View source for Space debris

{{short description|Pollution around Earth by defunct artificial objects}}
{{redirect|Space Junk|other uses|Space Junk (disambiguation)}}
{{hatnote|"Cosmic debris" redirects here. For the Frank Zappa song, see [[Cosmik Debris]].}}
{{distinguish|Cosmic dust}}
{{Use dmy dates|date=July 2020}}
[[File:Space sustainability urgency in earth orbits black.png|thumb|upright=2|Infographic showing the space debris situation in different kinds of orbits around Earth]]
{{Pollution sidebar|Space pollution}}
'''Space debris''' (also known as '''space junk''', '''space pollution''',<ref name=guardian20170326/> '''space waste''', '''space trash''', '''space garbage''', or '''cosmic debris'''<ref>{{Cite book |url=https://link.springer.com/book/10.1007/978-3-319-51016-3 |title=Cosmic Debris |series=Astronomers' Universe |year=2017 |language=en |doi=10.1007/978-3-319-51016-3|bibcode=2017cdwi.book.....P |isbn=978-3-319-51015-6 |last1=Powell |first1=Jonathan }}</ref><!-- each of these is bolded per [[WP:MOSBOLD]] as redirect targets -->) are defunct human-made objects in space{{snd}}principally in [[Geocentric orbit|Earth orbit]]{{snd}}which no longer serve a useful function. These include [[derelict spacecraft]] (nonfunctional spacecraft and abandoned launch vehicle stages), mission-related debris, and particularly numerous in-Earth orbit, fragmentation debris from the breakup of derelict rocket bodies and spacecraft. In addition to derelict human-made objects left in orbit, space debris includes fragments from disintegration, [[erosion]], or [[collision]]s; solidified liquids expelled from spacecraft; unburned particles from solid rocket motors; and even paint flecks. Space debris represents a risk to spacecraft.<ref>{{cite web |url=http://www.spaceacademy.net.au/watch/debris/debris.htm |title=Guide to Space Debris|website= spaceacademy.net.au |access-date=13 August 2018 |archive-url=https://web.archive.org/web/20180826190550/http://www.spaceacademy.net.au/watch/debris/debris.htm |archive-date=26 August 2018 |url-status=live}}</ref>

Space debris is typically a [[negative externality]]. It creates an external cost on others from the initial action to launch or use a spacecraft in near-Earth orbit, a cost that is typically not taken into account nor fully accounted for<ref name=coase1960>{{cite journal |last=Coase |first=Ronald |author-link=Ronald Coase |title=The Problem of Social Cost |publisher=The University of Chicago Press |url=http://home.cerge-ei.cz/ortmann/UpcesCourse/Coase%20-%20The%20problem%20of%20Social%20Cost.pdf |type=PDF |journal=Journal of Law and Economics |volume=3 |date=October 1960 |pages=1–44 |doi=10.1086/466560 |jstor=724810 |s2cid=222331226 |access-date=13 December 2019 |archive-url=https://web.archive.org/web/20120617034923/http://home.cerge-ei.cz/ortmann/UpcesCourse/Coase%20-%20The%20problem%20of%20Social%20Cost.pdf |archive-date=17 June 2012 |url-status=live}}</ref><ref name="ewot2014">{{cite book |last1=Heyne |first1=Paul |title=The Economic Way of Thinking |last2=Boettke |first2=Peter J. |last3=Prychitko |first3=David L. |publisher=Pearson |year=2014 |isbn=978-0-13-299129-2 |edition=13th |pages=227–228 |language=en-us}}</ref> by the launcher or payload owner.<ref name="muñoz-patchen2019">{{cite journal |title=Regulating the Space Commons: Treating Space Debris as Abandoned Property in Violation of the Outer Space Treaty |journal=Chicago Journal of International Law |last=Muñoz-Patchen |first=Chelsea |publisher=University of Chicago Law School |year=2019 |url=https://cjil.uchicago.edu/publication/regulating-space-commons-treating-space-debris-abandoned-property-violation-outer-space |access-date=13 December 2019 |archive-url=https://web.archive.org/web/20191213230303/https://cjil.uchicago.edu/publication/regulating-space-commons-treating-space-debris-abandoned-property-violation-outer-space |archive-date=13 December 2019 |url-status=live}}</ref><ref name=guardian20170326>{{cite news |url=https://www.theguardian.com/science/2017/mar/26/weve-left-junk-everywhere-why-space-pollution-could-be-humanitys-next-big-problem |title='We've left junk everywhere': why space pollution could be humanity's next big problem |work=The Guardian |date=26 March 2016 |access-date=28 December 2019 |archive-url=https://web.archive.org/web/20191108174731/https://www.theguardian.com/science/2017/mar/26/weve-left-junk-everywhere-why-space-pollution-could-be-humanitys-next-big-problem |archive-date=8 November 2019 |url-status=live}}</ref><ref name=aiaa201804>{{Cite web|url=https://aerospaceamerica.aiaa.org/features/preventing-space-pollution/|title=Preventing space pollution|first=Debra|last=Werner|date= 30 March 2018|publisher=Aerospace America|access-date=January 21, 2023}}</ref>

Several spacecraft, both crewed and un-crewed, have been damaged or destroyed by space debris. The measurement, mitigation, and potential removal of debris is conducted by some participants in the [[space industry]].<ref name="esadebris20190306">{{Cite web |title=Space debris by the numbers |url=https://sdup.esoc.esa.int/discosweb/statistics/ |access-date=2025-04-03 |website=www.esa.int |language=en}}</ref>

{{as of|2025|04}}, the [[European Space Agency]]'s Space Environment statistics reported 40230 artificial objects in orbit above the Earth regularly tracked by Space Surveillance Networks and maintained in their catalogue.<ref name="esadebris20190306">{{Cite web |title=Space debris by the numbers |url=https://sdup.esoc.esa.int/discosweb/statistics/ |access-date=2025-04-03 |website=www.esa.int |language=en}}</ref> 

However, these are just the objects large enough to be tracked and in an orbit that makes tracking possible. Satellite debris that is in a [[Molniya orbit]], such as the Kosmos [[Oko]] series, might be too high above the Northern Hemisphere to be tracked.<ref name="Clark">{{cite book |last=Clark |first=David |title=The Elgar Companion to Development Studies |year=2006 |publisher=Edward Elgar Publishing |isbn=978-1-84376-475-5 |page=668}}</ref> {{as of|January 2019}}, more than 128 million pieces of debris smaller than {{convert|1|cm|abbr=on|sigfig=1}}, about 900,000 pieces of debris 1–10&nbsp;cm, and around 34,000 of pieces larger than {{Convert|10|cm|in|abbr=on}} were estimated to be in orbit around the Earth.<ref name=esadebris20190306/> When the smallest objects of artificial space debris (paint flecks, solid rocket exhaust particles, etc.) are grouped with [[micrometeoroid]]s, they are together sometimes referred to by space agencies as '''MMOD'''<!-- bolded per [[WP:MOSBOLD]] as a redirect target --> (Micrometeoroid and Orbital Debris).

