 2022|archive-url=https://web.archive.org/web/20220625024136/https://spaceflightnow.com/2021/11/28/nasa-gives-green-light-to-fuel-james-webb-space-telescope/|url-status=live}}</ref>

=== Servicing ===
Webb is not intended to be serviced in space. A crewed mission to repair or upgrade the observatory, as was done for Hubble, would not be possible,<ref>{{cite web |title=Why is Webb not serviceable like Hubble? |url=https://webb.nasa.gov/content/about/faqs/faq.html#serviceable |website=James Webb Space Telescope (FAQ) |access-date=31 December 2021 |archive-date=3 July 2022 |archive-url=https://web.archive.org/web/20220703052705/https://webb.nasa.gov/content/about/faqs/faq.html#serviceable |url-status=live }}</ref> and according to NASA Associate Administrator [[Thomas Zurbuchen]], despite best efforts, an uncrewed remote mission was found to be beyond available technology at the time Webb was designed.<ref name="refuel-natgeog">{{cite web|url=https://www.nationalgeographic.com/science/article/relief-as-nasas-most-powerful-space-telescope-finishes-risky-unfolding|title=Relief as NASA's most powerful space telescope finishes risky unfolding|date=8 January 2022|website=Science|access-date=11 January 2022|archive-date=31 January 2022|archive-url=https://web.archive.org/web/20220131025500/https://www.nationalgeographic.com/science/article/relief-as-nasas-most-powerful-space-telescope-finishes-risky-unfolding|url-status=dead}}</ref> During the long Webb testing period, NASA officials referred to the idea of a servicing mission, but no plans were announced.<ref>{{cite web |last1=Smith |first1=Marcia |title=Zurbuchen Taking One Last Look at JWST Servicing {{as written|Compat|iblity [sic]}} |url=https://spacepolicyonline.com/news/zurbuchen-taking-one-last-look-at-jwst-servicing/ |website=SpacePolicyOnline |access-date=31 December 2021 |date=30 August 2018 |archive-date=31 December 2021 |archive-url=https://web.archive.org/web/20211231061210/https://spacepolicyonline.com/news/zurbuchen-taking-one-last-look-at-jwst-servicing/ |url-status=live }}</ref><ref>{{cite web |last1=Foust |first1=Jeff |title=Scientists, engineers push for servicing and assembly of future space observatories |url=https://spacenews.com/scientists-engineers-push-for-servicing-and-assembly-of-future-space-observatories/ |website=SpaceNews |access-date=31 December 2021 |date=2 February 2018 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144456/https://spacenews.com/scientists-engineers-push-for-servicing-and-assembly-of-future-space-observatories/ |url-status=live }}</ref> Since the successful launch, NASA has stated that nevertheless limited accommodation was made to facilitate future servicing missions. These accommodations included precise guidance markers in the form of crosses on the surface of Webb, for use by remote servicing missions, as well as refillable fuel tanks, removable heat protectors, and accessible attachment points.<ref name="refuel-verge">{{cite web|url=https://www.theverge.com/2021/12/28/22816310/nasa-james-webb-space-telescope-jwst-deployment-sequence|title=NASA's James Webb Space Telescope is about to transform into its final form|first=Loren|last=Grush|date=28 December 2021|website=The Verge|access-date=11 January 2022|archive-date=9 July 2022|archive-url=https://web.archive.org/web/20220709002158/https://www.theverge.com/2021/12/28/22816310/nasa-james-webb-space-telescope-jwst-deployment-sequence|url-status=live}}</ref><ref name="refuel-natgeog"/>

=== Software ===
Webb uses a modified version of [[JavaScript]], called Nombas ScriptEase 5.00e, for its operations; it follows the [[ECMAScript]] standard and "allows for a modular design flow, where on-board scripts call lower-level scripts that are defined as functions". Furthermore, "The script interpreter is run by the flight software, which is written in [[C++]]. The flight software operates the spacecraft and the science instruments."<ref>{{cite journal |last1=Dashevsky |first1=Ilana |last2=Balzano |first2=Vicki |title=JWST: Maximizing. Efficiency and Minimizing Ground Systems |journal=International Symposium on Reducing the Costs of Spacecraft Ground Systems and Operations Proceedings |date=2007 |url=https://www.stsci.edu/~idash/pub/dashevsky0607rcsgso.pdf |access-date=4 December 2022 |archive-date=4 December 2022 |archive-url=https://web.archive.org/web/20221204151902/https://www.stsci.edu/~idash/pub/dashevsky0607rcsgso.pdf |url-status=live }}</ref>

== Comparison with other telescopes ==
[[File:JWST-HST-primary-mirrors.svg|thumb|upright=1.0|right|Comparison with the [[Hubble Space Telescope]] primary mirror]]
[[File:Primary Mirror Size Comparison Between Webb and Hubble.webm|thumb|upright=1.0|right|Primary mirror size comparison between Webb and Hubble]]

The desire for a large infrared space telescope traces back decades. In the United States, the Space Infrared Telescope Facility (later called the [[Spitzer Space Telescope]]) was planned while the Space Shuttle was in development, and the potential for infrared astronomy was acknowledged at that time.<ref name="proceedings.spiedigitallibrary.org">{{cite conference |last1=McCarthy |first1=S. G. |last2=Autio |first2=G. W. |year=1978 |title=Infrared Detector Performance In The Shuttle Infrared Telescope Facility (SIRTF) |url=http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1227080 |conference=1978 Los Angeles Technical Symposium |series=Utilization of Infrared Detectors |publisher=Society of Photographic Instrumentation Engineers |volume=81 |issue=6 June |pages=81–88 |bibcode=1978SPIE..132...81M |doi=10.1117/12.956060 |archive-url=https://web.archive.org/web/20170305015734/http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1227080 |archive-date=5 March 2017 |access-date=8 December 2016 |url-status=live |quote=The tenuous atmosphere above the 400 km nominal flight altitude has no measurable absorption so that detectors operating at all wavelengths from 5 μm to 1000 μm can achieve high radiometric sensitivity.|url-access=subscription }}</ref> Unlike ground telescopes, space observatories are free from atmospheric absorption of infrared light. Space observatories opened a "new sky" for astronomers.

However, there is a challenge involved in the design of infrared telescopes: they need to stay extremely cold, and the longer the wavelength of infrared, the colder they need to be. If not, the background heat of the device itself overwhelms the detectors, making it effectively blind. This can be overcome by careful design. One method is to put the key instruments in a [[Cryogenic storage dewar|dewar]] with an extremely cold substance, such as [[liquid helium]]. The coolant will slowly vaporize, limiting the lifetime of the instrument from as short as a few months to a few years at most.<ref name="ipac.caltech.edu">{{cite web |url=http://www.ipac.caltech.edu/outreach/Edu/orbit.html|title=Infrared astronomy from earth orbit|publisher=Infrared Processing and Analysis Center, NASA Spitzer Science Center, California Institute of Technology|date=2017|url-status=dead|archive-url=https://web.archive.org/web/20161221020839/http://www.ipac.caltech.edu/outreach/Edu/orbit.html|archive-date=21 December 2016}} {{PD-notice}}</ref>

It is also possible to maintain a low temperature by designing the spacecraft to enable near-infrared observations without a supply of coolant, as with the extended missions of the Spitzer Space Telescope and the [[Wide-field Infrared Survey Explorer]], which operated at reduced capacity after coolant depletion. Another example is Hubble's [[Near Infrared Camera and Multi-Object Spectrometer]] (NICMOS) instrument, which started out using a block of [[Solid nitrogen|nitrogen ice]] that depleted after a couple of years, but was then replaced during the [[STS-109]] servicing mission with a [[cryocooler]] that worked continuously. The Webb Space Telescope is designed to cool itself without a dewar, using a combination of sunshields and radiators, with the mid-infrared instrument using an additional cryocooler.<ref>{{cite web|url=https://phys.org/news/2016-06-cold-cooler-nasa-telescope.html|title=How cold can you go? Cooler tested for NASA telescope|publisher=Phys.org|date=14 June 2016|access-date=31 January 2017|archive-date=11 July 2022|archive-url=https://web.archive.org/web/20220711122922/https://phys.org/news/2016-06-cold-cooler-nasa-telescope.html|url-status=live}}</ref>

{| class=wikitable style="margin:10px; text-align:center;"
|-
|+ Selected space telescopes and instruments<ref>{{cite web|url=http://herschel.jpl.nasa.gov/relatedMissions.shtml|title=JPL: Herschel Space Observatory: Related Missions|publisher=NASA, Jet Propulsion Laboratory, Goddard Flight Center, California Institute of Technology|access-date=4 June 2012|archive-date=3 December 2016|archive-url=https://web.archive.org/web/20161203091854/https://herschel.jpl.nasa.gov/relatedMissions.shtml|url-status=live}} {{PD-notice}}</ref>
|-
! Name
! Launch year !! [[Electromagnetic spectrum|Wavelength]] <br />(μm) !! Aperture <br />(m)
! Cooling
|-
| [[Spacelab Infrared Telescope]] (IRT)
| 1985 || 1.7–118 || 0.15
| Helium
|-
| [[Infrared Space Observatory]] (ISO)<ref>{{cite web|url=https://www.cosmos.esa.int/web/iso/what-is-iso-|title=What is ISO?|publisher=[[ESA]]|date=2016|access-date=4 June 2021|archive-date=10 November 2021|archive-url=https://web.archive.org/web/20211110190424/https://www.cosmos.esa.int/web/iso/what-is-iso-|url-status=live}}</ref>
| 1995 || 2.5–240 || 0.60
| Helium
|-
| style="max-width:250px;" | Hubble [[Space Telescope Imaging Spectrograph]] (STIS)
| 1997 || 0.115–1.03 || 2.4
| Passive
|-
| style="max-width:250px;" | Hubble [[Near Infrared Camera and Multi-Object Spectrometer]] (NICMOS)
| 1997 || 0.8–2.4 || 2.4
| Nitrogen, later [[cryocooler]]
|-
| [[Spitzer Space Telescope]]
| 2003 || 3–180 || 0.85
| Helium
|-
| Hubble [[Wide Field Camera 3]] (WFC3)
| 2009 || 0.2–1.7 || 2.4
| Passive and thermo-electric<ref>{{cite web|url=https://www.nasa.gov/content/hubble-space-telescope-wide-field-camera-3|title=Hubble Space Telescope – Wide Field Camera 3|publisher=NASA|date=22 August 2016|access-date=9 December 2016|archive-date=13 November 2021|archive-url=https://web.archive.org/web/20211113213252/https://www.nasa.gov/content/hubble-space-telescope-wide-field-camera-3/|url-status=live}} {{PD-notice}}</ref>
|-
| [[Herschel Space Observatory]]
| 2009 || 55–672 || 3.5
| Helium
|-
| James Webb Space Telescope
| 2021 || 0.6–28.5 || 6.5
| Passive and [[cryocooler]] (MIRI)
|}

Webb's delays and cost increases have been compared to those of its predecessor, the [[Hubble Space Telescope]]. When Hubble formally started in 1972, it had an estimated development cost of US$300 million ({{Inflation|US|300000000|1972|fmt=eq|r=-3}}), but by the time it was sent into orbit in 1990, the cost was about four times that. In addition, new instruments and servicing missions increased the cost to at least US$9 billion by 2006<ref name="nature06"/> ({{Inflation|US|9000000000|2006|fmt=eq|r=-3}}).

== Development history ==
{{For timeline}}

=== Background (development to 2003) ===
{| class=wikitable style="float:right; margin-left:0.5em; font-size:88%; width:30em"
|+ Major milestones
! Year !! Milestone
|-
| 1996 || Next Generation Space Telescope project first proposed (mirror size: 8 m)
|-
| 2001 || NEXUS Space Telescope, a precursor to the Next Generation Space Telescope, cancelled<ref>{{cite web|url=http://strategic.mit.edu/downloads.php|title=Nexus Space Telescope|publisher=MIT|access-date=23 August 2011|archive-date=29 August 2011|archive-url=https://web.archive.org/web/20110829234559/http://strategic.mit.edu/downloads.php|url-status=live}}</ref>
|-
| 2002 || Proposed project renamed James Webb Space Telescope, (mirror size reduced to 6 m)
|-
| 2003 || [[Northrop Grumman]] awarded contract to build telescope
|-
| 2007 || [[Memorandum of Understanding]] signed between NASA and ESA<ref name="2007mou">{{Cite web |last1=Brown |first1=Dwayne |last2=Braukus |first2=Michael |title=NASA – NASA and ESA Sign Agreements for Future Cooperation |url=https://www.nasa.gov/home/hqnews/2007/jun/HQ_07139_Paris_MOUs.html |access-date=2023-08-02 |website=www.nasa.gov |language=en-us |archive-date=19 March 2022 |archive-url=https://web.archive.org/web/20220319194241/https://www.nasa.gov/home/hqnews/2007/jun/HQ_07139_Paris_MOUs.html |url-status=dead }}</ref>
|-
| 2010 || Mission Critical Design Review (MCDR) passed
|-
| 2011 || Proposed cancellation
|-
| 2016 || Final assembly completed
|-
| 25 Dec 2021 || Launch
|}

Discussions of a Hubble follow-on started in the 1980s, but serious planning began in the early 1990s.<ref name="Space_is_changing">{{cite news |author=Gur |first=Haviv Rettig |date=5 January 2022 |title=Space is changing. Webb is just the start, says ex-Israeli who was in from its dawn |work=The Times of Israel |url=https://www.timesofisrael.com/space-is-changing-webb-is-just-the-start-says-ex-israeli-who-was-in-from-its-dawn/ |url-status=live |access-date=7 January 2022 |archive-url=https://web.archive.org/web/20220319060604/https://www.timesofisrael.com/space-is-changing-webb-is-just-the-start-says-ex-israeli-who-was-in-from-its-dawn/ |archive-date=19 March 2022}}</ref> The ''Hi-Z'' telescope concept was developed between 1989 and 1994:<ref>{{cite web|url=http://optics.nasa.gov/concept/hi-z.html|publisher=NASA Space Optics Manufacturing Technology Center|title=Advanced Concepts Studies – The 4 m Aperture "Hi-Z" Telescope|url-status=dead|archive-url=https://web.archive.org/web/20111015142938/http://optics.nasa.gov/concept/hi-z.html|archive-date=15 October 2011}} {{PD-notice}}</ref> a fully baffled{{efn|"Baffled", in this context, means enclosed in a tube in a similar manner to a conventional [[optical telescope]], which helps to stop stray light entering the telescope from the side. For an actual example, see the following link: {{cite conference|author=Freniere, E.R.|conference=Radiation Scattering in Optical Systems|book-title=Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, First-order design of optical baffles|volume=257|pages=19–28|date=1981|bibcode=1981SPIE..257...19F|title=First-order design of optical baffles |doi=10.1117/12.959598}}}} {{cvt|4|m}} aperture infrared telescope that would recede to an orbit at 3 [[Astronomical unit]] (AU).<ref name="stsci1994">{{cite web |url=http://www.stsci.edu/jwst/overview/history/1994|archive-url=https://web.archive.org/web/20110610120136/http://www.stsci.edu/jwst/overview/history/1994|url-status=dead|archive-date=10 June 2011 |title=STSCI JWST History 1994|access-date=29 December 2018}}</ref> This distant orbit would have benefited from reduced light noise from [[Zodiacal cloud|zodiacal dust]].<ref name="stsci1994"/> Other early plans called for a NEXUS precursor telescope mission.<ref name=AANM>{{cite web |url=http://www.nap.edu/html/aanm/web/tier3text/ngst.htm |title=Astrononmy and Astrophysics in the New Millennium |publisher=NASA |access-date=27 July 2011 |archive-date=25 December 2021 |archive-url=https://web.archive.org/web/20211225151946/https://www.nap.edu/html/aanm/web/tier3text/ngst.htm |url-status=live }} {{PD-notice}}</ref><ref name=HIST-NEXUS>{{cite book|chapter-url=http://strategic.mit.edu/docs/3_13_SPIE-4849-39.pdf|first1=Olivier L.|last1=de Weck|first2=David W.|last2=Miller|first3=Gary E.|last3=Mosier|title=Highly Innovative Space Telescope Concepts|volume=4849|page=294|s2cid=18725988|editor1-first=Howard A.|editor1-last=MacEwen|date=2002|chapter=Multidisciplinary analysis of the NEXUS precursor space telescope|doi=10.1117/12.460079|citeseerx=10.1.1.664.8727|bibcode=2002SPIE.4849..294D|access-date=27 July 2011|archive-date=23 September 2017|archive-url=https://web.archive.org/web/20170923001351/http://strategic.mit.edu/docs/3_13_SPIE-4849-39.pdf|url-status=live}}</ref>

Correcting the [[Hubble Space Telescope#Flawed mirror|flawed optics]] of the Hubble Space Telescope (HST) in its first years played a significant role in the birth of Webb.<ref>{{cite web |url= https://science.nasa.gov/mission/hubble/observatory/design/optics/hubbles-mirror-flaw/|title= Hubble's Mirror Flaw|author= |date= 25 November 2019|publisher= NASA|accessdate=19 June 2024}}</ref> In 1993, NASA conducted [[STS-61]], [[Hubble Space Telescope Servicing Mission 1|the Space Shuttle mission]] that replaced HST's camera and installed a retrofit for its imaging spectrograph to compensate for the [[spherical aberration]] in its [[primary mirror]].

The HST & Beyond Committee was formed in 1994 "to study possible missions and programs for optical-ultraviolet astronomy in space for the first decades of the 21st century".<ref>{{cite book |last1=Brown |first1=R. A. |chapter=HST &Beyond Study |title=Science with the Hubble Space Telescope - II. Proceedings of a workshop held in Paris, France, December 4-8, 1995 |editor=Piero Benvenuti |editor2=F.D. Macchetto |editor3=Ethan J. Schreier |location=Baltimore, MD |publisher=Space Telescope Science Institute |year=1996 |chapter-url=https://adsabs.harvard.edu/full/1996swhs.conf..603B  |page=603 |bibcode=1996swhs.conf..603B}}</ref> Emboldened by HST's success, its 1996 report explored the concept of a larger and much colder, infrared-sensitive telescope that could reach back in cosmic time to the birth of the first galaxies. This high-priority science goal was beyond the HST's capability because, as a warm telescope, it is blinded by infrared emission from its own optical system. In addition to recommendations to extend the HST mission to 2005 and to develop technologies for finding planets around other stars, NASA embraced the chief recommendation of HST & Beyond<ref name="Dressler-1996">{{cite web|url=https://www.stsci.edu/files/live/sites/www/files/home/hst/documentation/_documents/HSTandBeyond.pdf|title=Exploration and the Search for Origins: A Vision for Ultraviolet-Optical-Infrared Space Astronomy Report of the 'HST & Beyond' Committee|year=1996|editor-first=A.|editor-last=Dressler|publisher=Association of Universities for Research in Astronomy|website=Stsci.edu|access-date=12 February 2022|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144434/https://www.stsci.edu/files/live/sites/www/files/home/hst/documentation/_documents/HSTandBeyond.pdf|url-status=live}}</ref> for a large, cold space telescope (radiatively cooled far below 0&nbsp;°C), and began the planning process for the future Webb telescope.

Preparation for the 2000 [[Astronomy and Astrophysics Decadal Survey]] (a literature review produced by the [[United States National Research Council]] that includes identifying research priorities and making recommendations for the upcoming decade) included further development of the scientific program for what became known as the Next Generation Space Telescope,<ref name="Stockman-1997">Stockman, H. S. (June 1997). "The Next Generation Space Telescope. Visiting a time when galaxies were young". Space Telescope Science Institute, Baltimore, Maryland. The Association of Universities for Research in Astronomy, Washington, D.C.</ref> and advancements in relevant technologies by NASA. As it matured, studying the birth of galaxies in the young [[universe]], and searching for planets around other stars{{snd}}the prime goals coalesced as "Origins" by HST & Beyond became prominent.{{citation needed|date=February 2025}}

As hoped, the NGST received the highest ranking in the 2000 Decadal Survey.<ref name="Decadal-2000">{{cite book|author=((Astronomy and Astrophysics Survey Committee))|url=https://www.nap.edu/catalog/9839|title=Astronomy and Astrophysics in the New Millennium|author2=((Board on Physics and Astronomy))|author3=((Space Studies Board))|author4=((Commission on Physical Sciences, Mathematics, and Applications))|author5=((National Research Council))|date=16 January 2001|publisher=National Academies Press|isbn=978-0-309-07031-7|location=Washington, D.C.|doi=10.17226/9839|bibcode=2001aanm.book.....N |access-date=15 December 2021|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144439/https://nap.nationalacademies.org/catalog/9839/astronomy-and-astrophysics-in-the-new-millennium|url-status=live}}</ref>

An [[administrator of NASA]], [[Daniel Goldin|Dan Goldin]], coined the phrase "[[faster, better, cheaper]]", and opted for the next big paradigm shift for astronomy, namely, breaking the barrier of a single mirror. That meant going from "eliminate moving parts" to "learn to live with moving parts" (i.e. segmented optics). With the goal to reduce mass density tenfold, [[silicon carbide]] with a very thin layer of glass on top was first looked at, but [[beryllium]] was selected at the end.<ref name="Space_is_changing"/>

The mid-1990s era of "faster, better, cheaper" produced the NGST concept, with an {{cvt|8|m|adj=on}} aperture to be flown to {{L2}}, roughly estimated to cost US$500 million.<ref name="stsci1996">{{cite web|url=http://www.stsci.edu/jwst/overview/history/1996|archive-url=https://web.archive.org/web/20110610120124/http://www.stsci.edu/jwst/overview/history/1996|url-status=dead|archive-date=10 June 2011|title=STSCI JWST History 1996|publisher=Stsci.edu|access-date=16 January 2012}}</ref> In 1997, NASA worked with the Goddard Space Flight Center,<ref>{{Cite web |last=information@eso.org |title=Goddard Space Flight Center design |url=https://www.spacetelescope.org/images/opo9820b/ |access-date=2023-08-02 |website=www.spacetelescope.org |language=en}}</ref> [[Ball Aerospace & Technologies]],<ref>[http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=29549 "ESA Science & Technology: Ball Aerospace design for JWST"]. {{Webarchive|url=https://archive.today/20121212222215/http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=29549 |date=12 December 2012 }}. Sci.esa.int. Retrieved 21 August 2013</ref> and [[TRW Inc.|TRW]]<ref>[http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=29551 "ESA Science & Technology: TRW design for JWST"]. {{Webarchive|url=https://archive.today/20121212002141/http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=29551 |date=12 December 2012 }}. Sci.esa.int. Retrieved 21 August 2013</ref> to conduct technical requirement and cost studies of the three different concepts, and in 1999 selected [[Lockheed Martin]]<ref>[http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=29550 "ESA Science & Technology: Lockheed-Martin design for JWST"]. {{Webarchive|url=https://archive.today/20121213002044/http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=29550 |date=13 December 2012 }}. Sci.esa.int. Retrieved 21 August 2013</ref> and TRW for preliminary concept studies.<ref name="webbpast">{{cite web|url=http://jwstsite.stsci.edu/webb_telescope/webb_past_and_future/|title=HubbleSite – Webb: Past and Future|access-date=13 January 2012|archive-url=https://archive.today/20121210103643/http://jwstsite.stsci.edu/webb_telescope/webb_past_and_future/|archive-date=10 December 2012|url-status=dead}}</ref> Launch was at that time planned for 2007, but the launch date was pushed back many times (see table [[#Time, budget|further down]]).

In 2002, the project was renamed after NASA's second administrator (1961–1968), [[James E. Webb]] (1906–1992).<ref name="nameannounce">{{cite web|url=https://www.nasa.gov/home/hqnews/2002/02-171.txt|title=NASA ANNOUNCES CONTRACT FOR NEXT-GENERATION SPACE TELESCOPE NAMED AFTER SPACE PIONEER|date=10 September 2002|access-date=26 August 2022|publisher=NASA|archive-date=27 August 2022|archive-url=https://web.archive.org/web/20220827013307/https://www.nasa.gov/home/hqnews/2002/02-171.txt|url-status=live}}</ref> Webb led the agency during the [[Apollo program]] and established scientific research as a core NASA activity.<ref name=":4">{{cite web|url=http://www.jwst.nasa.gov/whois.html|title=About James Webb|publisher=NASA|access-date=15 March 2013|archive-date=27 March 2018|archive-url=https://web.archive.org/web/20180327233836/https://www.jwst.nasa.gov/whois.html|url-status=live}} {{PD-notice}}</ref>

In 2003, NASA awarded TRW the US$824.8 million prime contract for Webb. The design called for a de-scoped {{cvt|6.1|m}} primary mirror and a launch date of 2010.<ref>{{cite web|url=http://www.stsci.edu/jwst/news/2003/nasa-announces-contract|archive-url=https://archive.today/20120805155712/http://www.stsci.edu/jwst/news/2003/nasa-announces-contract|url-status=dead|archive-date=5 August 2012|title=TRW Selected as JWST Prime Contractor|date=11 September 2003|access-date=13 January 2012|publisher=STCI}}</ref> Later that year, TRW was acquired by [[Northrop Grumman]] in a hostile bid and became Northrop Grumman Space Technology.<ref name="webbpast"/>

=== Early development and replanning (2003–2007) ===
[[File:JWST people.jpg|thumb|upright=1.8|right|Early full-scale model on display at NASA [[Goddard Space Flight Center]] (2005)]]Development was managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland, with [[John C. Mather]] as its project scientist. The primary contractor was Northrop Grumman Aerospace Systems, responsible for developing and building the spacecraft element, which included the [[satellite bus]], sunshield, Deployable Tower Assembly (DTA) which connects the [[Optical Telescope Element]] to the spacecraft bus, and the Mid Boom Assembly (MBA) which helps to deploy the large sunshields on orbit,<ref>{{cite news| url=http://www.spacedaily.com/reports/Northrop_Grumman_Completes_Fabrication_Of_Sunshield_Deployment_Flight_Structure_For_JWST_999.html| title=Northrop Grumman Completes Fabrication Of Sunshield Deployment Flight Structure For JWST| publisher=Space Daily| date=13 December 2011| access-date=10 December 2014| archive-date=18 January 2022| archive-url=https://web.archive.org/web/20220118030148/https://www.spacedaily.com/reports/Northrop_Grumman_Completes_Fabrication_Of_Sunshield_Deployment_Flight_Structure_For_JWST_999.html| url-status=live}}</ref> while [[Ball Aerospace & Technologies]] was subcontracted to develop and build the OTE itself, and the [[Integrated Science Instrument Module]] (ISIM).<ref name="isim">{{cite web|url=https://jwst.nasa.gov/isim.html|title=JWST: Integrated Science Instrument Module (ISIM)|publisher=NASA|date=2017|access-date=2 February 2017|archive-date=2 June 2019|archive-url=https://web.archive.org/web/20190602100607/https://www.jwst.nasa.gov/isim.html|url-status=live}} {{PD-notice}}</ref>

Cost growth revealed in spring 2005 led to an August 2005 re-planning.<ref name="replan"/> The primary technical outcomes of the re-planning were significant changes in the integration and test plans, a 22-month launch delay (from 2011 to 2013), and elimination of system-level testing for observatory modes at wavelengths shorter than 1.7&nbsp;μm. Other major features of the observatory were unchanged. Following the re-planning, the project was independently reviewed in April 2006.{{Citation needed|date=September 2022}}

In the 2005 re-plan, the life-cycle cost of the project was estimated at US$4.5 billion. This comprised approximately US$3.5 billion for design, development, launch and commissioning, and approximately US$1.0 billion for ten years of operations.<ref name="replan">{{cite web |author=Mather |first=John |title=James Webb Space Telescope (JWST) |url=http://www7.nationalacademies.org/bpa/CAA_Nov2005_Presentation_Mather.pdf |url-status=dead |archive-url=https://web.archive.org/web/20081110180605/http://www7.nationalacademies.org/bpa/CAA_Nov2005_Presentation_Mather.pdf |archive-date=10 November 2008 |access-date=5 July 2008 |publisher=National Academy of Science}} {{PD-notice}}</ref> The ESA agreed in 2004 to contributing about €300 million, including the launch.<ref name="ESA Media Relations Service">{{cite press release|url=http://www.esa.int/esaSC/Pr_10_2004_s_en.html|title=European agreement on James Webb Space Telescope's Mid-Infrared Instrument (MIRI) signed|date=9 June 2004|publisher=ESA Media Relations Service|access-date=6 May 2009|archive-date=18 May 2009|archive-url=https://web.archive.org/web/20090518064607/http://www.esa.int/esaSC/Pr_10_2004_s_en.html|url-status=dead}}</ref> The CSA pledged CA$39 million in 2007<ref>{{cite web|publisher=Canadian Space Agency|date=4 June 2007|title=Canada's contribution to NASA's James Webb Space Telescope|url=https://www.canada.ca/en/news/archive/2007/06/canada-contribution-nasa-james-webb-space-telescope.html|access-date=3 July 2021|website=canada.ca|archive-date=18 January 2022|archive-url=https://web.archive.org/web/20220118031434/https://www.canada.ca/en/news/archive/2007/06/canada-contribution-nasa-james-webb-space-telescope.html|url-status=live}}</ref> and in 2012 delivered its contributions in equipment to point the telescope and detect atmospheric conditions on distant planets.<ref>{{cite web|date=30 July 2012|title=Canadian Space Agency Delivers Canada's Contributions to the James Webb Space Telescope|url=https://spaceq.ca/canadian_space_agency_delivers_canadas_contributions_to_the_james_webb_space_telescope/|access-date=3 July 2021|website=SpaceQ|archive-date=18 January 2022|archive-url=https://web.archive.org/web/20220118031451/https://spaceq.ca/canadian_space_agency_delivers_canadas_contributions_to_the_james_webb_space_telescope/|url-status=live}}</ref>

=== Detailed design and construction (2007–2021) ===
{{multiple image
 | align       = vertical
 | total_width = 640
 | image1      = James Webb Space Telescope Mirror29.jpg
 | caption1    = A JWST mirror segment, 2010
 | image2      = James Webb Space Telescope Mirror37.jpg
 | caption2    = Mirror segments undergoing [[Cryogenics|cryogenic]] tests at the X-ray & Cryogenic Facility at [[Marshall Space Flight Center]]
 | image3      = NASA’s James Webb Space Telescope Completes Environmental Testing (50427670958) (cropped).jpg
 |caption3     = The assembled telescope following environmental testing
 }}

In January 2007, nine of the ten technology development items in the project successfully passed a Non-Advocate Review.<ref>{{cite web|url=http://www.stsci.edu/jwst/news/2007/jwst-passes-tnar|archive-url=https://archive.today/20120805232222/http://www.stsci.edu/jwst/news/2007/jwst-passes-tnar|url-status=dead|archive-date=5 August 2012|title=JWST Passes TNAR|publisher=STScI|access-date=5 July 2008}}</ref> These technologies were deemed sufficiently mature to retire significant risks in the project. The remaining technology development item (the [[MIRI (Mid-Infrared Instrument)|MIRI]] cryocooler) completed its technology maturation milestone in April 2007. This technology review represented the beginning step in the process that ultimately moved the project into its detailed design phase (Phase C). By May 2007, costs were still on target.<ref>{{cite web|url=http://www.space.com/businesstechnology/070523_techwed_jwst_dock.html|title=NASA Adds Docking Capability For Next Space Observatory|first=Brian|last=Berger|date=23 May 2007|website=SPACE.com|access-date=5 July 2008|archive-date=30 June 2008|archive-url=https://web.archive.org/web/20080630180805/http://www.space.com/businesstechnology/070523_techwed_jwst_dock.html|url-status=live}}</ref> In March 2008, the project successfully completed its Preliminary Design Review (PDR). In April 2008, the project passed the Non-Advocate Review. Other passed reviews include the [[Integrated Science Instrument Module]] review in March 2009, the [[Optical Telescope Element]] review completed in October 2009, and the Sunshield review completed in January 2010.<ref>{{cite web |title=James Webb Space Telescope sunshield is ready to fabricate |url=https://www.laserfocusworld.com/test-measurement/research/article/16568637/james-webb-space-telescope-sunshield-is-ready-to-fabricate |website=www.laserfocusworld.com |date=3 February 2010 |access-date=30 December 2021 |archive-date=30 December 2021 |archive-url=https://web.archive.org/web/20211230172444/https://www.laserfocusworld.com/test-measurement/research/article/16568637/james-webb-space-telescope-sunshield-is-ready-to-fabricate |url-status=live }}</ref>

In April 2010, the telescope passed the technical portion of its Mission Critical Design Review (MCDR). Passing the MCDR signified the integrated observatory can meet all science and engineering requirements for its mission.<ref>{{cite web|url=http://www.nasa.gov/home/hqnews/2010/apr/HQ_10-099_Webb_Telescope_Milestone.html|title=NASA's Webb Telescope Passes Key Mission Design Review Milestone|publisher=NASA|access-date=2 May 2010|archive-date=1 May 2010|archive-url=https://web.archive.org/web/20100501144204/http://www.nasa.gov/home/hqnews/2010/apr/HQ_10-099_Webb_Telescope_Milestone.html|url-status=live}} {{PD-notice}}</ref> The MCDR encompassed all previous design reviews. The project schedule underwent review during the months following the MCDR, in a process called the Independent Comprehensive Review Panel, which led to a re-plan of the mission aiming for a 2015 launch, but as late as 2018. By 2010, cost over-runs were impacting other projects, though Webb itself remained on schedule.<ref>{{cite web|url=http://www.spaceflightnow.com/news/n1008/12jwst/|title=NASA says JWST cost crunch impeding new missions|first=Stephen|last=Clark|publisher=Spaceflight Now|date=12 August 2010|access-date=13 August 2010|archive-date=29 April 2021|archive-url=https://web.archive.org/web/20210429114441/https://spaceflightnow.com/news/n1008/12jwst/|url-status=live}}</ref>

By 2011, the Webb project was in the final design and fabrication phase (Phase C).

Assembly of the hexagonal segments of the primary mirror, which was done via robotic arm, began in November 2015 and was completed on 3 February 2016. The secondary mirror was installed on 3 March 2016.<ref>{{cite web|url=https://www.nasa.gov/press-release/nasas-james-webb-space-telescope-primary-mirror-fully-assembled|title=NASA's James Webb Space Telescope Primary Mirror Fully Assembled|date=3 February 2016|website=nasa.gov|access-date=4 February 2016|archive-date=4 February 2016|archive-url=https://web.archive.org/web/20160204202435/https://www.nasa.gov/press-release/nasas-james-webb-space-telescope-primary-mirror-fully-assembled|url-status=live}} {{PD-notice}}</ref><ref>{{cite web|url=https://www.nasa.gov/feature/goddard/2016/nasas-james-webb-space-telescope-secondary-mirror-installed/|publisher=NASA|title=NASA's James Webb Space Telescope Secondary Mirror Installed|access-date=23 March 2016|date=7 March 2016|archive-date=17 March 2016|archive-url=https://web.archive.org/web/20160317190252/http://www.nasa.gov/feature/goddard/2016/nasas-james-webb-space-telescope-secondary-mirror-installed/|url-status=live}} {{PD-notice}}</ref> Final construction of the Webb telescope was completed in November 2016, after which extensive testing procedures began.<ref>{{cite web|url=https://www.theguardian.com/science/2016/nov/04/nasa-testing-james-webb-space-telescope-gold|title=Nasa begins testing enormous space telescope made of gold mirrors|newspaper=The Guardian|first=Alan|last=Yuhas|date=4 November 2016|access-date=5 November 2016|archive-date=5 November 2016|archive-url=https://web.archive.org/web/20161105135156/https://www.theguardian.com/science/2016/nov/04/nasa-testing-james-webb-space-telescope-gold|url-status=live}}</ref>

In March 2018, NASA delayed Webb's launch an additional two years to May 2020 after the telescope's sunshield ripped during a practice deployment and the sunshield's cables did not sufficiently tighten. In June 2018, NASA delayed the launch by an additional 10 months to March 2021, based on the assessment of the independent review board convened after the failed March 2018 test deployment.<ref name="NASAJWSTdelay2021">{{cite news|date=27 June 2018|title=NASA Completes Webb Telescope Review, Commits to Launch in Early 2021|publisher=NASA|url=https://www.nasa.gov/press-release/nasa-completes-webb-telescope-review-commits-to-launch-in-early-2021|access-date=27 June 2018|archive-date=14 March 2020|archive-url=https://web.archive.org/web/20200314025315/https://www.nasa.gov/press-release/nasa-completes-webb-telescope-review-commits-to-launch-in-early-2021|url-status=live}} {{PD-notice}}</ref> The review identified that Webb launch and deployment had 344 potential [[single-point failure]]s – tasks that had no alternative or means of recovery if unsuccessful, and therefore had to succeed for the telescope to work.<ref>{{cite web|url=https://www.washingtonpost.com/news/speaking-of-science/wp/2018/07/26/northrop-grumman-ceo-is-grilled-about-james-webb-space-telescope-errors/|title=Northrop Grumman CEO is grilled about James Webb Space Telescope errors|last=Achenbach|first=Joel|date=26 July 2018|newspaper=The Washington Post|access-date=28 December 2019|archive-date=28 December 2019|archive-url=https://web.archive.org/web/20191228145204/https://www.washingtonpost.com/news/speaking-of-science/wp/2018/07/26/northrop-grumman-ceo-is-grilled-about-james-webb-space-telescope-errors/|url-status=live}}</ref> In August 2019, the mechanical integration of the telescope was completed, something that was scheduled to be done 12 years before in 2007.<ref>{{cite web|url=https://www.businessinsider.in/nasa-hubble-telescope-replacement-james-webb-space-telescope-assembled-after-12-years/articleshow/70886209.cms|title=The two halves of Hubble's US$10 billion successor have finally come together after 12 years of waiting|work=Business Insider |access-date=29 August 2019|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144438/https://www.businessinsider.in/nasa-hubble-telescope-replacement-james-webb-space-telescope-assembled-after-12-years/articleshow/70886209.cms|url-status=live}}</ref>

After construction was completed, Webb underwent final tests at Northrop Grumman's historic [[Space Park]] in Redondo Beach, California.<ref>{{cite web|last=Clark|first=Stephen|date=30 September 2021|title=After two decades, the Webb telescope is finished and on the way to its launch site|url=https://spaceflightnow.com/2021/09/30/webb-on-the-way-to-french-guiana/|website=Spaceflight Now|access-date=6 October 2021|archive-date=6 October 2021|archive-url=https://web.archive.org/web/20211006070009/https://spaceflightnow.com/2021/09/30/webb-on-the-way-to-french-guiana/|url-status=live}}</ref> A ship carrying the telescope left California on 26 September 2021, passed through the [[Panama Canal]], and arrived in [[French Guiana]] on 12 October 2021.<ref>{{cite web|last=Wall|first=Mike|date=12 October 2021|title=NASA's James Webb Space Telescope arrives in French Guiana ahead of December 18 launch|url=https://www.space.com/nasa-james-webb-space-telescope-arrives-french-guiana|website=Space.com|access-date=13 October 2021|archive-date=12 October 2021|archive-url=https://web.archive.org/web/20211012234511/https://www.space.com/nasa-james-webb-space-telescope-arrives-french-guiana|url-status=live}}</ref>

=== Cost and schedule issues {{anchor|Time, budget}} ===
NASA's lifetime cost for the project is{{When|date=September 2022}} expected to be US$9.7 billion, of which US$8.8 billion was spent on spacecraft design and development and US$861 million is planned to support five years of mission operations.<ref>{{cite web|title=FY 2022 NASA Congressional Budget Justification|url=https://www.nasa.gov/sites/default/files/atoms/files/fy2022_congressional_justification_nasa_budget_request.pdf|publisher=NASA|page=JWST-2|access-date=21 October 2021|archive-date=10 June 2021|archive-url=https://web.archive.org/web/20210610114215/https://www.nasa.gov/sites/default/files/atoms/files/fy2022_congressional_justification_nasa_budget_request.pdf|url-status=live}} {{PD-notice}}</ref> Representatives from ESA and CSA stated their project contributions amount to approximately €700&nbsp;million and CA$200 million, respectively.<ref>{{cite news|last1=Foust|first1=Jeff|title=JWST launch slips to November|url=https://spacenews.com/jwst-launch-slips-to-november/|publisher=SpaceNews|date=2 June 2021|access-date=21 October 2021|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144437/https://spacenews.com/jwst-launch-slips-to-november/|url-status=live}}</ref>

A study in 1984 by the Space Science Board estimated that to build a next-generation infrared observatory in orbit would cost US$4 billion (US$7B in 2006 dollars, or $10B in 2020 dollars).<ref name="nature06" /> While this came close to the final cost of Webb, the first NASA design considered in the late 1990s was more modest, aiming for a $1&nbsp;billion price tag over 10 years of construction. Over time this design expanded, added funding for contingencies, and had scheduling delays.