Collisions with debris have become a hazard to spacecraft. The smallest objects cause damage akin to [[sandblasting]], especially to solar panels and optics like telescopes or [[star tracker]]s that cannot easily be protected by a [[hypervelocity ballistic shield|ballistic]] [[Whipple shield|shield]].<ref name="nasa20090428">{{cite web |url= http://images.spaceref.com/news/2009/ODMediaBriefing28Apr09-1.pdf |title= The Threat of Orbital Debris and Protecting NASA Space Assets from Satellite Collisions |date= 2009 |publisher= Space Reference |access-date= 18 December 2012 |archive-url= https://wayback.archive-it.org/all/20151223174746/http://images.spaceref.com/news/2009/ODMediaBriefing28Apr09-1.pdf |archive-date= 23 December 2015 |url-status= live }}</ref>

Below {{convert|2000|km|abbr=on}}, pieces of debris are denser than [[meteoroid]]s. Most are dust from solid rocket motors, surface erosion debris like paint flakes, and frozen coolant from [[RORSAT|Soviet nuclear-powered satellites]].<ref name="wiedemann2009">{{cite journal|first=C. |last=Wiedemann|title=Size distribution of NaK droplets for MASTER-2009|url=https://conference.sdo.esoc.esa.int/proceedings/sdc5/paper/121|journal=Proceedings of the 5th European Conference on Space Debris|date=2 April 2009|volume=672 |page=17 |bibcode=2009ESASP.672E..17W }}</ref><ref name="rossi2009">A. Rossi et al, [https://www.researchgate.net/publication/2353432_EFFECTS_OF_THE_RORSAT_NaK_DROPS_ON_THE_LONG_TERM_EVOLUTION_OF_THE_SPACE_DEBRIS_POPULATION "Effects of the RORSAT NaK Drops on the Long Term Evolution of the Space Debris Population"], University of Pisa, 1997.</ref><ref name="wiedemann2005">
{{Cite journal
| last1 = Wiedemann | first1 = C.
| last2 = Oswald | first2 = M.
| last3 = Stabroth | first3 = S.
| last4 = Klinkrad | first4 = H.
| last5 = Vörsmann | first5 = P.
| title = Size distribution of NaK droplets released during RORSAT reactor core ejection
| doi = 10.1016/j.asr.2005.05.056
| journal = Advances in Space Research
| volume = 35
| issue = 7
| pages = 1290–1295
| year = 2005
| bibcode = 2005AdSpR..35.1290W
}}</ref> For comparison, the [[International Space Station]] (ISS) orbits in the {{convert|300|–|400|km}} range, while the two most recent large debris events, the 2007 [[Government of China|Chinese]] [[2007 Chinese anti-satellite missile test|antisatellite weapon test]] and the [[2009 satellite collision]], occurred at {{convert|800|to|900|km}} altitude.<ref name="nasa9">{{citation |title=The Threat of Orbital Debris and Protecting NASA Space Assets from Satellite Collisions |date=2009 |url=http://images.spaceref.com/news/2009/ODMediaBriefing28Apr09-1.pdf |access-date=18 December 2012 |archive-url=https://wayback.archive-it.org/all/20151223174746/http://images.spaceref.com/news/2009/ODMediaBriefing28Apr09-1.pdf |archive-date=23 December 2015 |url-status=live |publisher=Space Reference}}.</ref> The ISS has [[Whipple shielding]] to resist damage from small MMOD. However, known debris with a collision chance over 1/10,000 are avoided by [[orbital maneuver|maneuvering]] the station.

According to a report published in January 2025, scientists are encouraging vigilance around closing airspace more often to avoid collisions between airline flights and space debris reentering the earth's atmosphere amid an increasing volume of both.<ref>{{Cite web |author1=Leonard David |date=2025-02-03 |title=Falling space debris is a growing worry for aircraft, new research suggests |url=https://www.space.com/space-exploration/launches-spacecraft/falling-space-debris-is-a-growing-worry-for-aircraft-new-research-suggests |access-date=2025-02-03 |website=Space.com |language=en}}</ref> Following a destructive event, the explosion of [[Starship_flight_test_7|SpaceX's Starship Flight 7]] on January 16, 2025, the U.S. Federal Aviation Administration (FAA) slowed air traffic in the area where debris was falling. This prompted several aircraft to request diversion because of low fuel levels while they were holding outside the Debris Response Area.<ref>{{Cite web |author1=Mike Wall |date=2025-01-17 |title=FAA requiring investigation into SpaceX Starship's Flight 7 explosion |url=https://www.space.com/space-exploration/private-spaceflight/faa-requiring-investigation-into-spacex-starships-flight-7-explosion |access-date=2025-02-03 |website=Space.com |language=en-US}}</ref>  

== History ==
[[File:Baker-Nunn camera.jpg|left|upright|thumb|alt=Large camera, with a man standing next to it for scale|[[Schmidt camera#Baker-Nunn|Baker-Nunn cameras]] were widely used to study space debris.]]
Space debris began to accumulate in Earth orbit with the launch of the first [[artificial satellite]], [[Sputnik 1]], into orbit in October, 1957. But even before this event, humans might have produced ejecta that became space debris, as in the August 1957 [[Operation Plumbbob#Pascal-B|Pascal B test]].<ref name="Brownlee, Harrington">{{cite web
| url =https://www.businessinsider.com/fastest-object-robert-brownlee-2016-2?r=US&IR=T#brownlee-wanted-to-measure-how-fast-the-iron-cap-flew-off-the-column-so-he-designed-a-second-experiment-pascal-b-9
| author=Harrington, Rebecca
| date = February 5, 2016
| title = The fastest object ever launched was a manhole cover – here's the story from the guy who shot it into space
| work =[[Business Insider#Divisions|Tech Insider]] – www.businessinsider.com [[Business Insider]]
| accessdate = 11 June 2021}}</ref><ref name="Brownlee, Thomson">{{cite web
| url =https://www.theregister.com/2015/07/16/america_soviets_space_race/
| author= Thomson, Iain
| title = Did speeding American manhole cover beat Sputnik into space? Top boffin speaks to El Reg – How a nuke blast lid may have beaten Soviets by months
|date = 16 July 2015
| work =www.theregister.com
| accessdate = 11 June 2021}}</ref> Going back further, natural [[ejecta]] from Earth has entered orbit.

After the launch of Sputnik, the [[North American Aerospace Defense Command]] (NORAD) began compiling a database (the [[Space Object Catalog]]) of all known rocket launches and objects reaching orbit, including satellites, protective shields and upper-stages of [[launch vehicle]]s. [[NASA]] later published modified versions of the database in [[two-line element set]]s,{{sfn|Hoots|Schumacher|Glover|2004|pp=174–185}} and beginning in the early 1980s, they were republished in the CelesTrak [[bulletin board system]].<ref>{{Cite web |title=CelesTrak: Historical NORAD Two-Line Element Sets |url=http://celestrak.org/NORAD/archives/ |access-date=2024-04-18 |website=celestrak.org}}</ref>

[[File: Gabbard diagram.png|thumb|upright=1.2|alt=Debris graph of altitude and orbital period|Gabbard diagram of almost 300 pieces of debris from the disintegration of the five-month-old third stage of the Chinese Long March 4 booster on 11 March 2000]]
NORAD trackers who fed the database were aware<!-- by when? 1960? 1970? later? --> of other objects in orbit, many of which were the result of in-orbit explosions.<ref name=s48>Schefter, p. 48.</ref> Some were deliberately caused during [[anti-satellite weapon]] (ASAT) testing in the 1960s, and others were the result of rocket stages blowing up in orbit as leftover propellant expanded and ruptured their tanks. More detailed databases and tracking systems were gradually developed, including Gabbard diagrams, to improve the modeling of orbital evolution and decay.<ref>{{cite journal|title=Space Debris and Its Mitigation |first1=Sourabh |last1=Kaushal|first2=Nishant|last2=Arora|url=https://www.spacefuture.com/archive/space_debris_and_its_mitigation.shtml|journal=ISEC Space Elevator Conference|date=August 2010|access-date=November 11, 2022}}</ref><ref name="portree" />

When the NORAD database became publicly available during the 1970s,{{clarify|date=December 2019}} techniques developed for the asteroid-belt were applied to the study{{by whom|date=April 2020}} of known artificial satellite objects.{{citation needed|date=April 2020}}

Time and natural gravitational/atmospheric effects help to clear space debris. A variety of technological approaches have also been proposed, though most have not been implemented. A number of scholars have observed that systemic factors, political, legal, economic, and cultural, are the greatest impediment to the cleanup of near-Earth space. There has been little commercial incentive to reduce space debris since the associated cost does not accrue to the entity producing it. Rather, the cost falls to all users of the space environment who benefit from space technology and knowledge. A number of suggestions for increasing incentives to reduce space debris have been made. These would encourage companies to see the economic benefit of reducing debris more aggressively than existing government mandates require.<ref name=sn20141125>{{cite news |last1=Foust|first1=Jeff |title=Companies Have Technologies, but Not Business Plans, for Orbital Debris Cleanup |url=http://www.spacenews.com/article/civil-space/42656companies-have-technologies-but-not-business-plans-for-orbital-debris |archive-url=https://archive.today/20141206140211/http://www.spacenews.com/article/civil-space/42656companies-have-technologies-but-not-business-plans-for-orbital-debris |url-status=dead |archive-date=6 December 2014 |access-date=28 December 2019 |work=Space News |date=15 November 2014}}</ref> In 1979, NASA founded the [[NASA Orbital Debris Program Office|Orbital Debris Program]] to research mitigation measures for space debris in Earth orbit.<ref name=nasa20161103>{{cite web |url=https://orbitaldebris.jsc.nasa.gov/ |title=NASA Orbital Debris Program |access-date=10 October 2016 |archive-url=https://web.archive.org/web/20161103215654/https://www.orbitaldebris.jsc.nasa.gov/ |archive-date=3 November 2016 |url-status=live}}</ref><ref>{{cite web|title=Space Debris|url=https://www.nasa.gov/centers/hq/library/find/bibliographies/space_debris|date=Jul 1, 2019|publisher=NASA|access-date=December 4, 2022}}</ref>

=== Debris growth ===
[[File:Debris-GEO1280.jpg|thumb|NASA computer-generated image of debris objects in Earth orbit, c. 2005]]
During the 1980s, NASA and other U.S. groups attempted to limit the growth of debris. One trial solution was implemented by [[McDonnell Douglas]] in 1981 for the [[Delta (rocket family)|Delta launch vehicle]] by having the booster move away from its payload and vent any propellant remaining in its tanks.<ref>{{cite web |last=Jessica |date=21 July 2017 |title=SMA Valves to Prevent In-Orbit Explosions |url=https://blogs.esa.int/cleanspace/2017/07/21/sma-valves-to-prevent-in-orbit-explosions/ |access-date=21 January 2023 |publisher=[[European Space Agency]] |type=Blog posting |quote=Delta upper stage: There were several events for Delta second stages due to residual propellants until depletion burns were introduced in 1981.}}</ref> This eliminated one source for pressure buildup in the tanks which had previously caused them to explode and create additional orbital debris.{{sfn|Schefter|1982|p=50}} Other countries were slower to adopt this measure and, due especially to a number of launches by the [[Soviet Union]], the problem grew throughout the decade.<ref name="h7">See charts, Hoffman, p. 7.</ref>

A new battery of studies followed as NASA, NORAD, and others attempted to better understand the orbital environment, with each adjusting the number of pieces of debris in the critical-mass zone upward. Although in 1981 (when Schefter's article was published) the number of objects was estimated at 5,000,<ref name=s48 /> new detectors in the [[Ground-based Electro-Optical Deep Space Surveillance]] system found new objects. By the late 1990s, it was thought that most of the 28,000 launched objects had already decayed and about 8,500 remained in orbit.<ref>See chart, Hoffman p. 4.</ref> By 2005 this was adjusted upward to 13,000 objects,<ref>In the time between the writing of Klinkrad (2006) Chapter 1 (earlier) and the Prolog (later) of ''Space Debris'', Klinkrad changed the number from 8,500 to 13,000 – compare pp. 6 and ix.</ref> and a 2006 study increased the number to 19,000 as a result of an ASAT and a satellite collision.<ref>Michael Hoffman, [https://archive.today/20120707143803/http://defensenews.com/blogs/space-symposium/ "It's getting crowded up there."] ''Space News'', 3 April 2009.</ref> In 2011, NASA said that 22,000 objects were being tracked.<ref>[https://www.foxnews.com/science/space-junk-threat-will-grow-for-astronauts-and-satellites "Space Junk Threat Will Grow for Astronauts and Satellites"], Fox News, 6 April 2011.</ref>

A 2006 NASA model suggested that if no new launches took place, the environment would retain the then-known population until about 2055, when it would increase on its own.<ref name=natgeo>Stefan Lovgren, [http://news.nationalgeographic.com/news/2006/01/0119_060119_space_junk.html "Space Junk Cleanup Needed, NASA Experts Warn."] {{Webarchive|url=https://web.archive.org/web/20090907084422/http://news.nationalgeographic.com/news/2006/01/0119_060119_space_junk.html |date=7 September 2009}} ''National Geographic News'', 19 January 2006.</ref><ref>J.-C Liou and N. L. Johnson, [http://www.sciencemag.org/cgi/content/short/311/5759/340 "Risks in Space from Orbiting Debris"]
{{Webarchive|url=https://web.archive.org/web/20080601031610/http://www.sciencemag.org/cgi/content/short/311/5759/340 |date=1 June 2008}}, ''Science'', Volume 311 Number 5759 (20 January 2006), pp. 340–341</ref> Richard Crowther of Britain's [[Defence Evaluation and Research Agency]] said in 2002 that he believed the cascade would begin about 2015.<ref>Antony Milne, ''Sky Static: The Space Debris Crisis'', Greenwood Publishing Group, 2002, {{ISBN|0-275-97749-8}}, p. 86.</ref> The National Academy of Sciences, summarizing the professional view, noted widespread agreement that two bands of LEO space{{snd}}900 to {{convert|1000|km|abbr=on}} and {{convert|1500|km|abbr=on}}{{snd}}were already past critical density.{{sfn|Gleghorn|1995|p=7}}