{| class="wikitable" style="float:right; margin-left:0.5em; font-size:0.9em;"
|+ Progression of estimates for schedule and cost, along with major milestones
|-
! Year
! Planned<br />launch
! Budget plan<br /><small>(billion USD)</small>
|-
| 1998 || 2007<ref>{{cite web|last1=Lilly|first1=Simon|url=http://www.casca.ca/lrp/vol2/ngst/hstng.html|title=The Next Generation Space Telescope (NGST)|publisher=University of Toronto|date=27 November 1998|access-date=23 August 2011|archive-date=25 December 2021|archive-url=https://web.archive.org/web/20211225224535/https://www.casca.ca/lrp/vol2/ngst/hstng.html|url-status=live}}</ref>|| 1<ref name="nature06" />
|-
| 2000 || 2009<ref name="miri">{{cite web|url=http://www.astron.nl/miri-ngst/old/public/science/phase-a/text.htm|title=MIRI spectrometer for NGST|url-status=dead| archive-url=https://web.archive.org/web/20110927053021/http://www.astron.nl/miri-ngst/old/public/science/phase-a/text.htm|archive-date=27 September 2011}}</ref> || 1.8<ref name="nature06"/>
|-
| 2002 || 2010<ref>{{cite web|url=http://www.spaceref.com/news/viewsr.html?pid=5319|title=NGST Weekly Missive|date=25 April 2002|access-date=23 August 2011|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144440/https://spaceref.com/status-report/ngst-weekly-missive-25-apr-2002/|url-status=live}}</ref> || 2.5<ref name="nature06"/>
|-
| 2003 || 2011<ref>{{cite web|url=http://www.nasa.gov/home/hqnews/2003/nov/HQ_c03pp_telescope_mod.html|title=NASA Modifies James Webb Space Telescope Contract|date=12 November 2003|access-date=23 August 2011|archive-date=25 December 2021|archive-url=https://web.archive.org/web/20211225224505/https://www.nasa.gov/home/hqnews/2003/nov/HQ_c03pp_telescope_mod.html|url-status=live}} {{PD-notice}}</ref> || 2.5<ref name="nature06">{{cite journal|title=US astronomy: Is the next big thing too big?|first=Tony|last=Reichhardt|date=March 2006|journal=Nature|volume=440|issue=7081|doi=10.1038/440140a|pmid=16525437|pages=140–143|bibcode=2006Natur.440..140R|doi-access=free}}</ref>
|-
| 2005 || 2013 || 3<ref>{{cite web|url=http://www.spacepolitics.com/2005/05/21/problems-for-jwst/|title=Problems for JWST|date=21 May 2005|access-date=25 August 2011|archive-date=25 December 2021|archive-url=https://web.archive.org/web/20211225224620/http://www.spacepolitics.com/2005/05/21/problems-for-jwst/|url-status=live}}</ref>
|-
| 2006 || 2014 || 4.5<ref>{{cite journal|title=Refocusing NASA's vision|journal=Nature|date=9 March 2006|volume=440|issue=7081|doi=10.1038/440127a|pmid=16525425|page=127|bibcode=2006Natur.440..127.|doi-access=free}}</ref>
|-
|colspan=3 style="text-align:center"|2008: Preliminary Design Review
|-
| 2008 || 2014 || 5.1<ref name="cowen">{{cite web|url=http://news.sciencemag.org/scienceinsider/2011/08/webb-telescope-delayed-costs.html?ref=hp|first=Ron|last=Cowen|title=Webb Telescope Delayed, Costs Rise to $8 Billion|date=25 August 2011|publisher=ScienceInsider|url-status=dead|archive-url=https://web.archive.org/web/20120114105805/http://news.sciencemag.org/scienceinsider/2011/08/webb-telescope-delayed-costs.html?ref=hp|archive-date=14 January 2012}}</ref>
|-
|colspan=3 style="text-align:center"|2010: Critical Design Review
|-
| 2010 || 2015 to 2016 || 6.5<ref name="499224main_JWST-ICRP_Report-FINAL"/>
|-
| 2011 || 2018 || 8.7<ref name="price">{{cite news|url=https://www.bbc.co.uk/news/science-environment-14625362|first=Jonathan|last=Amos|title=JWST price tag now put at over $8 bn|publisher=BBC|date=22 August 2011|access-date=22 June 2018|archive-date=25 December 2021|archive-url=https://web.archive.org/web/20211225224448/https://www.bbc.co.uk/news/science-environment-14625362|url-status=live}}</ref>
|-
| 2017 || 2019<ref name="launch 2019">{{cite web|url=https://www.nasa.gov/feature/nasa-s-james-webb-space-telescope-to-be-launched-spring-2019|title=NASA's James Webb Space Telescope to be Launched Spring 2019|publisher=NASA|date=28 September 2017|access-date=28 September 2017|archive-date=7 February 2018|archive-url=https://web.archive.org/web/20180207135912/https://www.nasa.gov/feature/nasa-s-james-webb-space-telescope-to-be-launched-spring-2019/|url-status=live}} {{PD-notice}}</ref> || 8.8
|-
| 2018 || 2020<ref name=":0">{{cite news|url=https://www.space.com/40102-james-webb-space-telescope-launch-delay-2020.html|title=NASA Delays Launch of James Webb Space Telescope to 2020|publisher=Space.com|access-date=27 March 2018|archive-date=28 April 2022|archive-url=https://web.archive.org/web/20220428191901/https://www.space.com/40102-james-webb-space-telescope-launch-delay-2020.html|url-status=live}}</ref> || ≥8.8
|-
| 2019 || March 2021<ref>{{cite web|url=https://www.nasa.gov/press-release/nasa-completes-webb-telescope-review-commits-to-launch-in-early-2021|title=NASA Completes Webb Telescope Review, Commits to Launch in Early 2021|publisher=NASA|website=nasa.gov|date=27 June 2018|access-date=28 June 2018|archive-date=14 March 2020|archive-url=https://web.archive.org/web/20200314025315/https://www.nasa.gov/press-release/nasa-completes-webb-telescope-review-commits-to-launch-in-early-2021|url-status=live}} {{PD-notice}}</ref> || 9.66
|-
| 2021 || Dec 2021<ref>{{cite web|url=https://spaceflightnow.com/2021/12/14/nasa-delays-launch-of-webb-telescope-to-no-earlier-than-dec-24/|title=NASA delays launch of Webb telescope to no earlier than Dec. 24|date=14 December 2021|access-date=14 December 2021|archive-date=15 December 2021|archive-url=https://web.archive.org/web/20211215014428/https://spaceflightnow.com/2021/12/14/nasa-delays-launch-of-webb-telescope-to-no-earlier-than-dec-24/|url-status=live}} {{PD-notice}}</ref> || 9.70
|}

By 2008, when the project entered preliminary design review and was formally confirmed for construction, over US$1 billion had already been spent on developing the telescope, and the total budget was estimated at US$5 billion (equivalent to ${{Inflation|US|5|2005|r=2}}&nbsp;billion in {{Inflation/year|US}}).{{inflation/fn|US}} In summer 2010, the mission passed its Critical Design Review (CDR) with excellent grades on all technical matters, but schedule and cost slips at that time prompted Maryland U.S. Senator [[Barbara Mikulski]] to call for external review of the project. The Independent Comprehensive Review Panel (ICRP) chaired by J. Casani (JPL) found that the earliest possible launch date was in late 2015 at an extra cost of US$1.5 billion (for a total of US$6.5 billion). They also pointed out that this would have required extra funding in FY2011 and FY2012 and that any later launch date would lead to a higher total cost.<ref name="499224main_JWST-ICRP_Report-FINAL">{{cite web|url=http://www.nasa.gov/pdf/499224main_JWST-ICRP_Report-FINAL.pdf|title=Independent Comprehensive Review Panel, Final Report|date=29 October 2010|access-date=10 June 2011|archive-date=17 November 2021|archive-url=https://web.archive.org/web/20211117185346/https://www.nasa.gov/pdf/499224main_JWST-ICRP_Report-FINAL.pdf|url-status=live}} {{PD-notice}}</ref>

On 6 July 2011, the United States House of Representatives' appropriations committee on Commerce, Justice, and Science moved to cancel the James Webb project by proposing an FY2012 budget that removed US$1.9 billion from NASA's overall budget, of which roughly one quarter was for Webb.<ref name="guardian.co.uk">{{cite news|url=https://www.theguardian.com/science/2011/jul/09/nasa-james-webb-space-telescope|title=Nasa fights to save the James Webb space telescope from the axe|newspaper=The Guardian|location=London|first=Robin|last=McKie|date=9 July 2011|access-date=14 December 2016|archive-date=17 March 2017|archive-url=https://web.archive.org/web/20170317210545/https://www.theguardian.com/science/2011/jul/09/nasa-james-webb-space-telescope|url-status=live}}</ref><ref>{{cite web|url=http://appropriations.house.gov/news/DocumentSingle.aspx?DocumentID=250023|title=Appropriations Committee Releases the Fiscal Year 2012 Commerce, Justice, Science Appropriations|publisher=US House of representatives Committee on Appropriations|date=6 July 2011|access-date=7 July 2011|archive-date=23 March 2012|archive-url=https://web.archive.org/web/20120323111945/http://appropriations.house.gov/News/DocumentSingle.aspx?DocumentID=250023|url-status=live}} {{PD-notice}}</ref><ref>{{cite web|url=http://www.spacedaily.com/reports/US_lawmakers_vote_to_kill_Hubble_successor_999.html|title=US lawmakers vote to kill Hubble successor|publisher=SpaceDaily|date=7 July 2011|access-date=8 July 2011|archive-date=10 July 2011|archive-url=https://web.archive.org/web/20110710020814/http://www.spacedaily.com/reports/US_lawmakers_vote_to_kill_Hubble_successor_999.html|url-status=live}}</ref><ref>{{cite web|url=http://www.space.com/12187-nasa-budget-bill-cancels-space-telescope-house.html|title=Proposed NASA Budget Bill Would Cancel Major Space Telescope|publisher=Space.com|date=6 July 2011|access-date=11 July 2011|archive-date=9 July 2011|archive-url=https://web.archive.org/web/20110709024728/http://www.space.com/12187-nasa-budget-bill-cancels-space-telescope-house.html|url-status=live}}</ref> US$3 billion had been spent and 75% of its hardware was in production.<ref>{{cite web|last1=Bergin|first1=Chris|title=James Webb Space Telescope hardware entering key test phase|url=http://www.nasaspaceflight.com/2015/01/jwst-hardware-entering-test-phase/|publisher=NASASpaceFlight.com|date=7 January 2015|access-date=28 August 2016|archive-date=7 November 2017|archive-url=https://web.archive.org/web/20171107152854/https://www.nasaspaceflight.com/2015/01/jwst-hardware-entering-test-phase/|url-status=live}}</ref> This budget proposal was approved by subcommittee vote the following day. The committee charged that the project was "billions of dollars over budget and plagued by poor management".<ref name="guardian.co.uk"/> In response, the [[American Astronomical Society]] issued a statement in support of Webb,<ref>{{cite web|url=https://aas.org/media/press-releases/aas-issues-statement-proposed-cancellation-james-webb-space-telescope|title=AAS Issues Statement on Proposed Cancellation of James Webb Space Telescope|last=Hand|first=E.|date=7 July 2011|publisher=American Astronomical Society|access-date=1 February 2017|archive-date=19 March 2018|archive-url=https://web.archive.org/web/20180319213552/https://aas.org/media/press-releases/aas-issues-statement-proposed-cancellation-james-webb-space-telescope|url-status=live}}</ref> as did Senator Mikulski.<ref>{{cite web|url=http://www.spaceref.com/news/viewpr.html?pid=34063|title=Mikulski Statement on House Appropriations Subcommittee Termination of James Webb Telescope|work=SpaceRef|date=11 July 2011|access-date=1 February 2017|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144441/https://spaceref.com/press-release/mikulski-statement-on-house-appropriations-subcommittee-termination-of-james-webb-space-telescope/|url-status=live}}</ref> A number of editorials supporting Webb appeared in the international press during 2011 as well.<ref name="guardian.co.uk"/><ref>{{cite news|title=Way Above the Shuttle Flight|date=9 July 2011|newspaper=The New York Times|url=https://www.nytimes.com/2011/07/10/opinion/sunday/10sun2.html?ref=opinion|access-date=27 February 2017|archive-date=19 March 2018|archive-url=https://web.archive.org/web/20180319214529/http://www.nytimes.com/2011/07/10/opinion/sunday/10sun2.html?ref=opinion|url-status=live}}</ref><ref>{{cite web|last=Harrold|first=Max|date=7 July 2011|title=Bad news for Canada: U.S. could scrap new space telescope|newspaper=The Vancouver Sun|url=https://vancouversun.com/technology/space-shuttle/news+Canada+could+scrap+space+telescope/5067942/story.html|access-date=27 January 2019|archive-date=31 July 2018|archive-url=https://web.archive.org/web/20180731183330/http://www.vancouversun.com/technology/space-shuttle/news+Canada+could+scrap+space+telescope/5067942/story.html|url-status=live}}</ref> In November 2011, Congress reversed plans to cancel Webb and instead capped additional funding to complete the project at US$8 billion.<ref>{{cite news |title=NASA budget plan saves telescope, cuts space taxis |url=https://www.reuters.com/article/us-usa-space-budget-idUSTRE7AF06320111116 |work=Reuters|date=16 November 2011|access-date=1 July 2017|archive-date=24 September 2015|archive-url=https://web.archive.org/web/20150924160524/http://www.reuters.com/article/2011/11/16/us-usa-space-budget-idUSTRE7AF06320111116 |url-status=live}}</ref>

While similar issues had affected other major NASA projects such as the Hubble telescope, some scientists expressed concerns about growing costs and schedule delays for the Webb telescope, worrying that its budget might be competing with those of other space science programs.<ref name="SpaceNov12">{{cite news|url=http://www.space.com/13528-nasa-jwst-telescope-funding-delay-science-missions.html|title=NASA Acknowledges James Webb Telescope Costs Will Delay Other Science Missions|first=Dan|last=Leone|publisher=SpaceNews|date=7 November 2012|access-date=12 January 2013|archive-date=22 January 2013|archive-url=https://web.archive.org/web/20130122080648/http://www.space.com/13528-nasa-jwst-telescope-funding-delay-science-missions.html|url-status=live}}</ref><ref name="sciam15">{{cite web |last=Moskowitz |first=Clara |date=30 March 2015 |title=NASA Assures Skeptical Congress That the James Webb Telescope Is on Track |url=https://www.scientificamerican.com/article/nasa-assures-skeptical-congress-that-the-james-webb-telescope-is-on-track/ |access-date=29 January 2017 |publisher=Scientific American |archive-date=2 February 2017 |archive-url=https://web.archive.org/web/20170202070132/https://www.scientificamerican.com/article/nasa-assures-skeptical-congress-that-the-james-webb-telescope-is-on-track/ |url-status=live }}</ref> A 2010 ''Nature'' article described Webb as "the telescope that ate astronomy".<ref>{{cite journal|title=The telescope that ate astronomy|journal=Nature|volume=467|issue=7319|pages=1028–1030|date=27 October 2010|doi=10.1038/4671028a|pmid=20981068 |last1=Billings|first1=Lee|doi-access=free}}</ref> NASA continued to defend the budget and timeline of the program to Congress.<ref name="sciam15" /><ref name="atlantic">{{cite web|url=https://www.theatlantic.com/science/archive/2016/12/james-webb-space-telescope-goddard/509840/|title=The Extreme Hazing of the Most Expensive Telescope Ever Built|last=Koren|first=Marina|date=7 December 2016|publisher=The Atlantic|access-date=29 January 2017|archive-date=2 February 2017|archive-url=https://web.archive.org/web/20170202065139/https://www.theatlantic.com/science/archive/2016/12/james-webb-space-telescope-goddard/509840/|url-status=live}}</ref>

In 2018, [[Gregory L. Robinson]] was appointed as the new director of the Webb program.<ref name=":02">{{Cite news |last=Cohen |first=Ben |date=2022-07-08 |title=The NASA Engineer Who Made the James Webb Space Telescope Work |language=en-US |work=[[The Wall Street Journal]] |url=https://www.wsj.com/articles/nasa-james-webb-space-telescope-greg-robinson-images-11657137487 |url-status=live |access-date=2022-07-12 |archive-url=https://web.archive.org/web/20220711105706/https://www.wsj.com/articles/nasa-james-webb-space-telescope-greg-robinson-images-11657137487 |archive-date=2022-07-11 |issn=0099-9660}}</ref> Robinson was credited with raising the program's schedule efficiency (how many measures were completed on time) from 50% to 95%.<ref name=":02" /> For his role in improving the performance of the Webb program, Robinsons's supervisor, [[Thomas Zurbuchen]], called him "the most effective leader of a mission I have ever seen in the history of NASA".<ref name=":02" /> In July 2022, after Webb's commissioning process was complete and it began transmitting its first data, Robinson retired following a 33-year career at NASA.<ref>{{Cite web |last=Potter |first=Sean |date=2022-07-22 |title=NASA Webb Program Director Greg Robinson Announces Retirement |url=http://www.nasa.gov/feature/nasa-webb-program-director-greg-robinson-announces-retirement |access-date=2022-07-22 |website=NASA |archive-date=23 July 2022 |archive-url=https://web.archive.org/web/20220723123416/https://www.nasa.gov/feature/nasa-webb-program-director-greg-robinson-announces-retirement/ |url-status=live }}</ref>

On 27 March 2018, NASA pushed back the launch to May 2020 or later,<ref name=":0" /> with a final cost estimate to come after a new launch window was determined with the ESA.<ref name="NASA-20180327">{{cite news|url=https://www.nasa.gov/press-release/nasa-s-webb-observatory-requires-more-time-for-testing-and-evaluation-new-launch|title=NASA's Webb Observatory Requires More Time for Testing and Evaluation|last1=Wang|first1=Jen Rae|last2=Cole|first2=Steve|last3=Northon|first3=Karen|date=27 March 2018|publisher=NASA|access-date=27 March 2018|archive-date=29 March 2018|archive-url=https://web.archive.org/web/20180329030036/https://www.nasa.gov/press-release/nasa-s-webb-observatory-requires-more-time-for-testing-and-evaluation-new-launch|url-status=live}} {{PD-notice}}</ref><ref>{{cite news|url=https://www.bbc.com/news/science-environment-43559980|title=Hubble 'successor' faces new delay|last=Amos|first=Jonathan|date=27 March 2018|work=BBC News|access-date=27 March 2018|archive-date=28 March 2018|archive-url=https://web.archive.org/web/20180328001344/http://www.bbc.com/news/science-environment-43559980|url-status=live}}</ref><ref>{{cite journal|title=NASA reveals major delay for $8-billion Hubble successor|last=Witze|first=Alexandra|journal=Nature|doi=10.1038/d41586-018-03863-5|doi-access=free|bibcode=2018Natur.556...11W|date=27 March 2018|volume=556|issue=7699|pages=11–12|pmid=29620740 }}</ref> In 2019, its mission cost cap was increased by US$800 million.<ref>{{cite news |last=Dreier |first=Casey |date=15 February 2019 |title=NASA just got its best budget in a decade |url=http://www.planetary.org/blogs/casey-dreier/2019/0215-fy2019-nasa-gets-its-best-budget-in-decades.html |access-date=7 March 2019 |archive-date=16 February 2019 |archive-url=https://web.archive.org/web/20190216012055/http://www.planetary.org/blogs/casey-dreier/2019/0215-fy2019-nasa-gets-its-best-budget-in-decades.html |url-status=live }}</ref> After launch windows were paused in 2020 due to the [[COVID-19 pandemic]],<ref name="cvdly">{{cite news|url=https://spacenews.com/coronavirus-pauses-work-on-jwst/|title=Coronavirus pauses work on JWST|date=20 March 2020|first=Jeff|last=Foust|work=SpaceNews|access-date=15 April 2020|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144438/https://spacenews.com/coronavirus-pauses-work-on-jwst/|url-status=live}}</ref> Webb was launched at the end of 2021, with a total cost of just under US$10 billion.