In the 2009 [[Council of European Aerospace Societies|CEAS]] European Air and Space Conference, [[University of Southampton]] researcher Hugh Lewis predicted that the threat from space debris would rise 50 percent in the next decade and quadruple in the next 50 years. {{as of|2009}}, more than 13,000 close calls were tracked weekly.<ref>{{Cite web |last=Marks |first=Paul |date=October 27, 2009 |title=Space debris threat to future launches |url=https://www.newscientist.com/article/dn18050-space-debris-threat-to-future-launches/ |access-date=2024-04-18 |website=New Scientist |language=en-US}}</ref>

A 2011 report by the [[National Research Council (United States)|U.S. National Research Council]] warned NASA that the amount of orbiting space debris was at a critical level. According to some computer models, the amount of space debris "has reached a tipping point, with enough currently in orbit to continually collide and create even more debris, raising the risk of spacecraft failures." The report called for international regulations limiting debris and research of disposal methods.<ref>{{Cite news |date=2011-09-02 |title=Space junk at tipping point, says report |url=https://www.bbc.com/news/world-us-canada-14757926 |access-date=2024-04-18 |work=BBC News |language=en-GB}}</ref>

[[File:LEO-SpaceDebris-Nov2020.png|right|thumb|upright=1.6|alt=Objects in Earth orbit including fragmentation debris. November 2020 NASA:ODPO|Objects in Earth orbit including fragmentation debris, November 2020, NASA: ODPO]]

==== Debris history in particular years ====
<!-- starting to collect some data, and sources, that could be the beginnings of a table... and perhaps graphs. --><!-- the data in four of the bullets added below on 25 Dec 2019 were, currently or formerly, in the article lede; so that was a convenient place to locate a few data points and sources for the historical data -->
* By mid-1994 there had been 68 breakups or debris "anomalous events" involving satellites launched by the former Soviet Union/Russia and 18 similar events had been discovered involving rocket bodies and other propulsion-related operational debris.<ref name="soviet"/>
*{{as of|2009}}, 19,000 debris over {{convert|5|cm|abbr=on|sigfig=1}} were tracked by the [[United States Space Surveillance Network]].<ref name=nasa9 />
*{{as of|July 2013}}, estimates of more than 170 million debris smaller than {{convert|1|cm|abbr=on|sigfig=1}}, about 670,000 debris 1–10&nbsp;cm, and approximately 29,000 larger pieces of debris were in orbit.<ref name="esadebris2013">[http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/How_many_space_debris_objects_are_currently_in_orbit "How many space debris objects are currently in orbit?"] {{Webarchive|url=https://web.archive.org/web/20160518045818/http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/How_many_space_debris_objects_are_currently_in_orbit|date=18 May 2016}} ''ESA'', July 2013. Retrieved 6 February 2016.</ref>
*{{as of|2016|7}}, nearly 18,000 artificial objects were orbiting above Earth,<ref name=ODQN-201607>{{cite newsletter |url=https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv20i3.pdf |title=Satellite Box ScoreS|work=Orbital Debris Quarterly News |volume=20 |issue=3 |page=8 |publisher=[[NASA]] |date=July 2016 |access-date=10 October 2016 |archive-url=https://web.archive.org/web/20161011055108/https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv20i3.pdf |archive-date=11 October 2016 |url-status=live}}</ref> including 1,419 operational satellites.<ref name=ucs20160811>{{cite web |title=UCS Satellite Database |date=11 August 2016 |work=Nuclear Weapons & Global Security |publisher=[[Union of Concerned Scientists]] |url=http://www.ucsusa.org/nuclear_weapons_and_global_security/space_weapons/technical_issues/ucs-satellite-database.html |access-date=10 October 2016 |archive-url=https://web.archive.org/web/20100603022505/http://www.ucsusa.org/nuclear_weapons_and_global_security/space_weapons/technical_issues/ucs-satellite-database.html |archive-date=3 June 2010 |url-status=live}}</ref>
*{{as of|2019|10}}, nearly 20,000 artificial objects were in orbit above the Earth,<ref name="ODQN-201911">{{cite newsletter |date=November 2022 |title=Satellite Box Score |url=https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv26i4.pdf |url-status=live |work=Orbital Debris Quarterly News |publisher=[[NASA]] |volume=26 |issue=4 |page=14 |archive-url=https://web.archive.org/web/20191224131630/https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv23i4.pdf |archive-date=24 December 2019 |access-date=24 December 2019}}</ref> including 2,218 operational satellites.<ref name="ucs20191216">{{cite web |date=May 1, 2022 |title=UCS Satellite Database |url=https://www.ucsusa.org/resources/satellite-database |url-status=live |archive-url=https://web.archive.org/web/20191220002901/https://ucsusa.org/resources/satellite-database |archive-date=20 December 2019 |access-date=24 December 2019 |work=Nuclear Weapons & Global Security |publisher=[[Union of Concerned Scientists]]}}</ref><!-- there are other random historical numbers, from various sources, explicated in the prose throughout the article; e.g., 2005, 2000, etc. -->

== Characterization ==

=== {{anchor|Large vs. small}}Size and numbers===
{{as of |January 2019}} there were estimated to be over 128 million pieces of debris smaller than {{convert|1|cm|abbr=on}}, and approximately 900,000 pieces between 1 and 10&nbsp;cm. The count of large debris (defined as 10&nbsp;cm across or larger<ref name="untechreport1999">{{cite book |url=https://www.orbitaldebris.jsc.nasa.gov/library/un_report_on_space_debris99.pdf |title=Technical report on space debris |year=1999 |publisher=United Nations |isbn=978-92-1-100813-5 |via=[[NASA]] |archive-url=https://web.archive.org/web/20090724134642/http://www.orbitaldebris.jsc.nasa.gov/library/UN_Report_on_Space_Debris99.pdf |archive-date=24 July 2009|url-status=live}}</ref>) was 34,000 in 2019,<ref name="esadebris20190306" /> and at least 37,000 by June 2023.<ref name=alderson2023/> The technical measurement cut-off{{clarify|this term has not been defined; also would need the time frame clarified in the prose as technology and technical capabilities frequently change|date=December 2019}} is c. {{convert|3|mm|abbr=on}}.<ref name="nasadebris2012">[http://orbitaldebris.jsc.nasa.gov/faqs.html#3 "Orbital Debris FAQ: How much orbital debris is currently in Earth orbit?"] {{Webarchive|url=https://web.archive.org/web/20090825064237/http://orbitaldebris.jsc.nasa.gov/faqs.html#3|date=25 August 2009}} ''NASA'', March 2012. Retrieved 31 January 2016.</ref>

{{as of|2020}}, there were 8,000 metric tons of debris in orbit, a figure that is expected to increase.{{sfn|Liou|2020}}

=== {{anchor|Debris in LEO}}Low Earth orbit ===
[[File:Objects and debris in LEO by height black.png|thumb|upright=2|Debris density in low Earth orbit]]
In the orbits nearest to Earth{{snd}}less than {{cvt|2000|km}} [[orbital altitude]], referred to as low-Earth orbit (LEO){{snd}}there have traditionally been few "universal orbits" that keep a number of spacecraft in particular rings (in contrast to [[Geosynchronous orbit|GEO]], a single orbit that is widely used by [[List of satellites in geosynchronous orbit|over 500 satellites]]). There is currently 85% pollution in LEO (Low Earth Orbit). This was beginning to change in 2019, and several companies began to deploy the early phases of [[satellite internet constellation]]s, which will have many universal orbits in LEO with 30 to 50 satellites per orbital plane and altitude. Traditionally, the most populated LEO orbits have been a number of [[Sun-synchronous orbit|Sun-synchronous satellites]] that keep a constant angle between the Sun and the [[Orbital plane (astronomy)|orbital plane]], making Earth observation easier with consistent sun angle and lighting. Sun-synchronous orbits are [[Polar orbit|polar]], meaning they cross over the polar regions. LEO satellites orbit in many planes, typically up to 15 times a day, causing frequent approaches between objects. The density of satellites{{snd}}both active and derelict{{snd}}is much higher in LEO.<ref name="ars200902">{{Cite web |last=Ford |first=Matt |date=2009-02-27 |title=Orbiting space junk heightens risk of satellite catastrophes |url=https://arstechnica.com/science/2009/02/orbiting-space-junk-heightens-risk-of-satellite-catastrophes/ |access-date=2024-04-18 |website=Ars Technica |language=en-us}}</ref>

Orbits are affected by [[Perturbation (astronomy)|gravitational perturbations]] (which in LEO include unevenness of the Earth's gravitational field due to variations in the density of the planet), and collisions can occur from any direction. The average impact speed of collisions in Low Earth Orbit is 10&nbsp;km/s with maximums reaching above 14&nbsp;km/s due to [[orbital eccentricity]].<ref>{{cite book |last1=Wertz |first1=James |title=Space mission engineering: the new SMAD |last2=Everett |first2=David |last3=Puschell |first3=Jeffrey |date=2011 |publisher=Microcosm Press |isbn=978-1881883159 |location=Hawthorne, California |page=139 |language=en-us}}</ref> The [[2009 satellite collision]] occurred at a closing speed of {{Convert|11.7|km/s|mph|abbr=on}},<ref name="esa20110809">{{Cite web |date=February 19, 2009 |title=European Space Agency |url=https://www.esa.int/ |access-date=2024-04-18 |website=www.esa.int |language=en}}</ref> creating over 2,000 large debris fragments.<ref name=nasa201107>{{cite web|title=Orbital Debris Quarterly News, July 2011 |publisher=NASA Orbital Debris Program Office |url=http://orbitaldebris.jsc.nasa.gov/newsletter/pdfs/ODQNv15i3.pdf |access-date=1 January 2012 |url-status=dead |archive-url=https://web.archive.org/web/20111020092342/http://orbitaldebris.jsc.nasa.gov/newsletter/pdfs/ODQNv15i3.pdf |archive-date=20 October 2011}}</ref> These debris cross many other orbits and increase debris collision risk.

It is theorized that a sufficiently large collision of spacecraft could potentially lead to a cascade effect, or even make some particular [[low Earth orbit]]s effectively unusable for long term use by orbiting satellites<!-- Kessler syndrome renders particular low-Earth orbits unusable, not impassable. Space debris in LEO is chiefly a danger to craft that ''remain'' in LEO for extended periods. Spacecraft that ''cross'' LEO en route to a higher orbit spend very little time at the altitude of LEO, and therefore would face a correspondingly low risk. -->, a phenomenon known as the [[Kessler syndrome]].<ref name="k09">{{cite web |author=Kessler |first=Donald J. |date=8 March 2009 |title=The Kessler Syndrome |url=http://webpages.charter.net/dkessler/files/KesSym.html |url-status=dead |archive-url=https://web.archive.org/web/20100527195029/http://webpages.charter.net/dkessler/files/KesSym.html |archive-date=27 May 2010 |access-date=22 September 2009}}</ref> The theoretical effect is projected to be a theoretical runaway [[chain reaction]] of collisions that could occur, exponentially increasing the number and density of space debris in low-Earth orbit, and has been hypothesized to ensue beyond some critical density.<ref name=wired20140222>Lisa Grossman, [https://www.wired.com/wiredscience/tag/kessler-syndrome/ "NASA Considers Shooting Space Junk with Lasers"] {{Webarchive|url=https://web.archive.org/web/20140222110801/http://www.wired.com/wiredscience/tag/kessler-syndrome/ |date=22 February 2014}}, ''wired'', 15 March 2011.</ref>

Crewed space missions are mostly at {{convert|400|km|abbr=on}} altitude and below, where air drag helps clear zones of fragments. The [[Atmosphere of Earth|upper atmosphere]] is not a fixed density at any particular orbital altitude; it varies as a result of [[atmospheric tide]]s and expands or contracts over longer time periods as a result of [[space weather]].<ref>{{Cite journal|last1=Nwankwo|first1=Victor U. J|last2=Denig|first2=William|last3=Chakrabarti|first3=Sandip K.|last4=Ajakaiye|first4=Muyiwa P.|last5=Fatokun|first5=Johnson|last6=Akanni|first6=Adeniyi W.|last7=Raulin|first7=Jean-Pierre|last8=Correia|first8=Emilia|last9=Enoh|first9=John E.|date=2020-09-15|title=Atmospheric drag effects on modelled LEO satellites during the July 2000 Bastille Day event in contrast to an interval of geomagnetically quiet conditions|journal=[[Annales Geophysicae]]|doi=10.5194/angeo-2020-33-rc2|doi-access=free}}</ref> These longer-term effects can increase drag at lower altitudes; the 1990s expansion was a factor in reduced debris density.{{sfn|Kessler|1991|p=65}} Another factor was fewer launches by Russia; the [[Soviet space program|Soviet Union]] made most of their launches in the 1970s and 1980s.<ref name="klinkrad2006">{{cite book |author=Klinkrad |first=Heiner |url=http://www.praxis-publishing.co.uk/9783540254485.htm |title=Space Debris: Models and Risk Analysis |publisher=Springer-Praxis |year=2006 |isbn=3-540-25448-X |access-date=20 December 2009 |archive-url=https://web.archive.org/web/20110512174448/http://www.praxis-publishing.co.uk/9783540254485.htm |archive-date=12 May 2011 |url-status=live}}</ref>{{rp|7}}