No single area drove the cost. For future large telescopes, there are five major areas critical to controlling overall cost:<ref>{{Cite web |last1=Feinberg |first1=Lee |last2=Arenberg |first2=J. |last3=Lightsey |first3=P. |last4=Yanatsis |first4=D. |title=Breaking the cost curve: applying lessons learned from the James Webb Space Telescope development |url=https://ntrs.nasa.gov/api/citations/20190001891/downloads/20190001891.pdf |access-date=2024-03-01 |website=NASA Technical Reports Server}}</ref>
* System complexity
* Critical path and [[Overhead (business)|overhead]]
* Verification challenges
* Programmatic constraints
* Early integration and test considerations

=== Partnership ===
NASA, ESA and CSA have collaborated on the telescope since 1996. ESA's participation in construction and launch was approved by its members in 2003 and an agreement was signed between ESA and NASA in 2007. In exchange for full partnership, representation and access to the observatory for its astronomers, ESA is providing the NIRSpec instrument, the Optical Bench Assembly of the MIRI instrument, an [[Ariane 5|Ariane 5 ECA]] launcher, and manpower to support operations.<ref name="ESA Media Relations Service"/><ref>{{cite web|url=https://sci.esa.int/web/jwst/-/45728-europe-s-role|title=ESA Science & Technology – Europe's Contributions to the JWST Mission|website=European Space Agency|access-date=19 December 2021|archive-date=19 March 2022|archive-url=https://web.archive.org/web/20220319004958/https://sci.esa.int/web/jwst/-/45728-europe-s-role|url-status=live}}</ref> The CSA provided the Fine Guidance Sensor and the Near-Infrared Imager Slitless Spectrograph and manpower to support operations.<ref>{{cite web |url=http://www.asc-csa.gc.ca/eng/media/news_releases/2012/0730.asp |title=Canadian Space Agency 'Eyes' Hubble's Successor: Canada Delivers its Contribution to the World's Most Powerful Space Telescope |publisher=Canadian Space Agency |date=12 April 2013 |archive-url=https://web.archive.org/web/20130412124143/http://www.asc-csa.gc.ca/eng/media/news_releases/2012/0730.asp |archive-date=12 April 2013 |url-status=dead}}</ref>

Several thousand scientists, engineers, and technicians spanning 15 countries have contributed to the build, test and integration of Webb.<ref name="jenner010620">{{cite web|last=Jenner|first=Lynn|date=1 June 2020|title=NASA's Webb Telescope is an International Endeavor|url=http://www.nasa.gov/feature/goddard/2020/nasa-s-webb-telescope-is-an-international-endeavor|access-date=23 September 2021|website=NASA|archive-date=19 March 2022|archive-url=https://web.archive.org/web/20220319062122/https://www.nasa.gov/feature/goddard/2020/nasa-s-webb-telescope-is-an-international-endeavor/|url-status=live}}</ref> A total of 258 companies, government agencies, and academic institutions participated in the pre-launch project; 142 from the United States, 104 from 12 European countries (including 21 from the U.K., 16 from France, 12 from Germany and 7 international),<ref name="jwst_team">{{Cite web |title=Institutional Partners Webb/NASA |url=https://jwst.nasa.gov/content/meetTheTeam/team.html |access-date=2023-08-02 |website=jwst.nasa.gov |date=19 July 2023 |language=en}}</ref> and 12 from Canada.<ref name="jenner010620"/> Other countries as NASA partners, such as Australia, were involved in post-launch operation.<ref>{{cite news |last1=Shepherd |first1=Tony |title=James Webb: world's most powerful telescope makes its first call to Australia on Christmas Day |url=https://www.theguardian.com/science/2021/dec/25/james-webb-worlds-most-powerful-telescope-makes-its-first-call-to-australia-on-christmas-day |access-date=5 January 2022 |work=The Guardian |date=25 December 2021 |language=en |archive-date=19 March 2022 |archive-url=https://web.archive.org/web/20220319004958/https://www.theguardian.com/science/2021/dec/25/james-webb-worlds-most-powerful-telescope-makes-its-first-call-to-australia-on-christmas-day |url-status=live }}</ref>

Participating countries:
{{div col|colwidth=12em}}
* {{flagcountry|Austria}}
* {{flagcountry|Belgium}}
* {{flagcountry|Canada}}
* {{flagcountry|Czechia}}
* {{flagcountry|Denmark}}
* {{flagcountry|Finland}}
* {{flagcountry|France}}
* {{flagcountry|Germany}}
* {{flagcountry|Greece}}
* {{flagcountry|Ireland}}
* {{flagcountry|Italy}}
* {{flagcountry|Luxembourg}}
* {{flagcountry|Netherlands}}
* {{flagcountry|Norway}}
* {{flagcountry|Portugal}}
* {{flagcountry|Spain}}
* {{flagcountry|Sweden}}
* {{flagcountry|Switzerland}}
* {{flagcountry|United Kingdom}}
* {{flagcountry|United States}}
{{div col end}}

=== Naming concerns ===
{{See also|James E. Webb#NASA|James E. Webb#Legacy}}
In 2002, NASA administrator (2001–2004) [[Sean O'Keefe]] made the decision to name the telescope after [[James E. Webb]], the administrator of NASA from 1961 to 1968 during the [[Project Mercury|Mercury]], [[Project Gemini|Gemini]], and much of the [[Apollo program]]s.<ref name="nameannounce" /><ref name=":4" />

In 2015, concerns were raised around Webb's possible role in the [[lavender scare]], the mid-20th-century persecution by the U.S. government targeting [[Homosexuality|homosexuals]] in [[Federal government of the United States|federal employment]].<ref>{{cite web |last=Francis |first=Matthew |title=The Problem With Naming Observatories For Bigots |url=https://www.forbes.com/sites/matthewfrancis/2015/06/11/the-problem-with-naming-observatories-for-bigots/ |access-date=2022-04-11 |website=Forbes |language=en |archive-date=11 April 2022 |archive-url=https://web.archive.org/web/20220411042530/https://www.forbes.com/sites/matthewfrancis/2015/06/11/the-problem-with-naming-observatories-for-bigots/ |url-status=live }}</ref><ref>{{cite web |date=21 January 2015 |first=Dan |last=Savage |title=Should NASA Name a Telescope After a Dead Guy Who Persecuted Gay People in the 1950s? |url=http://slog.thestranger.com/slog/archives/2015/01/21/should-nasa-name-a-telescope-after-a-dead-guy-who-persecuted-gay-people-in-the-1950s |access-date=2022-04-11 |website=The Stranger |language=en |archive-date=24 January 2015 |archive-url=https://web.archive.org/web/20150124072342/http://slog.thestranger.com/slog/archives/2015/01/21/should-nasa-name-a-telescope-after-a-dead-guy-who-persecuted-gay-people-in-the-1950s |url-status=live }}</ref> In 2022, NASA released a report of an investigation,<ref>{{cite web |last1=Fisher |first1=Alise |title=NASA Shares James Webb History Report |url=https://www.nasa.gov/feature/nasa-shares-james-webb-history-report |website=NASA |access-date=25 November 2022 |date=18 November 2022 |archive-date=24 November 2022 |archive-url=https://web.archive.org/web/20221124083102/https://www.nasa.gov/feature/nasa-shares-james-webb-history-report/ |url-status=live }}</ref> based on an examination of more than 50,000 documents. The report found "no available evidence directly links Webb to any actions or follow-up related to the firing of individuals for their sexual orientation", either in his time in the State Department or at NASA.<ref>{{cite web |last1=Odom |first1=Brian C. |title=NASA Historical Investigation into James E. Webb's Relationship to the Lavender Scare. Final Report |url=https://www.nasa.gov/sites/default/files/atoms/files/nasa_historical_investigation_james_webb_0.pdf |website=nasa.gov |publisher=NASA |access-date=25 November 2022 |archive-date=24 November 2022 |archive-url=https://web.archive.org/web/20221124093857/https://www.nasa.gov/sites/default/files/atoms/files/nasa_historical_investigation_james_webb_0.pdf |url-status=live }}</ref><ref>{{cite journal |author=Witze |first=Alexandra |date=18 November 2022 |title=NASA really, really won't rename Webb telescope despite community pushback |url=https://www.nature.com/articles/d41586-022-03787-1 |url-status=live |journal=Nature |doi=10.1038/d41586-022-03787-1 |pmid=36400961 |s2cid=253671586 |archive-url=https://web.archive.org/web/20221122182645/https://www.nature.com/articles/d41586-022-03787-1 |archive-date=22 November 2022 |accessdate=21 November 2022|url-access=subscription }}</ref>

== Mission goals ==
The James Webb Space Telescope has four key goals:
* to search for light from the first stars and galaxies that formed in the universe after the Big Bang
* to study [[galaxy formation and evolution]]
* to understand [[star formation]] and [[planet formation]]
* to study planetary systems and the [[Abiogenesis|origins of life]]<ref>{{cite web |last1=Masetti |first1=Maggie |last2=Krishnamurthi |first2=Anita |date=2009 |title=JWST Science |url=http://www.jwst.nasa.gov/science.html |url-status=live |archive-url=https://web.archive.org/web/20171124152624/https://jwst.nasa.gov/science.html |archive-date=24 November 2017 |access-date=14 April 2013 |publisher=NASA |language=en-us}} {{PD-notice}}</ref>

These goals can be accomplished more effectively by observation in near-infrared light rather than light in the visible part of the spectrum. For this reason, Webb's instruments will not measure visible or ultraviolet light like the Hubble Telescope, but will have a much greater capacity to perform [[infrared astronomy]]. Webb will be sensitive to a range of wavelengths from 0.6 to 28&nbsp;μm (corresponding respectively to orange light and deep infrared radiation at about {{cvt|100|K|C|disp=or}}).

Webb may be used to gather information on the dimming light of star [[Tabby's Star|KIC 8462852]], which was discovered in 2015, and has some abnormal light-curve properties.<ref>{{cite web|url=http://www.popularmechanics.com/space/telescopes/a19346/james-webb-telescope-alien-megastructure/|title=NASA's Next Telescope Could ID Alien Megastructures|date=9 February 2016|access-date=1 September 2016|archive-date=9 October 2019|archive-url=https://web.archive.org/web/20191009124137/https://www.popularmechanics.com/space/telescopes/a19346/james-webb-telescope-alien-megastructure/|url-status=live}}</ref>

Additionally, it will be able to tell if an exoplanet has methane in its atmosphere, allowing astronomers to determine whether or not the methane is a [[biosignature]].<ref name="NYT-20220702">{{cite news |last=Zimmer |first=Carl |author-link=Carl Zimmer |title=Webb Telescope Will Look for Signs of Life Way Out There – The first question astronomers want to answer about exoplanets: Do they have atmospheres friendly to life? |url=https://www.nytimes.com/2022/07/02/science/webb-telescope-exoplanets-atmosphere.html |date=2 July 2022 |work=[[The New York Times]] |access-date=2 July 2022 |archive-date=2 July 2022 |archive-url=https://web.archive.org/web/20220702090649/https://www.nytimes.com/2022/07/02/science/webb-telescope-exoplanets-atmosphere.html/ |url-status=live }}</ref><ref>{{Cite web |last=updated |first=Stefanie Waldek last |date=2022-03-29 |title=NASA's new James Webb Space Telescope will be able to sniff out methane. Here's how to tell if it's a sign of life. |url=https://www.space.com/methane-biosignature-search-for-life-cautions |access-date=2023-08-02 |website=Space.com |language=en}}</ref>

=== Orbit design ===
[[File:L2 rendering.jpg|thumb|upright=1.4|right|Webb is not exactly at the {{L2|nolink=yes}} point, but circles around it in a [[halo orbit]].]]
[[File:Carina Nebula in Visible and Infrared.jpg|thumb|upright=1.4|right|Alternative [[Hubble Space Telescope]] views of the [[Carina Nebula]], comparing ultraviolet and visible (top) and infrared (bottom) astronomy. Far more stars are visible in the latter.]]

Webb orbits the Sun near the second [[Lagrange point]] ({{L2|nolink=yes}}) of the Sun–Earth system, which is {{cvt|1500000|km}} farther from the Sun than the Earth's orbit, and about four times farther than the Moon's orbit. Normally an object circling the Sun farther out than Earth would take longer than one year to complete its orbit. But near the {{L2}} point, the combined gravitational pull of the Earth and the Sun allow a spacecraft to orbit the Sun in the same time that it takes the Earth. Staying close to Earth allows data rates to be much faster for a given size of antenna.

The telescope circles about the Sun–Earth {{L2|nolink=yes}} point in a [[halo orbit]], which is inclined with respect to the [[ecliptic]], has a radius varying between about {{cvt|250000|km}} and {{cvt|832000|km}}, and takes about half a year to complete.<ref name="stsci.edu"/> Since {{L2|nolink=yes}} is just an equilibrium point with no gravitational pull, a halo orbit is not an orbit in the usual sense: the spacecraft is actually in orbit around the Sun, and the halo orbit can be thought of as controlled drifting to remain in the vicinity of the {{L2|nolink=yes}} point.<ref>{{cite web|title=Basics of Space Flight|url=http://www2.jpl.nasa.gov/basics/bsf5-1.php|publisher=Jet Propulsion Laboratory|access-date=28 August 2016|archive-date=11 June 2012|archive-url=https://web.archive.org/web/20120611064749/http://www2.jpl.nasa.gov/basics/bsf5-1.php|url-status=live}} {{PD-notice}}</ref> This requires some [[Orbital station-keeping|station-keeping]]: around {{val|2.5|u=m/s}} per year<ref>{{cite web |author=Dichmann |first1=Donald J. |last2=Alberding |first2=Cassandra M. |last3=Yu |first3=Wayne H. |date=5 May 2014 |title=STATIONKEEPING MONTE CARLO SIMULATION FOR THE JAMES WEBB SPACE TELESCOPE |url=https://ntrs.nasa.gov/api/citations/20140007519/downloads/20140007519.pdf |archive-url=https://web.archive.org/web/20211217000634/https://ntrs.nasa.gov/api/citations/20140007519/downloads/20140007519.pdf |archive-date=17 December 2021 |access-date=29 December 2021 |publisher=NASA Goddard Space Flight Center}} {{PD-notice}}</ref> from the total [[Delta-v|∆''v'']] budget of {{val|93|u=m/s}}.<ref>{{cite web |author=Greenhouse |first=Matt |date=1 April 2016 |title=The James Webb Space Telescope Mission |url=https://ntrs.nasa.gov/api/citations/20170004986/downloads/20170004986.pdf |url-status=live |archive-url=https://web.archive.org/web/20211229192654/https://ntrs.nasa.gov/api/citations/20170004986/downloads/20170004986.pdf |archive-date=29 December 2021 |access-date=29 December 2021 |publisher=NASA Goddard Space Flight Center}}</ref>{{rp|p=10}} Two sets of thrusters constitute the observatory's propulsion system.<ref>{{Cite conference |conference=International Symposium on Space Flight Dynamics |last1=Petersen |first1=Jeremy |last2=Tichy |first2=Jason |last3=Wawrzyniak |first3=Geoffrey |last4=Richon |first4=Karen |date=2014-04-21 |title=James Webb Space Telescope Initial Mid-Course Correction Monte Carlo Implementation using Task Parallelism |url=https://ntrs.nasa.gov/citations/20140008868 |url-status=live |archive-url=https://web.archive.org/web/20230609054522/https://ntrs.nasa.gov/citations/20140008868 |archive-date=2023-06-09 |id=GSFC-E-DAA-TN14162 |location=Laurel, MD }}</ref> Because the thrusters are located solely on the Sun-facing side of the observatory, all station-keeping operations are designed to slightly undershoot the required amount of thrust in order to avoid pushing Webb beyond the semi-stable {{L2}} point, a situation which would be unrecoverable. Randy Kimble, the Integration and Test Project Scientist for the JWST, compared the precise station-keeping of Webb to "[[Sisyphus]] [...] rolling this rock up the gentle slope near the top of the hill – we never want it to roll over the crest and get away from him".<ref>{{cite web |last=Kimble |first=Randy |url=https://blogs.nasa.gov/webb/2021/12/27/more-than-you-wanted-to-know-about-webbs-mid-course-corrections/ |title=More Than You Wanted to Know About Webb's Mid-Course Corrections! |work=[[NASA]] |date=27 December 2021 |access-date=27 December 2021 |archive-date=27 December 2021 |archive-url=https://web.archive.org/web/20211227141617/https://blogs.nasa.gov/webb/2021/12/27/more-than-you-wanted-to-know-about-webbs-mid-course-corrections/ |url-status=live }} {{PD-notice}}</ref>
{{multiple image | align =center| direction = horizontal| width =
| header   = Animation of James Webb Space Telescope trajectory
| image1   = Animation of James Webb Space Telescope trajectory - Polar view.gif
| caption1 = Top view
| image2   = Animation of James Webb Space Telescope trajectory - Equatorial view.gif
| caption2 = Side view
| image3   = Animation of James Webb Space Telescope trajectory - Viewed from the Sun.gif
| caption3 = Side view from the Sun
| footer   ={{legend2|magenta|James Webb Space Telescope}}{{·}}{{legend2| RoyalBlue |[[Earth]]}}{{·}}{{legend2| Lime|L2 point}}
}}

=== Infrared astronomy ===
[[File:HUDF-JD2.jpg|thumb|upright=1.4|right|Infrared observations can see objects hidden in visible light, such as the [[HUDF-JD2]] shown here.]]
[[File:Atmospheric Transmission-en.svg|thumb|upright=1.6|right|Atmospheric windows in the infrared: Much of this type of light is blocked when viewed from the Earth's surface. It would be like looking at a rainbow but only seeing one color.]]

Webb is the formal successor to the Hubble Space Telescope (HST), and since its primary emphasis is on [[infrared astronomy]], it is also a successor to the [[Spitzer Space Telescope]]. Webb will far surpass both those telescopes, being able to see many more and much older stars and galaxies.<ref name=RHowardJWST>Howard, Rick, [https://www.nasa.gov/pdf/629955main_RHoward_JWST_3_6_12.pdf "James Webb Space Telescope (JWST)"] {{Webarchive|url=https://web.archive.org/web/20211221150840/https://www.nasa.gov/pdf/629955main_RHoward_JWST_3_6_12.pdf |date=21 December 2021 }}, ''nasa.gov'', 6 March 2012 {{PD-notice}}</ref> Observing in the infrared spectrum is a key technique for achieving this, because of [[cosmological redshift]], and because it better penetrates obscuring dust and gas. This allows observation of dimmer, cooler objects. Since water vapor and carbon dioxide in the Earth's atmosphere strongly absorbs most infrared, ground-based infrared astronomy is limited to narrow wavelength ranges where the atmosphere absorbs less strongly. Additionally, the atmosphere itself radiates in the infrared spectrum, often overwhelming light from the object being observed. This makes a space telescope preferable for infrared observation.<ref>{{cite web|url=http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html|title=Infrared Atmospheric Windows|publisher=Cool Cosmos|access-date=28 August 2016|archive-date=11 October 2018|archive-url=https://web.archive.org/web/20181011101051/http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html|url-status=dead}}</ref>

The more distant an object is, the younger it appears; its light has taken longer to reach human observers. Because the [[Expansion of the universe|universe is expanding]], as the light travels it becomes red-shifted, and objects at extreme distances are therefore easier to see if viewed in the infrared.<ref name="ir_astronomy"/> Webb's infrared capabilities are expected to let it see back in time to the first galaxies forming just a few hundred million years after the Big Bang.<ref name="firstlight">{{cite web|url=http://www.jwst.nasa.gov/firstlight.html|title=Webb Science: The End of the Dark Ages: First Light and Reionization|publisher=NASA|access-date=9 June 2011|archive-date=22 November 2017|archive-url=https://web.archive.org/web/20171122181907/https://jwst.nasa.gov/firstlight.html|url-status=live}} {{PD-notice}}</ref>

Infrared radiation can pass more freely through regions of [[cosmic dust]] that scatter visible light. Observations in infrared allow the study of objects and regions of space which would be obscured by gas and dust in the [[visible spectrum]],<ref name="ir_astronomy">{{cite web|url=http://www.ipac.caltech.edu/Outreach/Edu/importance.html|title=Infrared Astronomy: Overview|publisher=NASA Infrared Astronomy and Processing Center|access-date=30 October 2006|url-status=dead|archive-url=https://web.archive.org/web/20061208151300/http://www.ipac.caltech.edu/Outreach/Edu/importance.html|archive-date=8 December 2006}} {{PD-notice}}</ref> such as the [[molecular cloud]]s where stars are born, the [[circumstellar disks]] that give rise to planets, and the cores of [[active galaxy|active galaxies]].<ref name="ir_astronomy"/>

Relatively cool objects (temperatures less than several thousand degrees) emit their radiation primarily in the infrared, as described by [[Planck's law]]. As a result, most objects that are cooler than stars are better studied in the infrared.<ref name="ir_astronomy"/> This includes the clouds of the [[interstellar medium]], [[brown dwarf]]s, [[planet]]s both in our own and other solar systems, [[comet]]s, and [[Kuiper belt|Kuiper belt objects]] that will be observed with the Mid-Infrared Instrument (MIRI).<ref name=miri/><ref name=firstlight/>

Some of the missions in infrared astronomy that impacted Webb development were [[Spitzer Space Telescope|Spitzer]] and the [[Wilkinson Microwave Anisotropy Probe]] (WMAP).<ref name="ssb-2006">{{cite web |last=Mather |first=John |url=https://jwst.nasa.gov/resources/ssb_2006/mather_sciencesummary.pdf |title=James Webb Space Telescope (JWST) Science Summary for SSB |work=[[NASA]] |date=13 June 2006 |access-date=4 June 2021 |archive-date=27 March 2021 |archive-url=https://web.archive.org/web/20210327214005/https://jwst.nasa.gov/resources/ssb_2006/mather_sciencesummary.pdf |url-status=live }} {{PD-notice}}</ref> Spitzer showed the importance of mid-infrared, which is helpful for tasks such as observing dust disks around stars.<ref name="ssb-2006"/> Also, the WMAP probe showed the universe was "lit up" at redshift 17, further underscoring the importance of the mid-infrared.<ref name="ssb-2006"/> Both these missions were launched in the early 2000s, in time to influence Webb development.<ref name="ssb-2006"/>

== Ground support and operations ==
The [[Space Telescope Science Institute]] (STScI), in [[Baltimore, Maryland]], on the [[Homewood Campus of Johns Hopkins University]], was selected in 2003 as the Science and Operations Center (S&OC) for Webb with an initial budget of US$162.2 million intended to support operations through the first year after launch.<ref>{{cite web|url=https://www.nasa.gov/home/hqnews/2003/jun/HQ_c03r_Webb.html|title=Webb Spacecraft Science & Operations Center Contract Awarded|author1=Savage, Donald|author2=Neal, Nancy|date=6 June 2003|publisher=NASA|access-date=1 February 2017|archive-date=3 January 2022|archive-url=https://web.archive.org/web/20220103132040/https://www.nasa.gov/home/hqnews/2003/jun/HQ_c03r_Webb.html|url-status=live}} {{PD-notice}}</ref> In this capacity, STScI was to be responsible for the scientific operation of the telescope and delivery of data products to the astronomical community. Data was to be transmitted from Webb to the ground via the [[NASA Deep Space Network]], processed and calibrated at STScI, and then distributed online to astronomers worldwide. Similar to how Hubble is operated, anyone, anywhere in the world, will be allowed to submit proposals for observations. Each year several committees of astronomers will [[peer review]] the submitted proposals to select the projects to observe in the coming year. The authors of the chosen proposals will typically have one year of private access to the new observations, after which the data will become publicly available for download by anyone from the online archive at STScI.{{Citation needed|date=September 2022}}