=== {{anchor|Debris at higher altitudes}}Higher altitudes ===
[[File:Satellite break-up ESA375611.jpg|thumb|Illustration of a satellite breaking up into multiple pieces at higher altitudes]]
At higher altitudes, where air drag is less significant, orbital decay takes longer. Slight [[Drag (physics)|atmospheric drag]], [[Lunar theory|lunar perturbations]], Earth's gravity perturbations, [[solar wind]], and solar [[radiation pressure]] can gradually bring debris down to lower altitudes (where it decays), but at very high altitudes this may take centuries.<ref>{{cite web|title=How Satellites Work|first1=Gary |last1=Brown |first2=William |last2=Harris|date=19 May 2000 |url=https://science.howstuffworks.com/satellite6.htm|publisher=HowStuffWorks.com|access-date=21 January 2023}}</ref> Although high-altitude orbits are less commonly used than LEO and the onset of the problem is slower, the numbers progress toward the critical threshold more quickly.{{contradictory inline|date=December 2015}}{{page needed|date=December 2015}}<ref>{{Cite journal| bibcode=2005ESASP.587..113S | title=Optical observation of space debris in high-altitude orbits | journal=Proceedings of the 4th European Conference on Space Debris (ESA SP-587). 18–20 April 2005 | volume=587 | page=113 | last1=Schildknecht | first1=T. |last2=Musci | first2=R. | last3=Flury | first3=W. | last4=Kuusela | first4=J. | last5=De Leon | first5=J. | last6=Dominguez Palmero | first6=L. De Fatima |year=2005}}</ref>

Many communications satellites are in [[geostationary orbit]]s (GEO), clustering over specific targets and sharing the same orbital path. Although velocities are low between GEO objects, when a satellite becomes derelict (such as [[Telstar 401]]) it assumes a geosynchronous orbit; its [[orbital inclination]] increases about 0.8° and its speed increases about {{convert|160|km/h|mph|abbr=on}} per year. Impact velocity peaks at about {{convert|1.5|km/s|abbr=on}}. [[Perturbation (astronomy)|Orbital perturbations]] cause longitude drift of the inoperable spacecraft and [[precession]] of the orbital plane. Close approaches (within 50 meters) are estimated at one per year.<ref>[https://web.archive.org/web/20110718231404/http://www.weblab.dlr.de/rbrt/pdf/ISSFD_89085.pdf "Colocation Strategy and Collision Avoidance for the Geostationary Satellites at 19 Degrees West."] ''CNES Symposium on Space Dynamics'', 6–10 November 1989.</ref> The collision debris pose less short-term risk than from a LEO collision, but the satellite would likely become inoperable. Large objects, such as [[Space-based solar power|solar-power satellites]], are especially vulnerable to collisions.<ref>{{cite journal | last1 = van der Ha | first1 = J. C. | last2 = Hechler | first2 = M. | year = 1981| title = The Collision Probability of Geostationary Satellites | journal = 32nd International Astronautical Congress | volume = 1981 | page = 23 | bibcode=1981rome.iafcR....V}}</ref>

Although the [[International Telecommunication Union|ITU]] now requires proof a satellite can be moved out of its orbital slot at the end of its lifespan, studies suggest this is insufficient.<ref name= Anselmo>{{cite journal | last1 = Anselmo | first1 = L. |last2=Pardini |first2=C. | year = 2000 |title=Collision Risk Mitigation in Geostationary Orbit | journal = Space Debris | volume = 2 | issue = 2| pages = 67–82 | doi = 10.1023/A:1021255523174| bibcode = 2000SpDeb...2...67A | s2cid = 118902351 }}</ref> Since GEO orbit is too distant to accurately measure objects under {{convert|1|m|abbr=on}}, the nature of the problem is not well known.{{sfn|Gleghorn|1995|p=86}} Satellites could be moved to empty spots in GEO, requiring less maneuvering and making it easier to predict future motion.{{sfn|Gleghorn|1995|p=152}} Satellites or boosters in other orbits, especially stranded in [[geostationary transfer orbit]], are an additional concern due to their typically high crossing velocity.

Despite efforts to reduce risk, spacecraft collisions have occurred. The [[European Space Agency]] telecom satellite [[Olympus-1]] was struck by a [[meteoroid]] on 11 August 1993 and eventually moved to a [[graveyard orbit]].<ref name="The Olympus failure">[http://www.selkirkshire.demon.co.uk/analoguesat/olympuspr.html "The Olympus failure"] ''ESA press release'', 26 August 1993. {{webarchive|url=https://web.archive.org/web/20070911181644/http://www.selkirkshire.demon.co.uk/analoguesat/olympuspr.html|date=11 September 2007}}.</ref> On 29 March 2006, the Russian [[Express (satellite)|Express-AM11]] communications satellite was struck by an unknown object and rendered inoperable;<ref name=srdc20060419>[https://archive.today/20130104185122/http://www.spaceref.com/news/viewsr.html?pid=20320 "Notification for Express-AM11 satellite users in connection with the spacecraft failure"] ''Russian Satellite Communications Company'', 19 April 2006.</ref> its engineers had enough contact time with the satellite to send it into a graveyard orbit.

== {{anchor|Sources of debris}}Sources ==

=== Dead spacecraft ===
{{main category|Derelict satellites orbiting Earth}}
{{main category|Spacecraft that broke apart in space}}
[[File:Vanguard 1.jpg|thumb|alt=Small, round satellite with six rod antennas radiating from it|[[Vanguard 1]] is expected to remain in orbit for 240 years.<ref>{{cite web |title=Vanguard 1 |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1958-002B |access-date=4 October 2019 |archive-url=https://web.archive.org/web/20190815201608/https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1958-002B |archive-date=15 August 2019 |url-status=live}}</ref><ref>{{cite web |url=http://www.eurekalert.org/pub_releases/2008-03/nrl-vic031308.php |title=Vanguard I celebrates 50 years in space |publisher=Eurekalert.org |access-date=2013-10-04 |archive-url=https://web.archive.org/web/20130605153254/http://www.eurekalert.org/pub_releases/2008-03/nrl-vic031308.php |archive-date=5 June 2013 |url-status=live}}</ref>]]

In 1958, the United States of America launched [[Vanguard I]] into a [[medium Earth orbit]] (MEO). {{As of|2009|10}}, it, the upper stage of Vanguard 1's launch rocket and associated piece of debris, are the oldest surviving artificial space objects still in orbit and are expected to be until after the year 2250.{{sfn|Johnson|1998|p=62}}<ref>{{Cite web |url=http://www.eurekalert.org/pub_releases/2008-03/nrl-vic031308.php |title=Vanguard 50 years |access-date=4 October 2013 |archive-url=https://web.archive.org/web/20130605153254/http://www.eurekalert.org/pub_releases/2008-03/nrl-vic031308.php |archive-date=5 June 2013 |url-status=live}}</ref> {{As of|2022|5}}, the [[Union of Concerned Scientists]] listed 5,465 operational satellites from a known population of 27,000 pieces of orbital debris tracked by NORAD.<ref>{{cite web |title=UCS Satellite Database |url=https://www.ucsusa.org/resources/satellite-database |access-date=17 January 2023}}</ref><ref>{{cite web |last1= |date=13 April 2015 |title=Space Debris and Human Spacecraft |url=https://www.nasa.gov/mission_pages/station/news/orbital_debris.html |access-date=17 January 2023 |website=NASA.gov}}</ref>

Occasionally satellites are left in orbit when they're no longer useful. Many countries require that satellites go through [[Passivation (spacecraft)|passivation]] at the end of their life. The satellites are then either boosted into a higher, [[graveyard orbit]] or a lower, short-term orbit. Nonetheless, satellites that have been properly moved to a higher orbit have an eight-percent probability of puncture and coolant release over a 50-year period. The coolant freezes into droplets of solid sodium-potassium alloy, creating more debris.<ref name=wiedemann2009/><ref name=rossi1997>A. Rossi et al, [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.27.8466&rep=rep1&type=pdf "Effects of the RORSAT NaK Drops on the Long Term Evolution of the Space Debris Population"]{{cbignore|bot=medic}}, University of Pisa, 1997.</ref>

Despite the use of passivation, or prior to its standardization, many satellites and rocket bodies have exploded or broken apart on orbit. In February 2015, for example, the [[USAF]] [[Defense Meteorological Satellite Program]] Flight 13 (DMSP-F13) exploded on orbit, creating at least 149 debris objects, which were expected to remain in orbit for decades.<ref name=sn20150506>{{cite news |last1=Gruss|first1=Mike |title=DMSP-F13 Debris To Stay on Orbit for Decades |url=http://spacenews.com/dmsp-f13-debris-to-stay-on-orbit-for-decades/ |access-date=7 May 2015 |work=Space News |date=2015-05-06}}</ref> Later that same year, [[NOAA-16]] which had been decommissioned after an anomaly in June 2014, broke apart on orbit into at least 275 pieces.<ref name=keiso-20160326>{{cite tweet|author=T.S. Kelso, CelesTrak |user=TSKelso|number=713665017225281536|title=That brings the total so far for the NOAA 16 debris event to 275 pieces, with none having decayed from orbit|date=March 26, 2016|access-date=March 28, 2016}}</ref> For older programs, such as the Soviet-era [[Meteor (satellite)#Meteor-2|Meteor 2]] and [[Kosmos (satellite)|Kosmos]] satellites, design flaws resulted in numerous break-ups{{snd}}at least 68 by 1994{{snd}}following decommissioning, resulting in more debris.<ref name="soviet">{{cite web |last1=Clark |first1=Phillip |title=Space Debris Incidents Involving Soviet/Russian Launches |url=http://www.friends-partners.org/oldfriends/jgreen/bispaper.html |archive-url=https://web.archive.org/web/20211025015944/http://www.friends-partners.org/oldfriends/jgreen/bispaper.html |access-date=7 February 2023|archive-date=25 October 2021 }}</ref>

In addition to the accidental creation of debris, some has been made intentionally through the deliberate destruction of satellites. This has been done as a test of anti-satellite or anti-ballistic missile technology, or to prevent a sensitive satellite from being examined by a foreign power.<ref name="soviet"/> The [[United States]] has conducted over 30 [[Anti-satellite weapon|anti-satellite weapons tests]] (ASATs), the [[Soviet Union]]/[[Russia]] has performed at least 27, [[China]] has performed 10 and [[India]] has performed at least one.<ref>{{cite web |last=George |first=Justin Paul |date=March 27, 2019 |title=History of anti-satellite weapons: US tested 1st ASAT missile 60 years ago |url=https://www.theweek.in/news/sci-tech/2019/03/27/history-anti-satellite-weapon-us-asat-missile.html |access-date=January 21, 2023 |publisher=This Week |quote=Russia: 20 co-orbital tests, 7 ground/air launched tests.}}</ref><ref name="indiatest">{{citation |last=Tellis |first=Ashley J. |title=India's ASAT Test: An Incomplete Success |date=April 15, 2019 |url=https://carnegieendowment.org/research/2019/04/indias-asat-test-an-incomplete-success?lang=en |access-date=January 21, 2023 |publisher=Carnegie Endowment for International Space}}.</ref> The most recent ASATs were the Chinese [[2007 Chinese anti-satellite missile test|interception of FY-1C]], Russian trials of its [[PL-19 Nudol]], the American [[Operation Burnt Frost|interception of USA-193]] and India's [[2019 Indian anti-satellite missile test|interception of an unstated live satellite]].<ref name="indiatest"/>

=== Lost equipment ===
[[File:Black_Knight_Satellite_(cropped).jpg|thumb|A drifting [[Space blanket|thermal blanket]] photographed in 1998 during [[STS-88]]]]
Space debris includes a glove lost by astronaut [[Ed White (astronaut)|Ed White]] on the first American [[Extra-vehicular activity|space-walk]] (EVA), a camera lost by [[Michael Collins (astronaut)|Michael Collins]] near [[Gemini 10]], a thermal blanket lost during STS-88, garbage bags jettisoned by Soviet [[cosmonauts]] during [[Mir]]'s 15-year life,{{sfn|Johnson|1998|p=63}} a wrench, and a toothbrush.<ref>{{Citation |last=Tufte |first=Edward R. |title=Envisioning Information |page=48 |year=2013 |url=https://archive.org/details/envisioninginfor0000tuft |place=Cheshire, Connecticut |publisher=Graphics Press |isbn=978-0-9613921-1-6 |url-access=registration |orig-year=1990}}.</ref> [[Sunita Williams]] of [[STS-116]] lost a camera during an EVA. During an [[STS-120]] EVA to reinforce a torn solar panel, a pair of pliers was lost, and in an [[STS-126]] EVA, [[Heidemarie Stefanyshyn-Piper]] lost a briefcase-sized tool bag.<ref>Photo of tool bag floating near ISS [[:File:Bye tool bag.jpg|Image on Wikipedia]].</ref>

=== Boosters ===
{{main category|Spacecraft that broke apart in space}}
[[File:Delta-II Stage2 XSS-10.jpg|thumb|Spent upper stage of a [[Delta II]] rocket, photographed by the [[XSS 10]] satellite]]
A significant portion of debris is due to rocket upper stages (e.g. the [[Inertial Upper Stage]]) breaking up due to decomposition of [[Passivation (spacecraft)|unvented]] fuel.<ref name=loftus1989>{{cite book |last=Loftus|first=Joseph P. |title=Orbital Debris from Upper-stage Breakup |year=1989 |publisher=AIAA |page=227 |url=https://books.google.com/books?id=RehH7b_kmNEC |isbn=978-1-60086-376-9}}</ref> The first such instance involved the launch of the [[Transit (satellite)|Transit-4a]] satellite in 1961. Two hours after insertion, the [[Thor-Ablestar|Ablestar]] upper stage exploded. Even boosters that don't break apart can be a problem. A major known impact event involved an (intact) [[Ariane (rocket family)|Ariane]] booster.<ref name=klinkrad2006/>{{rp|2}}

Although NASA and the [[United States Air Force]] now require upper-stage passivation, other launchers{{snd}}such as the Chinese and Russian space agencies{{snd}}do not. Lower stages, like the Space Shuttle's [[solid rocket booster]]s or the [[Apollo program]]'s [[Saturn IB]] launch vehicles, do not reach orbit.<ref>Some return to Earth intact, see [http://www.reentrynews.com/recovered.html this list] {{webarchive|url=https://web.archive.org/web/20091028021045/http://www.reentrynews.com/recovered.html |date=28 October 2009}} for examples.</ref>