The bandwidth and digital throughput of the satellite is designed to operate at 458 gigabits of data per day for the length of the mission (equivalent to a sustained rate of 5.42 [[Mbps]]).<ref name="wired-20191022"/> Most of the data processing on the telescope is done by conventional single-board computers.<ref>{{cite web|url=http://www.fbodaily.com/archive/2002/10-October/30-Oct-2002/FBO-00195113.htm|title=Single Board Computer|publisher=FBO Daily Issue, FBO #0332|date=30 October 2002|access-date=23 April 2008|archive-date=18 May 2009|archive-url=https://web.archive.org/web/20090518064128/http://www.fbodaily.com/archive/2002/10-October/30-Oct-2002/FBO-00195113.htm|url-status=live}}</ref> The digitization of the analog data from the instruments is performed by the custom SIDECAR ASIC (System for Image Digitization, Enhancement, Control And Retrieval [[Application-specific integrated circuit|Application Specific Integrated Circuit]]). NASA stated that the SIDECAR ASIC will include all the functions of a {{cvt|9.1|kg}} instrument box in a {{cvt|3|cm}} package and consume only 11&nbsp;milliwatts of power.<ref name="Sidecar">{{cite web|url=http://www.nasa.gov/topics/universe/features/jwst_digital.html|title=Amazing Miniaturized 'SIDECAR' Drives Webb Telescope's Signal|date=20 February 2008|publisher=NASA|access-date=22 February 2008|archive-date=27 February 2008|archive-url=https://web.archive.org/web/20080227160340/http://www.nasa.gov/topics/universe/features/jwst_digital.html|url-status=live}} {{PD-notice}}</ref> Since this conversion must be done close to the detectors, on the cold side of the telescope, the low power dissipation is crucial for maintaining the low temperature required for optimal operation of Webb.<ref name="Sidecar"/>

The telescope is equipped with a [[solid-state drive]] (SSD) with a capacity of 68&nbsp;GB, used as temporary storage for data collected from its scientific instruments. By the end of the 10-year mission, the usable capacity of the drive is expected to decrease to 60&nbsp;GB due to the effects of radiation and read/write operations.<ref>{{cite journal |last1=Hecht |first1=Jeff |last2=Potter |first2=Ned |last3=Koziol |first3=Michael |year=2022 |title=Inside the Universe Machine |journal=IEEE Spectrum |volume=59 |issue=9 |page=48|doi=10.1109/MSPEC.2022.9881257 |s2cid=252112744 }}</ref>

=== Micrometeoroid strikes ===
The C3{{efn|name= c3Position |The C3 mirror segment is positioned in the outer ring of segments, located at the '5 o'clock' number of a [[clock face]], when viewing the primary mirror face-on.<ref name= c3Segment >{{cite web |last=Sutherland |first=Scott |url=https://www.theweathernetwork.com/ca/news/article/james-webb-space-telescope-mirror-segment-hit-by-micrometeoroid |title=Webb's primary mirror was just hit by a meteoroid, but it was built to endure |website=The Weather Network |date=10 June 2022 |access-date=10 June 2022 |archive-date=9 June 2022 |archive-url=https://web.archive.org/web/20220609191423/https://www.theweathernetwork.com/ca/news/article/james-webb-space-telescope-mirror-segment-hit-by-micrometeoroid |url-status=live }}</ref>}} mirror segment suffered a [[micrometeoroid]] strike from a large dust mote-sized particle between 23 and 25 May 2022, the fifth and largest strike since launch, reported 8 June 2022, which required engineers to compensate for the strike using a [[mirror actuator]].<ref name= wHarwood >{{cite web |last=Harwood |first=William |url=https://www.cbsnews.com/news/webb-telescope-micrometeoroid-impact-mirror-segment/ |title=Webb telescope still performing well after micrometeoroid impact on mirror segment, NASA says |website=CBS News |date=9 June 2022 |access-date=10 June 2022 |archive-date=9 June 2022 |archive-url=https://web.archive.org/web/20220609203112/https://www.cbsnews.com/news/webb-telescope-micrometeoroid-impact-mirror-segment/ |url-status=live }}</ref> Despite the strike, a NASA characterization report states "all JWST observing modes have been reviewed and confirmed to be ready for science use" as of 10 July 2022.{{refn|name="Howell 2022-07-18"|Howell, Elizabeth [https://www.space.com/james-webb-space-telescope-micrometeoroid-damage (18 July 2022) James Webb Space Telescope picture shows noticeable damage from micrometeoroid strike] cites a NASA-ESA-CSA joint report (12 July 2022) by 611 co-authors from 44 institutions.<ref name="Rigby 2022-07-12"/>{{rp|p=2}}}} Micrometeoroids strike Webb an average of once or twice per month, and only the May 2022 strike caused noticeable damage.<ref>{{cite web | url=https://www.space.com/james-webb-space-telescope-micrometeoroid-environment | title=The James Webb Space Telescope gets its own micrometeoroid forecast — here's how | website=[[Space.com]] | date=2 February 2023 }}</ref> After that strike, mission personnel implemented a strategy to change Webb's observations to reduce the risk of further damage. The strategy is to avoid pointing the mirror toward "micrometeoroid avoidance zones" at particular points along Webb's orbit.<ref>{{cite web | url=https://www.space.com/james-webb-space-telescope-micrometeoroid-observing-strategy | title=James Webb Space Telescope tweaks observing plans to avoid micrometeoroids | website=[[Space.com]] | date=16 November 2022 }}</ref>

== From launch through commissioning ==
{{Main|Launch and commissioning of the James Webb Space Telescope}}

=== Launch ===
{{Main|Ariane flight VA256}}
The launch (designated [[Ariane flight VA256]]) took place as scheduled at 12:20 UTC on 25 December 2021 on an [[Ariane 5]] rocket that lifted off from the [[Guiana Space Centre]] in [[French Guiana]].<ref name="AS-20211225" /><ref name="NASA-20211227">{{cite news |last1=Pinoi |first1=Natasha |last2=Fiser |first2=Alise |last3=Betz |first3=Laura |title=NASA's Webb Telescope Launches to See First Galaxies, Distant Worlds – NASA's James Webb Space Telescope launched at 7:20 a.m. EST Saturday [Dec. 25, 2021] on an Ariane 5 rocket French Guiana, South America |url=https://www.nasa.gov/press-release/nasas-webb-telescope-launches-to-see-first-galaxies-distant-worlds |date=27 December 2021 |work=[[NASA]] |access-date=28 December 2021 |archive-date=12 April 2022 |archive-url=https://web.archive.org/web/20220412131658/https://www.nasa.gov/press-release/nasas-webb-telescope-launches-to-see-first-galaxies-distant-worlds/ |url-status=live }}</ref> The telescope was confirmed to be receiving power, starting a two-week deployment phase of its parts<ref name="Space Explored 2021">{{cite web | title=How to track James Webb Space Telescope, mission timeline | website=Space Explored | date=31 December 2021 | url=https://spaceexplored.com/2021/12/30/how-to-track-james-webb-space-telescope-mission-timeline/ | access-date=1 January 2022 | archive-date=1 January 2022 | archive-url=https://web.archive.org/web/20220101084226/https://spaceexplored.com/2021/12/30/how-to-track-james-webb-space-telescope-mission-timeline/ | url-status=live }}</ref> and traveling to its target destination.<ref name="WP-20211225">{{cite news |last=Achenbach |first=Joel |title=NASA's James Webb Space Telescope launches in French Guiana – $10 billion successor to Hubble telescope will capture light from first stars and study distant worlds |url=https://www.washingtonpost.com/science/2021/12/25/webb-space-telescope-launch/ |date=25 December 2021 |newspaper=[[The Washington Post]] |access-date=25 December 2021 |archive-date=25 December 2021 |archive-url=https://web.archive.org/web/20211225125938/https://www.washingtonpost.com/science/2021/12/25/webb-space-telescope-launch/ |url-status=live }}</ref><ref name="NYT-20211225">{{cite news |title=Live Updates: Webb Telescope Launches on Long-Awaited Journey |url=https://www.nytimes.com/live/2021/12/25/science/webb-telescope-launch-nasa |date=25 December 2021 |work=[[The New York Times]] |access-date=25 December 2021 |archive-date=25 December 2021 |archive-url=https://web.archive.org/web/20211225104032/https://www.nytimes.com/live/2021/12/25/science/webb-telescope-launch-nasa |url-status=live }}</ref><ref name="NYT-20211225do">{{cite news |last1=Overbye |first1=Dennis |last2=Roulette |first2=Joey |title=James Webb Space Telescope Launches on Journey to See the Dawn of Starlight – Astronomers were jubilant as the spacecraft made it off the launchpad, following decades of delays and cost overruns. The Webb is set to offer a new keyhole into the earliest moments of our universe. |url=https://www.nytimes.com/2021/12/25/science/james-webb-telescope-launch.html |date=25 December 2021 |work=[[The New York Times]] |access-date=25 December 2021 |archive-date=29 December 2021 |archive-url=https://web.archive.org/web/20211229103315/https://www.nytimes.com/2021/12/25/science/james-webb-telescope-launch.html |url-status=live }}</ref> The telescope was released from the upper stage 27 minutes 7 seconds after launch, beginning a 30-day adjustment to place the telescope in a [[Lissajous orbit]]<ref>{{cite web|url=https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100108651|access-date=2022-02-05|title=Lissajous orbit|website=Oxford Reference|archive-date=5 February 2022|archive-url=https://web.archive.org/web/20220205001239/https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100108651|url-status=live}}</ref> around the [[Lagrange point#L2 point|L2]] [[Lagrange point]].

The telescope was launched with slightly less speed than needed to reach its final orbit, and slowed down as it travelled away from Earth, in order to reach L<sub>2</sub> with only the velocity needed to enter its orbit there. The telescope reached L<sub>2</sub> on 24 January 2022. The flight included three planned course corrections to adjust its speed and direction. This is because the observatory could recover from underthrust (going too slowly), but could not recover from overthrust (going too fast)&nbsp;– to protect highly temperature-sensitive instruments, the sunshield must remain between telescope and Sun, so the spacecraft could not turn around or use its thrusters to slow down.<ref>{{cite web|url=https://blogs.nasa.gov/webb/|title=James Webb Space Telescope|website=blogs.nasa.gov|access-date=22 November 2021|archive-date=18 November 2021|archive-url=https://web.archive.org/web/20211118051619/https://blogs.nasa.gov/webb/|url-status=live}}</ref>

An {{L2}} orbit is [[Stability theory|unstable]], so JWST needs to use propellant to maintain its halo orbit around L2 (known as [[Orbital station-keeping|station-keeping]]) to prevent the telescope from drifting away from its orbital position.<ref>{{cite web |title=JWST Orbit |url=https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-orbit |url-status=live |archive-url=https://web.archive.org/web/20220711230845/https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-orbit |archive-date=11 July 2022 |access-date=10 July 2022 |publisher=James Webb Space Telescope User Documentation}}</ref> It was designed to carry enough propellant for 10 years,<ref name="HowLong">{{citation-attribution|{{cite web |date=2017 |title=Frequently asked questions: How long will the Webb mission last? |url=http://jwst.nasa.gov/faq.html#howlong |url-status=live |archive-url=https://web.archive.org/web/20190616111934/https://jwst.nasa.gov/faq.html#howlong |archive-date=16 June 2019 |access-date=29 June 2015 |publisher=NASA James Webb Space Telescope}}}}</ref> but the precision of the Ariane 5 launch and the first midcourse correction were credited with saving enough onboard fuel that JWST may be able to maintain its orbit for around 20 years instead.<ref name="Fuelsave">{{cite web |last1=Fox |first1=Karen |title=NASA Says Webb's Excess Fuel Likely to Extend its Lifetime Expectations |url=https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-excess-fuel-likely-to-extend-its-lifetime-expectations/ |url-status=live |archive-url=https://web.archive.org/web/20220106191652/https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-excess-fuel-likely-to-extend-its-lifetime-expectations/ |archive-date=6 January 2022 |access-date=30 December 2021 |website=James Webb Space Telescope (NASA Blogs)|date=29 December 2021 }}</ref><ref name="Ars1">{{cite web |last=Berger |first=Eric |date=10 January 2022 |title=All hail the Ariane 5 rocket, which doubled the Webb telescope's lifetime |url=https://arstechnica.com/science/2022/01/all-hail-the-ariane-5-rocket-which-doubled-the-webb-telescopes-lifetime/ |url-status=live |archive-url=https://web.archive.org/web/20220110230832/https://arstechnica.com/science/2022/01/all-hail-the-ariane-5-rocket-which-doubled-the-webb-telescopes-lifetime/ |archive-date=10 January 2022 |access-date=11 January 2022 |website=www.arstechnica.com |publisher=Ars Technica}}</ref><ref name="BBC1">{{cite web |last=Amos |first=Jonathan |date=9 January 2022 |title=James Webb telescope completes epic deployment sequence |url=https://www.bbc.com/news/science-environment-59914936 |url-status=live |archive-url=https://web.archive.org/web/20220110064805/https://www.bbc.com/news/science-environment-59914936 |archive-date=10 January 2022 |access-date=10 January 2022 |website=www.bbc.com |publisher=BBC News}}</ref> [[Space.com]] called the launch "flawless".<ref name="reaction2">{{cite web |author1=Pultarova |first=Tereza |date=25 December 2021 |title='It's truly Christmas': James Webb Space Telescope's yuletide launch has NASA overjoyed |url=https://www.space.com/james-webb-space-telescope-launch-nasa-reaction |url-status=live |archive-url=https://web.archive.org/web/20220104054403/https://www.space.com/james-webb-space-telescope-launch-nasa-reaction |archive-date=4 January 2022 |access-date=4 January 2022 |website=Space.com}}</ref><gallery mode="packed" heights="180px">
File:JWST launch configuration.png|alt=JWST launch configuration|Diagram of Webb inside Ariane 5
File:Ariane 5 with James Webb Space Telescope Prelaunch (NHQ202112230012).jpg|alt=JWST and Ariane 5 Rollout|Ariane 5 and Webb at the [[ELA-3]] launch pad
File:James Webb Space Telescope Launch (NHQ202112250010).jpg|alt=Ariane 5 containing the James Webb Space Telescope lifting-off from the launch pad|Ariane 5 containing the James Webb Space Telescope lifting-off from the launch pad
File:James Webb Space Telescope Launch.jpg|alt=Ariane 5 moments after lift-off|Ariane 5 containing Webb moments after lift-off
File:JWST as seen from the ESC-D Cryotechnic upper stage.png|alt=JWST as seen from the ESC-D Cryotechnic upper stage|Webb as seen from the [[Ariane 5#Second stage|ESC-D Cryotechnic upper stage]] shortly after separation, approximately 29 minutes after launch. Part of the Earth with the [[Gulf of Aden]] is visible in the background of the image.<ref name=jwstSeparation>Camera on ESC-D Cryotechnic upper stage [https://www.youtube.com/watch?v=7nT7JGZMbtM&t=6637s (25 Dec 2021) view of newly separated JWST, as seen from the ESC-D Cryotechnic upper stage] {{Webarchive|url=https://web.archive.org/web/20211225214400/https://www.youtube.com/watch?v=7nT7JGZMbtM&t=6637s |date=25 December 2021 }}</ref>
</gallery>

=== Transit and structural deployment ===
[[File:JWSTDeployment.jpg|thumb|upright=2|Structural deployment timeline<ref name=howBig/>]]
Webb was released from the rocket upper stage 27 minutes after a flawless launch.<ref name="AS-20211225">{{cite press release |url=https://www.arianespace.com/press-release/ariane-5-successful-launch-webb-space-telescope/ |title=Ariane 5 goes down in history with successful launch of Webb |work=[[Arianespace]] |date=25 December 2021 |access-date=25 December 2021 |archive-date=10 March 2022 |archive-url=https://web.archive.org/web/20220310095539/https://www.arianespace.com/press-release/ariane-5-successful-launch-webb-space-telescope/ |url-status=live }}</ref><ref name="reaction2"/> Starting 31 minutes after launch, and continuing for about 13 days, Webb began the process of deploying its solar array, antenna, sunshield, and mirrors.<ref name=":1">{{Citation|title=James Webb Space Telescope Deployment Sequence (Nominal)| date=12 November 2021 |url=https://www.youtube.com/watch?v=RzGLKQ7_KZQ |archive-url=https://ghostarchive.org/varchive/RzGLKQ7_KZQ|archive-date=23 December 2021|url-status=live|pages=1:47|access-date=23 December 2021}}{{cbignore}}</ref> Nearly all deployment actions are commanded by the Space Telescope Science Institute in [[Baltimore]], Maryland, except for two early automatic steps, solar panel unfolding and communication antenna deployment.<ref>{{cite web |last1=Warren |first1=Haygen |title=James Webb Space Telescope en route to L2; deployment sequence underway |url=https://www.nasaspaceflight.com/2021/12/james-webb-deployment-sequence-underway/ |website=NASA spaceflight.com |access-date=5 January 2022 |date=27 December 2021 |archive-date=5 January 2022 |archive-url=https://web.archive.org/web/20220105013628/https://www.nasaspaceflight.com/2021/12/james-webb-deployment-sequence-underway/ |url-status=live }}</ref><ref>{{cite news |last1=Achenbach |first1=Joel |title=NASA thrilled: Webb Space Telescope deploys sun shield, evades many potential 'single-point failures' |url=https://www.washingtonpost.com/science/2022/01/04/webb-telescope-sun-shield-deployed/ |newspaper=The Washington Post |access-date=5 January 2022 |date=4 January 2022 |archive-date=4 January 2022 |archive-url=https://web.archive.org/web/20220104233214/https://www.washingtonpost.com/science/2022/01/04/webb-telescope-sun-shield-deployed/ |url-status=live }}</ref> The mission was designed to give ground controllers flexibility to change or modify the deployment sequence in case of problems.<ref name="ExploreDeploy">{{cite web |title=Gimbaled Antenna Assembly |url=https://webb.nasa.gov/content/webbLaunch/deploymentExplorer.html |url-status=live |archive-url=https://web.archive.org/web/20220127113812/https://webb.nasa.gov/content/webbLaunch/deploymentExplorer.html |archive-date=27 January 2022 |access-date=27 December 2021 |website=James Webb Space Telescope |publisher=NASA}}</ref>

[[File:James-Webb-Space-Telescope-Deployment-Sequence- Nominal.webm|thumb|Structural deployment sequence]]
At 7:50{{nbsp}}p.m. EST on 25 December 2021, about 12 hours after launch, the telescope's pair of primary rockets began firing for 65 minutes to make the first of three planned mid-course corrections.<ref>{{cite web |last1=Fox |first1=Karen |title=The First Mid-Course Correction Burn |url=https://blogs.nasa.gov/webb/2021/12/25/the-first-mid-course-correction-burn/ |website=NASA Blogs |date=25 December 2021 |access-date=27 December 2021 |archive-date=26 December 2021 |archive-url=https://web.archive.org/web/20211226224905/https://blogs.nasa.gov/webb/2021/12/25/the-first-mid-course-correction-burn/ |url-status=live }}</ref> On day two, the high gain communication antenna deployed automatically.<ref name="ExploreDeploy" />

On 27 December 2021, at 60 hours after launch, Webb's rockets fired for nine minutes and 27 seconds to make the second of three mid-course corrections for the telescope to arrive at its L<sub>2</sub> destination.<ref>{{cite web |last1=Fox |first1=Karen |title=Webb's Second Mid-Course Correction Burn |url=https://blogs.nasa.gov/webb/2021/12/27/webbs-second-mid-course-correction-burn/ |website=James Webb Space Telescope (NASA Blogs) |date=27 December 2021 |access-date=29 December 2021 |archive-date=29 December 2021 |archive-url=https://web.archive.org/web/20211229005346/https://blogs.nasa.gov/webb/2021/12/27/webbs-second-mid-course-correction-burn/ |url-status=live }}</ref> On 28 December 2021, three days after launch, mission controllers began the multi-day deployment of Webb's all-important sunshield. On 30 December 2021, controllers successfully completed two more steps in unpacking the observatory. First, commands deployed the aft "momentum flap", a device that provides balance against solar pressure on the sunshield, saving fuel by reducing the need for thruster firing to maintain Webb's orientation.<ref>{{cite web |last=Fisher |first=Alise |date=30 December 2021 |title=Webb's Aft Momentum Flap Deployed |url=https://blogs.nasa.gov/webb/2021/12/30/webbs-aft-momentum-flap-deployed/ |website=James Webb Space Telescope (NASA Blogs) |access-date=31 December 2021 |archive-date=30 December 2021 |archive-url=https://web.archive.org/web/20211230221838/https://blogs.nasa.gov/webb/2021/12/30/webbs-aft-momentum-flap-deployed/ |url-status=live }}</ref>

On 31 December 2021, the ground team extended the two telescoping "mid booms" from the left and right sides of the observatory.<ref name="Twobooms">{{cite web |last1=Lynch |first1=Patrick |title=With Webb's Mid-Booms Extended, Sunshield Takes Shape |url=https://blogs.nasa.gov/webb/2021/12/31/with-webbs-mid-booms-extended-sunshield-takes-shape/ |website=James Webb Space Telescope (NASA Blogs) |access-date=1 January 2022 |date=31 December 2021 |archive-date=24 May 2022 |archive-url=https://web.archive.org/web/20220524194046/https://blogs.nasa.gov/webb/2021/12/31/with-webbs-mid-booms-extended-sunshield-takes-shape/ |url-status=live }}</ref> The left side deployed in 3 hours and 19 minutes; the right side took 3 hours and 42 minutes.<ref name="Firstboom">{{cite web |last1=Lynch |first1=Patrick |date=31 December 2021 |title=First of Two Sunshield Mid-Booms Deploys |url=https://blogs.nasa.gov/webb/2021/12/31/first-of-two-sunshield-mid-booms-deploys/ |url-status=live |archive-url=https://web.archive.org/web/20220429111850/https://blogs.nasa.gov/webb/2021/12/31/first-of-two-sunshield-mid-booms-deploys/ |archive-date=29 April 2022 |access-date=1 January 2022 |website=James Webb Space Telescope (NASA Blogs)}}</ref><ref name="Twobooms" /> Commands to separate and tension the membranes followed between 3 and 4 January and were successful.<ref name="Twobooms" /> On 5 January 2022, mission control successfully deployed the telescope's secondary mirror, which locked itself into place to a tolerance of about one and a half millimeters.<ref>{{cite web |last=Fisher |first=Alise |date=5 January 2022 |title=Secondary Mirror Deployment Confirmed |url=https://blogs.nasa.gov/webb/2022/01/05/secondary-mirror-deployment-confirmed/ |website=James Webb Space Telescope (NASA Blogs) |access-date=6 January 2022 |archive-date=5 January 2022 |archive-url=https://web.archive.org/web/20220105225237/https://blogs.nasa.gov/webb/2022/01/05/secondary-mirror-deployment-confirmed/ |url-status=live }}</ref>

The last step of structural deployment was to unfold the wings of the primary mirror. Each panel consists of three primary mirror segments and had to be folded to allow the space telescope to be installed in the [[Payload fairing|fairing]] of the Ariane rocket for the launch of the telescope. On 7 January 2022, NASA deployed and locked in place the port-side wing,<ref name="NASA_2022_01_07">{{cite web |last=Fisher |first=Alise |date=7 January 2022 |title=First of Two Primary Mirror Wings Unfolds |website=James Webb Space Telescope (NASA Blogs) |access-date=8 January 2022 |url=https://blogs.nasa.gov/webb/2022/01/07/first-of-two-primary-mirror-wings-unfolds/ |archive-date=7 January 2022 |archive-url=https://web.archive.org/web/20220107230121/https://blogs.nasa.gov/webb/2022/01/07/first-of-two-primary-mirror-wings-unfolds/ |url-status=live }}</ref> and on 8 January, the starboard-side mirror wing. This successfully completed the structural deployment of the observatory.<ref>{{cite web|url=https://blogs.nasa.gov/webb/2022/01/08/primary-mirror-wings-deployed-all-major-deployments-complete/|title=Primary Mirror Wings Deployed, All Major Deployments Complete|last=Fisher|first=Alise|date=8 January 2022|website=James Webb Space Telescope (NASA Blogs)|access-date=8 January 2022|archive-date=23 January 2022|archive-url=https://web.archive.org/web/20220123110611/https://blogs.nasa.gov/webb/2022/01/08/primary-mirror-wings-deployed-all-major-deployments-complete/|url-status=live}}</ref><ref>{{cite web |last1=Berger |first1=Eric |title=Remarkably, NASA has completed deployment of the Webb space telescope |url=https://cansciencenews.com/2022/01/08/remarkably-nasa-has-completed-deployment-of-the-webb-space-telescope/ |website=cansciencenews.com |access-date=8 January 2022 |date=8 January 2022 |archive-date=9 January 2022 |archive-url=https://web.archive.org/web/20220109071434/https://cansciencenews.com/2022/01/08/remarkably-nasa-has-completed-deployment-of-the-webb-space-telescope/ |url-status=live }}</ref><ref>{{cite web |title=Space telescope's 'golden eye' opens, last major hurdle |url=https://phys.org/news/2022-01-space-telescope-golden-eye-major.html |website=phys.org |access-date=9 January 2022 |date=8 January 2022 |archive-date=8 January 2022 |archive-url=https://web.archive.org/web/20220108210342/https://phys.org/news/2022-01-space-telescope-golden-eye-major.html |url-status=live }}</ref>

On 24 January 2022, at 2:00{{nbsp}}p.m. Eastern Standard Time,<ref name="Webb blog 2022-01-21">{{cite web |last=Fisher |first=Alise |date=21 January 2022 |title=Webb's Journey to L2 Is Nearly Complete |url=https://blogs.nasa.gov/webb/2022/01/21/webbs-journey-to-l2-is-nearly-complete |access-date=25 January 2022 |website=James Webb Space Telescope (NASA Blogs) |archive-date=25 January 2022 |archive-url=https://web.archive.org/web/20220125000731/https://blogs.nasa.gov/webb/2022/01/21/webbs-journey-to-l2-is-nearly-complete/ |url-status=live }}</ref> nearly a month after launch, a third and final course correction took place, inserting Webb into its planned [[halo orbit]] around the Sun–Earth L<sub>2</sub> point.<ref name="NYT-20220124">{{cite news |last=Roulette |first=Joey |title=After Million-Mile Journey, James Webb Telescope Reaches Destination – The telescope's safe arrival is a relief to scientists who plan to spend the next 10 or more years using it to study ancient galaxies.|url=https://www.nytimes.com/2022/01/24/science/james-webb-telescope-arrival.html |archive-url=https://web.archive.org/web/20220124191053/https://www.nytimes.com/2022/01/24/science/james-webb-telescope-arrival.html |archive-date=2022-01-24 |url-access=subscription |url-status=live |date=24 January 2022 |newspaper=[[The New York Times]] |access-date=24 January 2022 }}</ref><ref name="NASA-20220124">{{cite web|url=https://blogs.nasa.gov/webb/2022/01/24/orbital-insertion-burn-a-success-webb-arrives-at-l2/|title=Orbital Insertion Burn a Success, Webb Arrives at L2 – James Webb Space Telescope|website=Blogs.nasa.gov|date=24 January 2022 |access-date=12 February 2022|archive-date=12 February 2022|archive-url=https://web.archive.org/web/20220212041650/https://blogs.nasa.gov/webb/2022/01/24/orbital-insertion-burn-a-success-webb-arrives-at-l2/|url-status=live}}</ref>

The MIRI instrument has four observing modes&nbsp;– imaging, low-resolution spectroscopy, medium-resolution spectroscopy and coronagraphic imaging. "On Aug. 24, a mechanism that supports medium-resolution spectroscopy (MRS), exhibited what appears to be increased friction during setup for a science observation. This mechanism is a grating wheel that allows scientists to select between short, medium, and longer wavelengths when making observations using the MRS mode", said NASA in a press statement.<ref>{{Cite web |date=2022-09-21 |title=James Webb Space Telescope runs into technical issue |url=https://indianexpress.com/article/technology/science/james-webb-space-telescope-runs-into-technical-issue-8163593/ |access-date=2022-09-28 |website=The Indian Express |language=en |archive-date=28 September 2022 |archive-url=https://web.archive.org/web/20220928094528/https://indianexpress.com/article/technology/science/james-webb-space-telescope-runs-into-technical-issue-8163593/ |url-status=live }}</ref>

[[File:Animation Of Webb's Orbit.webm|thumb|Animation of Webb's halo orbit]]

===Commissioning and testing===
On 12 January 2022, while still in transit, mirror alignment began. The primary mirror segments and secondary mirror were moved away from their protective launch positions. This took about 10 days, because the 132<ref name="Webb blog 2022-01-19">{{cite web|url=https://blogs.nasa.gov/webb/2022/01/19/webb-mirror-segment-deployments-complete|title=Webb Mirror Segment Deployments Complete – James Webb Space Telescope|date=19 January 2022 |access-date=24 January 2022|archive-date=24 January 2022|archive-url=https://web.archive.org/web/20220124072108/https://blogs.nasa.gov/webb/2022/01/19/webb-mirror-segment-deployments-complete/|url-status=live}}</ref> [[actuator]] motors are designed to fine-tune the mirror positions at microscopic accuracy (10 [[nanometer]] increments) and must each move over 1.2 million increments (12.5&nbsp;mm) during initial alignment.<ref name="Webb blog 2022-01-12">{{cite web|url=https://blogs.nasa.gov/webb/2022/01/12/webb-begins-its-months-long-mirror-alignment|title=Webb Begins Its Months-Long Mirror Alignment – James Webb Space Telescope|date=12 January 2022 |access-date=17 January 2022|archive-date=16 January 2022|archive-url=https://web.archive.org/web/20220116205042/https://blogs.nasa.gov/webb/2022/01/12/webb-begins-its-months-long-mirror-alignment/|url-status=live}}</ref><ref name="Webb blog 2022-01-13">{{cite web|url=https://blogs.nasa.gov/webb/2022/01/13/mirror-mirroron-its-way/|title=Mirror, Mirror...On Its Way! – James Webb Space Telescope|website=Blogs.nasa.gov|date=13 January 2022 |access-date=12 February 2022|archive-date=27 January 2022|archive-url=https://web.archive.org/web/20220127230933/https://blogs.nasa.gov/webb/2022/01/13/mirror-mirroron-its-way/|url-status=live}}</ref>

Mirror alignment requires each of the 18 mirror segments, and the secondary mirror, to be positioned to within 50 nanometers. NASA compares the required accuracy by analogy: "If the Webb primary mirror were the size of the United States, each [mirror] segment would be the size of Texas, and the team would need to line the height of those Texas-sized segments up with each other to an accuracy of about 1.5 inches".<ref name="Webb blog 2022-02-03">{{cite web|url=https://blogs.nasa.gov/webb/2022/02/03/photons-incoming-webb-team-begins-aligning-the-telescope|title=Photons Incoming: Webb Team Begins Aligning the Telescope – James Webb Space Telescope|date=3 February 2022 |access-date=5 February 2022|archive-date=30 April 2022|archive-url=https://web.archive.org/web/20220430083322/https://blogs.nasa.gov/webb/2022/02/03/photons-incoming-webb-team-begins-aligning-the-telescope/|url-status=live}} {{PD-notice}}</ref>

<gallery caption="James Webb Space Telescope Mirror alignment animations" mode="packed" heights="150">
File:JWST Segment Image Identification.gif|Segment image identification. 18 mirror segments are moved to determine which segment creates which segment image. After matching the mirror segments to their respective images, the mirrors are tilted to bring all the images near a common point for further analysis.
File:JWST Segment Alignment.gif|Segment alignment begins by defocusing the segment images by moving the secondary mirror slightly. Mathematical analysis, called phase retrieval, is applied to the defocused images to determine the precise positioning errors of the segments. Adjustments of the segments then result in 18 well-corrected "telescopes". However, the segments still do not work together as a single mirror.
File:JWST Image Stacking.gif|Image stacking. To put all of the light in a single place, each segment image must be stacked on top of one another. In the image stacking step, the individual segment images are moved so that they fall precisely at the center of the field to produce one unified image. This process prepares the telescope for coarse phasing.
File:JWST Telescope Alignment Over Instrument Fields of View.gif|Telescope alignment over instrument fields of view. After fine phasing, the telescope is well aligned at one place in the NIRCam field of view. Next the alignment must be extended to the rest of the instruments.
</gallery>

Mirror alignment was a complex operation split into seven phases, that had been repeatedly rehearsed using a 1:6 scale model of the telescope.<ref name="Webb blog 2022-02-03" /> Once the mirrors reached {{cvt|120|K|0}},<ref name="Webb blog 2022-01-31">{{cite web|url=https://blogs.nasa.gov/webb/2022/01/31/following-webbs-arrival-at-l2-telescope-commissioning-set-to-begin/|title=Following Webb's Arrival at L2, Telescope Commissioning Set to Begin – James Webb Space Telescope|date=31 January 2022 |access-date=5 February 2022|archive-date=5 February 2022|archive-url=https://web.archive.org/web/20220205043153/https://blogs.nasa.gov/webb/2022/01/31/following-webbs-arrival-at-l2-telescope-commissioning-set-to-begin/|url-status=live}}</ref> [[NIRCam]] targeted the 7th-magnitude star HD 84406 in [[Ursa Major]].{{efn|HD 84406 is a star approximately 258.5 [[light-year]]s away in the [[constellation]] of [[Ursa Major]]. The star is a [[spectral type]] [[G star]] and has a high [[proper motion]].<ref name="SIMBAD">{{cite simbad |title=HD 84406 |access-date=2022-01-25}}</ref>}}<ref name="GZM-20220204">{{cite news |last=Dvorsky |first=George |date=4 February 2022 |title=Webb Space Telescope Successfully Sees Its First Glimmer of Light – HD 84406 will go down in history as the first star spotted by the $10 billion space telescope. |work=[[Gizmodo]] |url=https://gizmodo.com/james-webb-space-telescop-first-star-light-hd-84406-1848480785 |url-status=live |access-date=4 February 2022 |archive-url=https://web.archive.org/web/20220224094756/https://gizmodo.com/james-webb-space-telescop-first-star-light-hd-84406-1848480785 |archive-date=24 February 2022}}</ref><ref name="FT-20220206">{{cite news |last=Hood |first=Abby Lee |date=6 February 2022 |title=The James Webb Space Telescope Just Detected Its First Signal – We're Watching The Future Unfold In Real Time |work=Futurism.com |url=https://futurism.com/the-byte/james-webb-telescope-first-signal |url-status=live |access-date=6 February 2022 |archive-url=https://web.archive.org/web/20220319005008/https://futurism.com/the-byte/james-webb-telescope-first-signal |archive-date=19 March 2022}}</ref> To do this, NIRCam took 1560 images of the sky and used these wide-ranging images to determine where in the sky each segment of the main mirror initially pointed.<ref name="Webb blog 2022-02-11" /> At first, the individual primary mirror segments were greatly misaligned, so the image contained 18 separate, blurry, images of the star field, each containing an image of the target star. The 18 images of HD 84406 are matched to their respective mirror segments, and the 18 segments are brought into approximate alignment centered on the star ("Segment Image Identification"). Each segment was then individually corrected of its major focusing errors, using a technique called [[phase retrieval]], resulting in 18 separate good quality images from the 18 mirror segments ("Segment Alignment"). The 18 images from each segment, were then moved so they precisely overlap to create a single image ("Image Stacking").<ref name="Webb blog 2022-02-03" />

With the mirrors positioned for almost correct images, they had to be fine tuned to their operational accuracy of 50 nanometers, less than one [[wavelength]] of the light that will be detected. A technique called ''dispersed fringe sensing'' was used to compare images from 20 pairings of mirrors, allowing most of the errors to be corrected ("Coarse Phasing"), and then introduced light defocus to each segment's image, allowing detection and correction of almost all remaining errors ("Fine Phasing"). These two processes were repeated three times, and Fine Phasing will be routinely checked throughout the telescope's operation. After three rounds of Coarse and Fine Phasing, the telescope was well aligned at one place in the NIRCam field of view. Measurements will be made at various points in the captured image, across all instruments, and corrections calculated from the detected variations in intensity, giving a well-aligned outcome across all instruments ("Telescope Alignment Over Instrument Fields of View"). Finally, a last round of Fine Phasing and checks of image quality on all instruments was performed, to ensure that any small residual errors remaining from the previous steps, were corrected ("Iterate Alignment for Final Correction"). The telescope's mirror segments were then aligned and able to capture precise focused images.<ref name="Webb blog 2022-02-03" />

In preparation for alignment, NASA announced at 19:28 UTC on 3 February 2022, that NIRCam had detected the telescope's first [[photon]]s (although not yet complete images).<ref name="Webb blog 2022-02-03" /><ref name="first photons">{{cite web|url=https://mobile.twitter.com/NASAWebb/status/1489319970324496386|title=Our NIRCam instrument's detectors saw their 1st photons of starlight! While #NASAWebb is not yet ready for science, this is the first of many steps to capture images that are at first unfocused, used to slowly fine-tune the optics|website=Twitter.com|access-date=12 February 2022|archive-date=8 February 2022|archive-url=https://web.archive.org/web/20220208224751/https://mobile.twitter.com/nasawebb/status/1489319970324496386|url-status=live}}</ref> On 11 February 2022, NASA announced the telescope had almost completed phase 1 of alignment, with every segment of its primary mirror having located and imaged the target star HD 84406, and all segments brought into approximate alignment.<ref name="Webb blog 2022-02-11">{{cite web |title=Photons Received: Webb Sees Its First Star – 18 Times – James Webb Space Telescope |url=https://blogs.nasa.gov/webb/2022/02/11/photons-received-webb-sees-its-first-star-18-times/ |url-status=live |archive-url=https://web.archive.org/web/20220211235906/https://blogs.nasa.gov/webb/2022/02/11/photons-received-webb-sees-its-first-star-18-times/ |archive-date=11 February 2022 |access-date=12 February 2022 |website=Blogs.nasa.gov|date=11 February 2022 }}</ref> Phase 1 alignment was completed on 18 February 2022,<ref name="Webb blog 2022-02-18">{{cite web|url=https://blogs.nasa.gov/webb/2022/02/18/webb-team-brings-18-dots-of-starlight-into-hexagonal-formation/|title=Webb Team Brings 18 Dots of Starlight Into Hexagonal Formation|website=Blogs.nasa.gov|date=18 February 2022 |access-date=18 February 2022|archive-date=18 February 2022|archive-url=https://web.archive.org/web/20220218195020/https://blogs.nasa.gov/webb/2022/02/18/webb-team-brings-18-dots-of-starlight-into-hexagonal-formation/|url-status=live}}</ref> and a week later, phases 2 and 3 were also completed.<ref name="Webb blog 2022-02-25">{{Cite web |date=2022-02-25 |title=Webb Mirror Alignment Continues Successfully – James Webb Space Telescope |url=https://blogs.nasa.gov/webb/2022/02/25/webb-mirror-alignment-continues-successfully/ |access-date=2023-08-02 |website=blogs.nasa.gov |language=en-US}}</ref> This meant the 18 segments were working in unison, however until all 7 phases are complete, the segments were still acting as 18 smaller telescopes rather than one larger one.<ref name="Webb blog 2022-02-25" /> At the same time as the primary mirror was being commissioned, hundreds of other instrument commissioning and calibration tasks were also ongoing.<ref name="Webb blog 2022-02-24">{{Cite web |date=2022-02-24 |title=To Find the First Galaxies, Webb Pays Attention to Detail and Theory – James Webb Space Telescope |url=https://blogs.nasa.gov/webb/2022/02/24/to-find-the-first-galaxies-webb-pays-attention-to-detail-and-theory/ |access-date=2023-08-02 |website=blogs.nasa.gov |language=en-US}}</ref>

<gallery align="left" mode="packed" heights="125">
File:JWST - First images of HD 84406 (segments marked).png|Phase 1 interim image, annotated with the related mirror segments that took each image
File:JWST - Images of HD 84406 after phase 1 alignment (segments marked).png|Phase 1 annotated completion image of HD 84406
File:JWST commissioning - HD 84406 animated segment alignment.gif|Phase 2 completion, showing "before and after" effects of segment alignment
File:JWST commissioning - HD 84406 after image stacking.jpg|Phase 3 completion, showing 18 segments "stacked" as a single image of HD 84406
File:JWST Telescope alignment evaluation image labeled.jpg|Star 2MASS J17554042+6551277{{efn|2MASS J17554042+6551277 is a [[star]] in the constellation [[Draco (constellation)|Draco]], in the [[Milky Way]]. It is located almost 2,000 [[Light-year|light years]] away from [[Earth]], within a degree of the [[orbital pole|north ecliptic pole]].<!--not the celestial pole--> Its visual [[apparent magnitude]] ''m''<sub>v</sub> is 10.95, which makes it much too faint to be observed with the naked eye. It is cooler than the [[Sun]], but some 13 to 16 times brighter in visible light,<ref name="klu1">{{cite magazine |last1=Kluger |first1=Jeffrey |title=The James Webb Space Telescope Took Its Best Picture Yet |url=https://time.com/6158745/james-webb-space-telescope-picture/ |access-date=21 March 2022  |magazine=Time |date=18 March 2022 |archive-date=21 March 2022 |archive-url=https://web.archive.org/web/20220321013150/https://time.com/6158745/james-webb-space-telescope-picture/ |url-status=live }}</ref> and is consequently not a [[solar analogue|sun-like star]].}} captured by NIRCam instrument
File:JWST Nircam alignment selfie labeled.jpg|A "selfie" taken by the NIRCam during the alignment process
File:MIRI test image of the Large Magellanic Cloud - Spitzer vs webb LMC.png|alt=Image comparison between "old" Spitzer and new JWST|Image comparison between "old" [[Spitzer Space Telescope|Spitzer]] and new Webb<ref name="UT-20220502">{{cite news |last=Atkinson |first=Nancy |title=Now, We can Finally Compare Webb to Other Infrared Observatories |url=https://www.universetoday.com/155686/now-we-can-finally-compare-webb-to-other-infrared-observatories/ |date=2 May 2022 |work=[[Universe Today]] |access-date=12 May 2022 |archive-date=10 May 2022 |archive-url=https://web.archive.org/web/20220510035557/https://www.universetoday.com/155686/now-we-can-finally-compare-webb-to-other-infrared-observatories/ |url-status=live }}</ref>
File:Webb in Full Focus.jpg|Alignment of the NASA/ESA/CSA James Webb Space Telescope's sensors<ref>{{cite web | url=https://www.esa.int/ESA_Multimedia/Images/2022/04/Webb_in_full_focus | title=Webb in full focus | access-date=13 September 2022 | archive-date=13 September 2022 | archive-url=https://web.archive.org/web/20220913222229/https://www.esa.int/ESA_Multimedia/Images/2022/04/Webb_in_full_focus | url-status=live }}</ref>
File:Fine Guidance Sensor Test Image.jpg|Webb's Fine Guidance Sensor (FGS)<ref>{{cite web | url=https://blogs.nasa.gov/webb/2022/07/06/webbs-fine-guidance-sensor-provides-a-preview/ | title=Webb's Fine Guidance Sensor Provides a Preview – James Webb Space Telescope | date=6 July 2022 | access-date=13 September 2022 | archive-date=21 September 2022 | archive-url=https://web.archive.org/web/20220921160735/https://blogs.nasa.gov/webb/2022/07/06/webbs-fine-guidance-sensor-provides-a-preview/ | url-status=live }}</ref>
</gallery>

== Allocation of observation time ==
Webb observing time is allocated through a General Observers (GO) program, a Guaranteed Time Observations (GTO) program, a Director's Discretionary Early Release Science (DD-ERS) program,<ref>{{cite web|title=Calls for Proposals & Policy|url=https://jwst.stsci.edu/science-planning/calls-for-proposals-and-policy|publisher=Space Telescope Science Institute|access-date=13 November 2017|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144546/https://www.stsci.edu/jwst/science-planning/calls-for-proposals-and-policy|url-status=live}} {{PD-notice}}</ref> a calibration program, and a Director's Discretionary Time (DDT) program.<ref>{{cite web | url=https://www.stsci.edu/jwst/science-execution/approved-programs | title=Approved Programs }}</ref> The GTO program provides guaranteed observing time for scientists who developed hardware and software components for the observatory. The GO program provides all astronomers the opportunity to apply for observing time and will represent the bulk of the observing time. GO programs are selected through peer review by a Time Allocation Committee (TAC), similar to the proposal review process used for the Hubble Space Telescope. The DDT program is used for time-critical observations.

=== Early Release Science program ===
In November 2017, the Space Telescope Science Institute announced the selection of 13 Director's Discretionary Early Release Science (DD-ERS) programs, chosen through a competitive proposal process.<ref>{{cite web|title=Selections Made for the JWST Director's Discretionary Early Release Science Program|url=https://jwst.stsci.edu/news-events/news/News%20items/selections-made-for-the-jwst-directors-discretionary-early-release-science-program|publisher=Space Telescope Science Institute|access-date=13 November 2017|archive-url=https://wayback.archive-it.org/all/20180808190059/https://jwst.stsci.edu/news-events/news/News%2520items/selections-made-for-the-jwst-directors-discretionary-early-release-science-program|archive-date=8 August 2018|url-status=dead}} {{PD-notice}}</ref><ref>{{cite web|title=Director's Discretionary Early Release Science Programs|url=https://www.stsci.edu/jwst/science-execution/approved-ers-programs|publisher=Space Telescope Science Institute|access-date=26 December 2021|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144545/https://www.stsci.edu/jwst/science-execution/approved-ers-programs|url-status=live}}</ref> The observations for these programs&nbsp;– '''Early Release Observations''' (ERO)<ref name="MNRAS-20230101">{{cite journal |author=Adams |first=N. J. |display-authors=et al |date=January 2023 |title=Discovery and properties of ultra-high redshift galaxies (9 < z < 12) in the JWST ERO SMACS 0723 Field |url=https://academic.oup.com/mnras/article/518/3/4755/6835532 |url-status=live |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=518 |issue=3 |pages=4755–4766 |arxiv=2207.11217 |doi=10.1093/mnras/stac3347 |doi-access=free |archive-url=https://web.archive.org/web/20230102161226/https://academic.oup.com/mnras/article/518/3/4755/6835532 |archive-date=2 January 2023 |accessdate=2 January 2023}}</ref><ref name="Yan2023">{{cite journal|title=First Batch of z ≈ 11–20 Candidate Objects Revealed by the James Webb Space Telescope Early Release Observations on SMACS 0723-73|first=Haojing|last=Yan|display-authors=etal|journal=The Astrophysical Journal Letters|date=January 2023|volume=942|issue=L9|pages=20|doi-access=free|doi=10.3847/2041-8213/aca80c|arxiv=2207.11558|bibcode=2023ApJ...942L...9Y}}</ref> – were to be obtained during the first five months of Webb science operations after the end of the commissioning period. A total of 460 hours of observing time was awarded to these 13 programs, which span science topics including the [[Solar System]], [[exoplanet]]s, [[star]]s and [[star formation]], nearby and distant [[Galaxy|galaxies]], [[gravitational lens]]es, and [[quasar]]s. These 13 ERS programs were to use a total of 242.8 hours of observing time on the telescope (not including Webb observing overheads and [[Slew (spacecraft)|slew]] time).

{| class="wikitable"
|+ Early Release Science programs
|- style="font-size: smaller;"
!Name
![[Principal investigator|Principal Investigator]]
!Category
!Observation time (hours)
|- style="text-align:center;"
| style="text-align:left;"| Radiative Feedback from Massive Stars as Traced by Multiband Imaging and Spectroscopic Mosaics
| {{ill|Olivier Berné|fr}}
| Stellar Physics
| 8.3<ref>{{cite web |title=Radiative Feedback from Massive Stars as Traced by Multiband Imaging and Spectroscopic Mosaic |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1288-berne.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144623/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1288-berne.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| IceAge: Chemical Evolution of Ices during Star Formation
| [[Melissa McClure (astronomer)|Melissa McClure]]
| Stellar Physics
| 13.4<ref>{{cite web |title=IceAge: Chemical Evolution of Ices during Star Formation |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1309-mcclure.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144623/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1309-mcclure.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| Through the Looking GLASS: A JWST Exploration of Galaxy Formation and Evolution from Cosmic Dawn to Present Day
| [[Tommaso Treu]]
| Galaxies and the [[Warm–hot intergalactic medium|IGM]]
| 24.3<ref>{{cite web |title=Through the Looking GLASS: A JWST Exploration of Galaxy Formation and Evolution from Cosmic Dawn to Present Day |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1324-treu.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144623/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1324-treu.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| A JWST Study of the Starburst-AGN Connection in Merging LIRGs
| [[Lee Armus]]
| Galaxies and the IGM
| 8.7<ref>{{cite web |title=A JWST Study of the Starburst-AGN Connection in Merging LIRGs |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1328-armus.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144624/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1328-armus.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| The Resolved Stellar Populations Early Release Science Program
| [[Daniel Weisz]]
| Stellar Populations
| 20.3<ref>{{cite web |title=The Resolved Stellar Populations Early Release Science Program |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1334-weisz.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144624/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1334-weisz.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| Q-3D: Imaging Spectroscopy of Quasar Hosts with JWST Analyzed with a Powerful New PSF Decomposition and Spectral Analysis Package
| [[Dominika Wylezalek]]
| Massive Black Holes and their Galaxies
| 17.4<ref>{{cite web |title=Q-3D: Imaging Spectroscopy of Quasar Hosts with JWST Analyzed with a Powerful New PSF Decomposition and Spectral Analysis Package |author=Dominika Wylezalek |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1335-wylezalek.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144624/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1335-wylezalek.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| The Cosmic Evolution Early Release Science (CEERS) Survey
| [[Steven Finkelstein]]
| Galaxies and the IGM
| 36.6<ref>{{cite web |title=The Cosmic Evolution Early Release Science (CEERS) Survey |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1345-finkelstein.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144624/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1345-finkelstein.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| Establishing Extreme Dynamic Range with JWST: Decoding Smoke Signals in the Glare of a Wolf-Rayet Binary
| [[Ryan Lau]]
| Stellar Physics
| 6.5<ref>{{cite web |title=Establishing Extreme Dynamic Range with JWST: Decoding Smoke Signals in the Glare of a Wolf-Rayet Binary |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1349-lau.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144625/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1349-lau.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star Formation
| [[Jane Rigby (astrophysicist)|Jane Rigby]]
| Galaxies and the IGM
| 26.0<ref>{{cite web |title=TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star Formation |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1355-rigby.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144625/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1355-rigby.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| Nuclear Dynamics of a Nearby Seyfert with NIRSpec Integral Field Spectroscopy
| [[Misty C. Bentz|Misty Bentz]]
| Massive Black Holes and their Galaxies
| 1.5<ref>{{cite web |title=Nuclear Dynamics of a Nearby Seyfert with NIRSpec Integral Field Spectroscopy |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1364-bentz.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144625/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1364-bentz.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| The Transiting Exoplanet Community Early Release Science Program
| [[Natalie Batalha]]
| Planets and Planet Formation
| 52.1<ref>{{cite web |title=The Transiting Exoplanet Community Early Release Science Program |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1366-batalha.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144626/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1366-batalha.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| ERS observations of the Jovian System as a Demonstration of JWST's Capabilities for Solar System Science
| [[Imke de Pater]]
| Solar System
| 9.3<ref>{{cite web |title=ERS observations of the Jovian System as a Demonstration of JWST's Capabilities for Solar System Science |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1373-depater.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144626/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1373-depater.pdf |url-status=live }}</ref>
|- style="text-align:center;"
| style="text-align:left;"| High Contrast Imaging of Exoplanets and Exoplanetary Systems with JWST
| [[Sasha Hinkley]]
| Planets and Planet Formation
| 18.4<ref>{{cite web |title=High Contrast Imaging of Exoplanets and Exoplanetary Systems with JWST |url=https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1386-hinkley.pdf |access-date=17 March 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144626/https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1386-hinkley.pdf |url-status=live }}</ref>
|}

=== General Observer Program ===
For GO Cycle 1 there were 6,000 hours of observation time available to allocate, and 1,173 proposals were submitted requesting a total of 24,500 hours of observation time.<ref>{{cite web |title=JWST Cycle 1 General Observer Submission Statistics |url=https://www.stsci.edu/contents/news/jwst/2020/jwst-cycle-1-general-observer-submission-statistics |publisher=Space Telescope Science Institute |access-date=10 January 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144630/https://www.stsci.edu/contents/news/jwst/2020/jwst-cycle-1-general-observer-submission-statistics |url-status=live }}</ref> Selection of Cycle 1 GO programs was announced on 30 March 2021, with 266 programs approved. These included 13 large programs and treasury programs producing data for public access.<ref>{{cite web|title=STScI Announces the JWST Cycle 1 General Observer Program|url=https://www.stsci.edu/contents/news/jwst/2021/stsci-announces-the-jwst-cycle-1-general-observer-program|access-date=30 March 2021|archive-date=15 July 2022|archive-url=https://web.archive.org/web/20220715144630/https://www.stsci.edu/contents/news/jwst/2021/stsci-announces-the-jwst-cycle-1-general-observer-program|url-status=live}}</ref> The Cycle 2 GO program was announced on 10 May 2023.<ref>{{cite web |title=STScI Announces the JWST Cycle 2 General Observer Program |url=https://www.stsci.edu/contents/news/jwst/2023/stsci-announces-the-jwst-cycle-2-general-observer-program |publisher=Space Telescope Science Institute |access-date=11 May 2023}}</ref> Webb science observations are nominally scheduled in weekly increments. The observation plan for every week is published on Mondays by the Space Telescope Science Institute.<ref>{{Cite web|url=https://www.stsci.edu/home/jwst/science-execution/observing-schedules|title=OBSERVING SCHEDULES|website=STScI.edu|access-date=15 January 2023|archive-date=7 November 2022|archive-url=https://web.archive.org/web/20221107185052/https://www.stsci.edu/home/jwst/science-execution/observing-schedules|url-status=live}}</ref> In Cycle 4 the telescope showed its continued popularity in the astronomy community by garnering 2,377 proposals for 78,000 hours of observing time, nine times more than the available amount.<ref>{{cite web |last1=Clark |first1=Stephen |title=Nearly three years since launch, Webb is a hit among astronomers |url=https://arstechnica.com/space/2024/11/more-and-more-astronomers-are-eager-to-use-the-james-webb-space-telescope/ |website=Ars Technica |date=6 November 2024}}</ref>

== Scientific results ==
The JWST completed its commissioning and began full scientific operations on 11 July 2022.<ref>{{Cite web |last1=Cesari |first1=Thaddeus |last2=Center |first2=NASA's Goddard Space Flight |date=2022-07-11 |title=At Last! NASA's Webb Space Telescope Is Now Fully Ready for Science |url=https://scitechdaily.com/?p=184319 |access-date=2023-02-18 |website=SciTechDaily |language=en-us}}</ref> With some exceptions, most experiment data is kept private for one year for the exclusive use of scientists running that particular experiment, and then the raw data is released to the public.<ref>{{Cite web |author1=Bartels |first=Meghan |date=2022-12-12 |title=NASA may unlock future James Webb Space Telescope data |url=https://www.space.com/james-webb-space-telescope-exclusive-data-controversy |access-date=2023-02-18 |website=Space.com |language=en-us}}</ref>{{Multiple images |width=250 |direction=vertical |align=right |header=Hubble (2017; top) compared to Webb (2022; bottom)<ref name="NBC-20220712">{{cite news |last1=Chow |first1=Denise |last2=Wu |first2=Jiachuan |title=Photos: How pictures from the Webb telescope compare to Hubble's - NASA's $10 billion telescope peers deeper into space than ever, revealing previously undetectable details in the cosmos. |url=https://www.nbcnews.com/data-graphics/compare-photos-nasas-james-webb-space-telescope-hubble-space-telescope-rcna37875 |date=12 July 2022 |work=[[NBC News]] |access-date=16 July 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715193545/https://www.nbcnews.com/data-graphics/compare-photos-nasas-james-webb-space-telescope-hubble-space-telescope-rcna37875 |url-status=live }}</ref><ref name="ABC-20220714">{{cite news |last1=Deliso |first1=Meredith |last2=Longo |first2=Meredith |last3=Rothenberg |first3=Nicolas |title=Hubble vs. James Webb telescope images: See the difference |url=https://abcnews.go.com/Technology/hubble-james-webb-telescope-images-difference/story?id=86763039 |date=14 July 2022 |work=[[ABC News (United States)|ABC News]] |access-date=15 July 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715003405/https://abcnews.go.com/Technology/hubble-james-webb-telescope-images-difference/story?id=86763039 |url-status=live }}</ref>
 |image1=NASA-HubbleSpaceTelescope-DeepField-2017.jpg |image2=Webb's First Deep Field (adjusted).jpg
 |footer=[[Webb's First Deep Field|Deep Field]] – [[Galaxy cluster]]<br />[[SMACS J0723.3-7327]]<ref name="NASA-20220711" /><ref name="NYT-20220711" /><ref name="SA-202207">{{cite news |last=Pacucci |first=Fabio |title=How Taking Pictures of 'Nothing' Changed Astronomy - Deep-field images of "empty" regions of the sky from Webb and other space telescopes are revealing more of the universe than we ever thought possible |url=https://www.scientificamerican.com/article/how-taking-pictures-of-nothing-changed-astronomy1/ |date=15 July 2022 |work=[[Scientific American]] |access-date=16 July 2022 |archive-date=16 July 2022 |archive-url=https://web.archive.org/web/20220716023339/https://www.scientificamerican.com/article/how-taking-pictures-of-nothing-changed-astronomy1/ |url-status=live }}</ref><ref name="CNET-20120713">{{cite news |last=Kooser |first=Amanda |title=Hubble and James Webb Space Telescope Images Compared: See the Difference - The James Webb Space Telescope builds on Hubble's legacy with stunning new views of the cosmos. |url=https://www.cnet.com/pictures/hubble-and-james-webb-space-telescope-images-compared-see-the-difference/ |date=13 July 2012 |work=[[CNET]] |access-date=16 July 2022 |archive-date=17 July 2022 |archive-url=https://web.archive.org/web/20220717015540/https://www.cnet.com/pictures/hubble-and-james-webb-space-telescope-images-compared-see-the-difference/ |url-status=live }}</ref><ref name="UT-20220502"/>}} JWST observations substantially advanced understanding of exoplanets, the first billion years of the universe,<ref>{{cite arXiv |last1=Adamo |first1=Angela |last2=Atek |first2=Hakim |last3=Bagley |first3=Micaela B. |last4=Bañados |first4=Eduardo |last5=Barrow |first5=Kirk S. S. |last6=Berg |first6=Danielle A. |last7=Bezanson |first7=Rachel |last8=Bradač |first8=Maruša |last9=Brammer |first9=Gabriel |last10=Carnall |first10=Adam C. |last11=Chisholm |first11=John |last12=Coe |first12=Dan |last13=Dayal |first13=Pratika |last14=Eisenstein |first14=Daniel J. |last15=Eldridge |first15=Jan J. |last16=Ferrara |first16=Andrea |last17=Fujimoto |first17=Seiji |last18=de Graaff |first18=Anna |last19=Habouzit |first19=Melanie |last20=Hutchison |first20=Taylor A. |last21=Kartaltepe |first21=Jeyhan S. |last22=Kassin |first22=Susan A. |last23=Kriek |first23=Mariska |last24=Labbé |first24=Ivo |last25=Maiolino |first25=Roberto |last26=Marques-Chaves |first26=Rui |last27=Maseda |first27=Michael V. |last28=Mason |first28=Charlotte |last29=Matthee |first29=Jorryt |last30=McQuinn |first30=Kristen B. W. |last31=Meynet |first31=Georges |last32=Naidu |first32=Rohan P. |last33=Oesch |first33=Pascal A. |last34=Pentericci |first34=Laura |last35=Pérez-González |first35=Pablo G. |last36=Rigby |first36=Jane R. |last37=Roberts-Borsani |first37=Guido |last38=Schaerer |first38=Daniel |last39=Shapley |first39=Alice E. |last40=Stark |first40=Daniel P. |last41=Stiavelli |first41=Massimo |last42=Strom |first42=Allison L. |last43=Vanzella |first43=Eros |last44=Wang |first44=Feige |last45=Wilkins |first45=Stephen M. |last46=Williams |first46=Christina C. |last47=Willott |first47=Chris J. |last48=Wylezalek |first48=Dominika |last49=Nota |first49=Antonella |title=The First Billion Years, According to JWST |date=31 May 2024 |class=astro-ph.GA |eprint=2405.21054}}</ref> and other astrophysical and cosmological phenomena.

=== First full-color images ===
The first full-color images and spectroscopic data were released on 12 July 2022, which also marked the official beginning of Webb's general science operations. U.S. President [[Joe Biden]] revealed the first image, ''[[Webb's First Deep Field]]'', on 11 July 2022.<ref name="NASA-20220711">{{cite news |last=Garner |first=Rob |title=NASA's Webb Delivers Deepest Infrared Image of Universe Yet |url=https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet |date=11 July 2022 |work=[[NASA]] |access-date=12 July 2022 |archive-date=12 July 2022 |archive-url=https://web.archive.org/web/20220712000119/https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet/ |url-status=live }}</ref><ref name="NYT-20220711">{{cite news |last1=Overbye |first1=Dennis |last2=Chang |first2=Kenneth |last3=Tankersley |first3=Jim |title=Biden and NASA Share First Webb Space Telescope Image – From the White House on Monday, humanity got its first glimpse of what the observatory in space has been seeing: a cluster of early galaxies. |url=https://www.nytimes.com/2022/07/11/science/nasa-webb-telescope-images-livestream.html |date=11 July 2022 |work=[[The New York Times]] |access-date=12 July 2022 |archive-date=12 July 2022 |archive-url=https://web.archive.org/web/20220712005736/https://www.nytimes.com/2022/07/11/science/nasa-webb-telescope-images-livestream.html |url-status=live }}</ref> Additional releases around this time include:<ref>{{cite web |last=Timmer |first=John |date=2022-07-08 |title=NASA names first five targets for Webb images |url=https://arstechnica.com/science/2022/07/nasa-names-first-five-targets-for-webb-images/ |access-date=2022-07-08 |website=Ars Technica |language=en-us |archive-date=8 July 2022 |archive-url=https://web.archive.org/web/20220708195443/https://arstechnica.com/science/2022/07/nasa-names-first-five-targets-for-webb-images/ |url-status=live }}</ref><ref name="first">{{cite web |date=2022-07-08 |title=First Images from the James Webb Space Telescope |url=https://www.nasa.gov/webbfirstimages |access-date=2022-07-08 |website=NASA |archive-date=13 July 2022 |archive-url=https://web.archive.org/web/20220713043735/https://www.nasa.gov/webbfirstimages/ |url-status=live }}</ref><ref name="NYT-20220712">{{cite news |last=Stirone |first=Shannon |title=Gawking in Awe at the Universe, Together |url=https://www.nytimes.com/2022/07/12/opinion/nasa-james-webb-space-telescope-awe.html#permid=119279300 |date=12 July 2022 |work=[[The New York Times]] |access-date=13 July 2022 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715144629/https://www.nytimes.com/2022/07/12/opinion/nasa-james-webb-space-telescope-awe.html#permid=119279300 |url-status=live }}</ref>
* [[Carina Nebula]] {{ndash}} young, star-forming region called [[NGC 3324]] about 8,500 light-years from Earth, described by NASA as "Cosmic Cliffs".
* [[WASP-96b]] {{ndash}} including an analysis of atmosphere with evidence of water around a [[Gas giant|giant gas]] planet orbiting a distant star 1,120 light-years from Earth.
* [[Southern Ring Nebula]] {{ndash}} clouds of gas and dust expelled by a dying star 2,500 light-years from Earth.
* [[Stephan's Quintet]] {{ndash}} a visual display of five galaxies with colliding gas and dust clouds creating new stars; four central galaxies are 290 million light-years from Earth.
* [[SMACS J0723.3-7327]] {{ndash}} a [[galaxy cluster]] at redshift 0.39, with distant background galaxies whose images are distorted and magnified due to [[gravitational lensing]] by the cluster. This image has been called ''Webb's First Deep Field''. It was later discovered that in this picture were three ancient galaxies that existed shortly after the Big Bang. The images of these distant galaxies are views of the universe 13.1 billion years ago.<ref name=first/><ref>{{cite news |last1=Overbye |first1=Dennis |last2=Chang |first2=Kenneth |last3=Sokol |first3=Joshua |date=12 July 2022 |title=Webb Telescope Reveals a New Vision of an Ancient Universe |work=The New York Times |url=https://www.nytimes.com/2022/07/12/science/james-webb-telescope-images-nasa.html?smid=url-share |url-status=live |access-date=13 July 2022 |archive-url=https://web.archive.org/web/20220715144629/https://www.nytimes.com/2022/07/12/science/james-webb-telescope-images-nasa.html?smid=url-share |archive-date=15 July 2022}}</ref><ref>{{cite news |last1=Grossman |first1=Lisa |date=12 January 2023 |title=The James Webb telescope found 'Green Pea' galaxies in the early universe |work=Science News |url=https://www.sciencenews.org/article/webb-telescope-green-pea-galaxies-universe |access-date=5 Dec 2023}}</ref>
On 14 July 2022, NASA presented images of [[Jupiter]] and related areas by the JWST, including infrared views.<ref name="NYT-20220715">{{cite news |last=Chang |first=Kenneth |date=15 July 2022 |title=NASA Shows Webb's View of Something Closer to Home: Jupiter – The powerful telescope will help scientists make discoveries both within our solar system and well beyond it. |work=[[The New York Times]] |url=https://www.nytimes.com/2022/07/15/science/webb-telescope-jupiter-images.html |url-status=live |access-date=16 July 2022 |archive-url=https://web.archive.org/web/20220716000145/https://www.nytimes.com/2022/07/15/science/webb-telescope-jupiter-images.html/ |archive-date=16 July 2022}}</ref>

In a preprint released around the same time, NASA, ESA and CSA scientists stated that "the science performance of JWST is better than expected". The document stated that during the commissioning, the instruments captured spectra of transiting exoplanets with a precision better than 1000 ppm per data point, and tracked moving objects with speeds up to 67 milliarcseconds/second, more than twice as fast as the requirement.{{efn|name= tracking }} It also obtained the spectra of hundreds of stars simultaneously in a dense field towards the [[Milky Way]]'s [[Galactic Center]]. Other targets included:<ref name="Rigby 2022-07-12">{{cite journal |last1=Rigby |first1=Jane |last2=Perrin |first2=Marshall |last3=McElwain |first3=Michael |last4=Kimble |first4=Randy |last5=Friedman |first5=Scott |last6=Lallo |first6=Matt |last7=Doyon |first7=René |last8=Feinberg |first8=Lee |last9=Ferruit |first9=Pierre |last10=Glasse |first10=Alistair |last11=Rieke |first11=Marcia |last12=Rieke |first12=George |display-authors=etal |title=The Science Performance of JWST as Characterized in Commissioning |journal=Publications of the Astronomical Society of the Pacific |year=2023 |volume=135 |issue=1046 |page=048001 |doi=10.1088/1538-3873/acb293 |arxiv=2207.05632|bibcode=2023PASP..135d8001R |s2cid=253735464 }}</ref>
* Moving targets: [[Jupiter's rings]] and moons (particularly [[Europa (moon)|Europa]], [[Thebe (moon)|Thebe]] and [[Metis (moon)|Metis]]), [[asteroid]]s [[2516 Roman]], [[118 Peitho]], [[6481 Tenzing]], [[1773 Rumpelstilz]], [[216 Kleopatra]], [[2035 Stearns]], [[4015 Wilson–Harrington|4015 Wilson-Harrington]] and {{mpl|2004 JX|20}}
* [[NIRCam]] [[grism]] time-series, NIRISS SOSS and [[NIRSpec]] BOTS mode: the Jupiter-sized planet [[HAT-P-14b]]
* NIRISS [[aperture masking interferometry]] (AMI): A clear detection of the very low-mass companion star [[AB Doradus]] C, which had a separation of only 0.3 [[Minute and second of arc|arcseconds]] to the primary. This observation was the first demonstration of AMI in space.
* MIRI low-resolution spectroscopy (LRS): a hot [[super-Earth]] planet [[L 168-9 b]] (TOI-134) around a bright [[Red dwarf|M-dwarf]] star ([[red dwarf]] star)<ref>{{cite journal |last1=Astudillo-Defru |first1=N. |last2=Cloutier |first2=R. |last3=Wang |first3=S. X. |last4=Teske |first4=J. |last5=Brahm |first5=R. |last6=Hellier |first6=C. |last7=Ricker |first7=G. |last8=Vanderspek |first8=R. |last9=Latham |first9=D. |last10=Seager |first10=S. |last11=Winn |first11=J. N. |display-authors=etal |date=2020-04-01 |title=A hot terrestrial planet orbiting the bright M dwarf L 168-9 unveiled by TESS |url=https://ui.adsabs.harvard.edu/abs/2020A&A...636A..58A |journal=Astronomy and Astrophysics |volume=636 |pages=A58 |doi=10.1051/0004-6361/201937179 |arxiv=2001.09175 |bibcode=2020A&A...636A..58A |s2cid=210920549 |issn=0004-6361 |access-date=15 July 2022 |archive-date=8 March 2022 |archive-url=https://web.archive.org/web/20220308154037/https://ui.adsabs.harvard.edu/abs/2020A%26A...636A..58A |url-status=live }}</ref>

=== Bright early galaxies ===
Within two weeks of the first Webb images, several preprint papers described a wide range of high redshift and very luminous (presumably large) galaxies believed to date from 235 million years (z=16.7) to 280 million years after the Big Bang, far earlier than previously known.<ref name="MNRAS-20230101" /><ref name="Yan2023" /> On 17 August 2022, NASA released a large mosaic image of 690 individual frames taken by the NIRCam on Webb of numerous very early galaxies.<ref name="UT-20220817">{{cite news |last=Atkinson |first=Nancy |title=Here's the Largest Image JWST Has Taken So Far |url=https://www.universetoday.com/157168/heres-the-largest-image-jwst-has-taken-so-far/ |date=17 August 2022 |work=[[Universe Today]] |access-date=18 August 2022 |archive-date=17 August 2022 |archive-url=https://web.archive.org/web/20220817215842/https://www.universetoday.com/157168/heres-the-largest-image-jwst-has-taken-so-far/ |url-status=live }}</ref><ref name="ES-20220818">{{cite news |last=Whitt |first=Kelly Kizer |title=Webb's largest image of galaxies yet |url=https://earthsky.org/space/webb-largest-image-of-galaxies-yet/ |date=18 August 2022 |work=[[Earth & Sky]] |access-date=19 August 2022 |archive-date=19 August 2022 |archive-url=https://web.archive.org/web/20220819020446/https://earthsky.org/space/webb-largest-image-of-galaxies-yet/ |url-status=live }}</ref> Some early galaxies observed by Webb like [[CEERS-93316]], which was believed to have an estimated [[photometric redshift]] of approximately z=16.7 corresponding to 235.8 million years after the Big Bang, are high redshift galaxy candidates.<ref name="EDIN-20220801">{{cite news |author=<!--Not stated--> |date=1 August 2022 |title=Edinburgh astronomers find most distant galaxy – Early data from a new space telescope has enabled Edinburgh astronomers to locate the most distant galaxy ever found. |work=[[University of Edinburgh]] |url=https://www.ed.ac.uk/news/2022/edinburgh-astronomers-find-most-distant-galaxy |url-status=live |access-date=18 August 2022 |archive-url=https://web.archive.org/web/20220809223854/https://www.ed.ac.uk/news/2022/edinburgh-astronomers-find-most-distant-galaxy |archive-date=9 August 2022}}</ref><ref name="Planck 2018age">
{{cite journal
 |author=Planck Collaboration
 |year=2020
 |title=Planck 2018 results. VI.&nbsp;Cosmological parameters
 |journal=Astronomy & Astrophysics
 |volume=641 |at=page&nbsp;A6 (see PDF page&nbsp;15, Table&nbsp;2: "Age/Gyr", last&nbsp;column)
 |doi=10.1051/0004-6361/201833910
 |arxiv=1807.06209 |bibcode=2020A&A...641A...6P
 |s2cid=119335614
}}</ref> However, for CEERS-93316 specifically, a later [[spectroscopic redshift]] measurement revealed a more accurate redshift value of approximately z=4.91.<ref>{{Cite journal |last1=Arrabal Haro |first1=Pablo |last2=Dickinson |first2=Mark |last3=Finkelstein |first3=Steven L. |last4=Kartaltepe |first4=Jeyhan S. |last5=Donnan |first5=Callum T. |last6=Burgarella |first6=Denis |last7=Carnall |first7=Adam C. |last8=Cullen |first8=Fergus |last9=Dunlop |first9=James S. |last10=Fernández |first10=Vital |last11=Fujimoto |first11=Seiji |last12=Jung |first12=Intae |last13=Krips |first13=Melanie |last14=Larson |first14=Rebecca L. |last15=Papovich |first15=Casey |date=2023-10-26 |title=Confirmation and refutation of very luminous galaxies in the early Universe |url=https://www.nature.com/articles/s41586-023-06521-7 |journal=Nature |language=en |volume=622 |issue=7984 |pages=707–711 |doi=10.1038/s41586-023-06521-7 |pmid=37579792 |issn=0028-0836|arxiv=2303.15431 |bibcode=2023Natur.622..707A }}</ref> In September 2022, [[primordial black hole]]s were proposed as explaining these unexpectedly large and early galaxies.<ref name="jwst1">{{Cite journal |last1=Liu |first1=Boyuan |last2=Bromm |first2=Volker |date=2022-09-27 |title=Accelerating Early Massive Galaxy Formation with Primordial Black Holes |journal=The Astrophysical Journal Letters |language=en |volume=937 |issue=2 |pages=L30 |doi=10.3847/2041-8213/ac927f |arxiv=2208.13178 |bibcode=2022ApJ...937L..30L |s2cid=252355487 |issn=2041-8205 |doi-access=free }}</ref><ref name="jwst2">{{Cite journal |last1=Yuan |first1=Guan-Wen |last2=Lei |first2=Lei |last3=Wang |first3=Yuan-Zhu |last4=Wang |first4=Bo |last5=Wang |first5=Yi-Ying |last6=Chen |first6=Chao |last7=Shen |first7=Zhao-Qiang |last8=Cai |first8=Yi-Fu |last9=Fan |first9=Yi-Zhong |date=2024 |title=Rapidly growing primordial black holes as seeds of the massive high-redshift JWST Galaxies |journal=Science China Physics, Mechanics & Astronomy |volume=67 |issue=10 |doi=10.1007/s11433-024-2433-3 |arxiv=2303.09391 |bibcode=2024SCPMA..6709512Y }}</ref><ref>{{cite arXiv |last1=Su |first1=Bing-Yu |last2=Li |first2=Nan |last3=Feng |first3=Lei |title=An inflation model for massive primordial black holes to interpret the JWST observations |date=2023 |class=astro-ph.CO |eprint=2306.05364 }}</ref> In May 2024, the JWST identified the most distant known galaxy, JADES-GS-z14-0,<ref name=":2">{{Cite web |date=2024-05-30 |title=NASA's James Webb Space Telescope Finds Most Distant Known Galaxy - James Webb Space Telescope |url=https://blogs.nasa.gov/webb/2024/05/30/nasas-james-webb-space-telescope-finds-most-distant-known-galaxy/ |access-date=2024-05-31 |website=blogs.nasa.gov |language=en-US}}</ref> seen just 290 million years after the Big Bang, corresponding to a redshift of 14.32. Part of the JWST Advanced Deep Extragalactic Survey (JADES), this discovery highlights a galaxy significantly more luminous and massive than expected for such an early period. Detailed analysis using JWST's NIRSpec and MIRI instruments revealed this galaxy's remarkable properties, including its significant size and dust content, challenging current models of early galaxy formation.<ref name=":2" />

=== Subsequent noteworthy observations and interpretations ===
In June 2023, detection of organic molecules 12 billion light-years away in the [[SPT0418-47]] galaxy was announced.<ref>{{Cite web |last=Strickland |first=Ashley |date=2023-06-06 |title=Webb telescope detects organic molecules in distant galaxy |url=https://www.cnn.com/2023/06/06/world/webb-telescope-distant-organic-molecules-scn/index.html |access-date=2023-06-06 |website=CNN |language=en}}</ref>

On 12 July 2023, NASA celebrated the first year of operations with the release of Webb's image of a small star-forming region in the [[Rho Ophiuchi cloud complex]], 390 light years away.<ref>{{Cite web |last=Grey |first=Charles |date=2023-07-15 |title=James Webb Space Telescope Marks First Year of Science Operations |url=https://airspacenews.net/james-webb-space-telescope-marks-first-year-of-science-operations/ |access-date=2023-07-22 |website=AIR SPACE News |language=en-US}}</ref>

In December 2023, NASA released Christmas holiday-related images by JWST, including the [[NGC 2264|Christmas Tree Galaxy Cluster]] and others.<ref name="NYT-20231219">{{cite news |last=Miller |first=Katrina |title=It's Christmastime in the Cosmos - Astronomers have a long tradition of finding holiday cheer in outer space. |url=https://www.nytimes.com/2023/12/19/science/christmas-stars-galaxies-webb-nasa.html |date=19 December 2023 |work=[[The New York Times]] |url-status=live |archiveurl=https://archive.today/20231219114751/https://www.nytimes.com/2023/12/19/science/christmas-stars-galaxies-webb-nasa.html |archivedate=19 December 2023 |accessdate=19 December 2023 }}</ref>

In May 2024, the JWST detected the farthest known black hole merger.<ref>{{Cite web |title=Webb detects most distant black hole merger to date |url=https://www.esa.int/Science_Exploration/Space_Science/Webb/Webb_detects_most_distant_black_hole_merger_to_date |access-date=2024-05-19 |website=www.esa.int |language=en}}</ref> Occurring within the galaxy system ZS7, 740 million years after the Big Bang, this discovery suggests a fast growth rate for black holes through mergers, even in the young Universe.{{original research inline|date=February 2025}}

== Gallery ==
<gallery mode="packed" heights="100" caption="First images by the James Webb Space Telescope – released 12 July 2022">
File:NASA’s Webb Reveals Cosmic Cliffs, Glittering Landscape of Star Birth.jpg|Cosmic Cliffs of [[Carina Nebula]] ([[NGC 3324]]) (NIRCam)
File:NASA’s Webb Reveals Cosmic Cliffs, Glittering Landscape of Star Birth - Flickr - James Webb Space Telescope.png|[[Carina Nebula]] ([[NGC 3324]]) (MIRI)
File:NASA’s Webb Captures Dying Star’s Final ‘Performance’ in Fine Detail.png|[[Southern Ring Nebula]] ([[NGC 3132]]; Left: NIRCam; Right: MIRI)
File:Webb’s First Deep Field (MIRI and NIRCam Images Side by Side).png|[[Webb's First Deep Field]] ([[SMACS 0723]]; Left: [[MIRI (Mid-Infrared Instrument)|MIRI]]; Right: [[NIRCam]])
File:Stephan's Quintet taken by James Webb Space Telescope.jpg|[[Stephan's Quintet]] (NIRCam/MIRI composite)
File:Exoplanet WASP-96 b (NIRISS Transmission Spectrum) (weic2206a).jpeg|Spectrum of [[WASP-96b]]
</gallery>

{{center|{{commons category-inline|Images by the James Webb Space Telescope}}}}

== See also ==
<!-- alphabetical order please [[WP:SEEALSO]] -->
<!-- please add a short description [[WP:SEEALSO]], via {{subst:AnnotatedListOfLinks}} or {{Annotated link}} -->
{{div col|colwidth=20em}}
* [[Collier Trophy]] – to JWST in 2023
* {{Annotated link |Libration point orbit}}
* {{Annotated link |List of deep fields}}
* [[List of largest infrared telescopes]]
* [[List of largest optical reflecting telescopes]]
* [[List of space telescopes]]
* [[Lunar Crater Radio Telescope]] - proposed telescope on the far side of the Moon in a crater 
* [[Nancy Grace Roman Space Telescope]] – planned launch no later than May 2027
* [[New Worlds Mission]] – proposed occulter for the JWST
* {{section link| Pea galaxy| 2023}}
* {{Annotated link |Physical cosmology}}
* {{Annotated link |Satellite bus}}
* {{Annotated link |Solar panels on spacecraft}}
* {{Annotated link |Spacecraft design}}
* {{Annotated link |Spacecraft attitude control}}
* {{Annotated link |Spacecraft thermal control}}
* [[Timeline of the James Webb Space Telescope]]
* ''[[Unknown: Cosmic Time Machine]]'', Netflix documentary about the James Webb Space Telescope{{div col end}}
<!-- alphabetical order please [[WP:SEEALSO]] -->

== Notes ==
{{Notelist}}

== References ==
{{Reflist}}

== Further reading ==
* {{cite journal |title=The James Webb Space Telescope |author=Gardner |first=Jonathan P. |s2cid=118865272 |display-authors=et al |doi=10.1007/s11214-006-8315-7 |journal=Space Science Reviews |volume=123 |issue=4 |date=November 2006 |pages=484–606 |arxiv=astro-ph/0606175 |bibcode=2006SSRv..123..485G}} The formal case for JWST science presented in 2006.
* {{cite journal |title=Scientific discovery with the James Webb Space Telescope |author=Kalirai |first=Jason |s2cid=85539627 |doi=10.1080/00107514.2018.1467648 |journal=Contemporary Physics |volume=59 |issue=3 |date=April 2018 |pages=259–290 |arxiv=1805.06941 |bibcode=2018ConPh..59..251K}} A review of JWST capabilities and scientific opportunities.
* {{cite journal |last1=Rigby |first1=Jane |last2=Perrin |first2=Marshall |last3=McElwain |first3=Michael |last4=Kimble |first4=Randy |last5=Friedman |first5=Scott |display-authors=etal |title=The Science Performance of JWST as Characterized in Commissioning |journal=Publications of the Astronomical Society of the Pacific |year=2023 |volume=135 |issue=1046 |page=048001 |doi=10.1088/1538-3873/acb293 |arxiv=2207.05632|bibcode=2023PASP..135d8001R |s2cid=253735464 }}

== External links ==
{{commons}}
* Official [https://jwst.nasa.gov/content/webbLaunch/index.html NASA] / [https://webbtelescope.org/ STScI] / [https://www.esa.int/Science_Exploration/Space_Science/Webb ESA] / [https://jwst.fr/ French] website
* [https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html?units=metric JWST NASA – Tracking Page − Launch to Final Calibrations] (and more)
* [https://jwst.nasa.gov/content/about/orbit.html JWST NASA – About page] − Timeline details / Webb orbit / L2 / Communicating
* [https://archive.today/20211230000734/https://medium.com/starts-with-a-bang/5-critical-moments-will-determine-the-success-or-failure-of-nasas-james-webb-space-telescope-b405414a062b JWST Text – Most Critical Events – Launching and Deployment] (2021)
* [https://www.youtube.com/watch?v=aICaAEXDJQQ JWST Video (031:22): Highlights − Technical Engineering Details] (2021)
* [https://www.youtube.com/watch?v=v6ihVeEoUdo JWST Video (012:02): 1st Month – Launching and Deployment] (animation; 2017)
* [https://www.youtube.com/watch?v=uUAvXYW5bmI JWST Video (008:06): 1st Month − Launching and Deployment] (update; 2021)
* [https://www.youtube.com/watch?v=QlwatKpla8s JWST Video (003:00): 2nd Month − Mirror Alignment details] (2/11/2022)
* JWST Videos (Mission Control Live) – Deployment Events − Now Successfully Completed (2022):
** [https://www.youtube.com/watch?v=ViXoWdbF-Ys {{small|'''LAUNCH''' (005:07; 25 Dec 2021)}}] ⇒ [https://www.youtube.com/watch?v=dRqHlta6lr8 {{small|'''SEPARATION''' (003:14; 25 Dec 2021)}}] ([https://www.esa.int/ESA_Multimedia/Videos/2021/12/Webb_separation_from_Ariane_5 mirror]) ⇒ [https://www.youtube.com/watch?v=IBPNi7uGgWM James Webb Space Telescope: Sunshield Deployment – Mission Control Live {{small|'''SUNSHIELD''' (152:45; 4 Jan 2022)}}] ⇒
** [https://www.youtube.com/watch?v=-EnlaXnFcGs James Webb Space Telescope: Secondary Mirror Deployment – Mission Control Live {{small|'''SECONDARY MIRROR''' (087:15; 5 Jan 2022)}}] ⇒ [https://www.youtube.com/watch?v=tlGTem8vkB0 James Webb Space Telescope: Primary Mirror Deployment – Mission Control Live {{small|'''PRIMARY MIRROR''' (242:29; 8 Jan 2022)}}] ⇒ [https://www.youtube.com/watch?v=hET2MS1tIjA News Update on James Webb Space Telescope's Full Deployment {{small|'''FINAL DEPLOYMENT''' (085:15; 8 Jan 2022)}}] ⇒
** [https://www.youtube.com/watch?v=VmD8pefGG2k Media Briefing: What's Next for the James Webb Space Telescope {{small|'''ARRIVAL AT L<sub>2</sub>''' (077:14; 24 Jan 2022)}}] ⇒ [https://www.youtube.com/watch?v=DYDNS471jc8 JAMES WEBB TELESCOPE First Photos, Data & Calibrations Explained {{small|'''TESTINGS & CALIBRATIONS'''}}] ⇒ [https://www.youtube.com/watch?v=4Pl749Dgx0A The First Thing That James Webb Will See {{small|'''FIRST LIGHT'''}}]

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