Examples:

* Two Japanese H-2A rockets broke up in 2006.<ref name="newscientist.com">[https://www.newscientist.com/article/dn10979-spate-of-rocket-breakups-creates-new-space-junk.html "Spate of rocket breakups creates new space junk"] {{Webarchive|url=https://web.archive.org/web/20140814170549/http://www.newscientist.com/article/dn10979-spate-of-rocket-breakups-creates-new-space-junk.html |date=14 August 2014}}, ''NewScientist'', 17 January 2007. Retrieved 16 March 2007.</ref>
* A Russian [[Briz-M]] booster stage exploded in orbit over South Australia on 19 February 2007. Launched on 28 February 2006 carrying an [[Arabsat-4A]] [[communications satellite]], it malfunctioned before it could use up its propellant. Although the explosion was captured on film by astronomers, due to the orbit path the debris cloud has been difficult to measure with radar. By 21 February 2007, over 1,000 fragments were identified.<ref>[http://www.spaceweather.com/archive.php?view=1&day=21&month=02&year=2007 "Rocket Explosion"] {{Webarchive|url=https://web.archive.org/web/20080130083829/http://www.spaceweather.com/archive.php?view=1&day=21&month=02&year=2007 |date=30 January 2008}}, Spaceweather.com, 22 February 2007. Retrieved 21 February 2007.</ref><ref>Ker Than, [http://www.space.com/news/070221_rocket_explodes.html "Rocket Explodes Over Australia, Showers Space with Debris"] {{Webarchive|url=https://web.archive.org/web/20080724133027/http://www.space.com/news/070221_rocket_explodes.html |date=24 July 2008}} ''Space.com'', 21 February 2007. Retrieved 21 February 2007.</ref> A 14 February 2007 breakup was recorded by Celestrak.<ref>[http://celestrak.com/events/debris-events.asp "Recent Debris Events"] {{Webarchive|url=https://web.archive.org/web/20070320125625/http://www.celestrak.com/events/debris-events.asp |date=20 March 2007}} ''celestrak.com'', 16 March 2007. Retrieved 14 July 2001.</ref>
* Another Briz-M broke up on 16 October 2012 after a failed 6 August [[Proton-M]] launch. The amount and size of the debris was unknown.<ref>{{cite web |url=http://www.zarya.info/Gallimaufry/120707ProtonFailure.php |title=Proton Launch Failure 2012 Aug 6 |date=21 October 2012 |access-date=21 October 2012 |publisher=Zarya |url-status=dead |archive-url=https://web.archive.org/web/20121010150558/http://www.zarya.info/Gallimaufry/120707ProtonFailure.php |archive-date=10 October 2012}}</ref>
*The second stage of the [[Zenit-2]], called the SL-16 by western governments, along with the second stages of the [[Vostok (rocket family)|Vostok]] and [[Kosmos (rocket family)|Kosmos]] launch vehicles, make up about 20% of the total mass of launch debris in Low Earth Orbit (LEO).<ref>{{cite journal |last1=Liou |first1=J-C |title=An Update on LEO Environment Remediation with Active Debris Removal |journal=Orbital Debris Quarterly News |date=April 2011 |volume=15 |issue=2 |page=5 |url=https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv15i2.pdf |access-date=12 December 2022}}</ref> An analysis that determined the 50 "statistically most concerning" debris objects in low Earth orbit determined that the top 20 were all Zenit-2 upper stages.<ref>{{cite web |last1=Foust |first1=Jeff |title=Upper stages top list of most dangerous space debris |url=https://spacenews.com/upper-stages-top-list-of-most-dangerous-space-debris/ |website=[[Space News]]|date=13 October 2020 |access-date=12 December 2022}}</ref>
*a Delta II rocket used to launch NASA's 1989 COBE spacecraft exploded on December 3, 2006. This occurred even though its residual fuel had already been vented to space.<ref name="newscientist.com"/>
*In 2018–2019, three different [[Atlas V]] [[Centaur (rocket stage)|Centaur]] second stages broke up.<ref>{{cite web |url=http://iaaweb.org/iaa/Scientific%20Activity/debrisminutes09184.pdf |title=Major fragmentation of Atlas 5 Centaur upper stage 2014-055B (SSN #40209) |access-date=22 May 2019 |archive-date=19 August 2019 |archive-url=https://web.archive.org/web/20190819102532/http://iaaweb.org/iaa/Scientific%20Activity/debrisminutes09184.pdf |url-status=dead }}</ref><ref>{{cite web |url=http://www.esa.int/Our_Activities/Space_Safety/Rocket_break-up_provides_rare_chance_to_test_debris_formation |title=Rocket break up provides rare chance to test debris formation |access-date=22 May 2019 |archive-url=https://web.archive.org/web/20190516161457/http://www.esa.int/Our_Activities/Space_Safety/Rocket_break-up_provides_rare_chance_to_test_debris_formation |archive-date=16 May 2019 |url-status=live}}</ref><ref>{{cite web |url=https://twitter.com/18SPCS/status/1121184362559496192 |title=Confirmed breakup of Atlas 5 Centaur R/B (2018-079B, #43652) on April 6, 2019 |access-date=22 May 2019 |archive-url=https://web.archive.org/web/20190502164548/https://twitter.com/18spcs/status/1121184362559496192 |archive-date=2 May 2019 |url-status=live}}</ref>
* In December 2020, scientists confirmed that a previously detected near-Earth object, 2020 SO, was rocket booster space junk launched in [[1966 in spaceflight|1966]] orbiting Earth and the Sun.<ref>{{cite news |last1=Talbert |first1=Tricia |title=New Data Confirm 2020 SO to be 1960s Upper Centaur Rocket Booster |url=https://www.nasa.gov/feature/new-data-confirm-2020-so-to-be-the-upper-centaur-rocket-booster-from-the-1960-s |access-date=16 January 2021 |work=NASA |date=2 December 2020}}</ref>
* At least eight Delta rockets have contributed orbital debris in the Sun-synchronous low Earth orbit environment. The variant of the Delta upper stage that was used in the 1970s was found to be prone to in-orbit explosions. Starting in 1981, depletion burns{{snd}}to get rid of excess propellant{{snd}}became standard and no Delta Rocket Bodies launched after 1981 experienced severe fragmentations afterward, but some of those launched prior to 1981 continued to explode. In 1991, the Delta 1975-052B fragmented, 16 years after launch, demonstrating the resilience of the propellent.<ref name="Delta Debris">{{cite web |title=50-Year Old Rocket Stage Involved in Orbital Debris Event |date=2 April 2017 |url=https://spaceflight101.com/re-entry/50-year-old-rocket-stage-involved-in-orbital-debris-event/ |access-date=13 December 2022}}</ref>

=== {{anchor|Debris from and as a weapon}}Weapons ===
{{main category|Intentionally destroyed artificial satellites}}

A former source of debris was anti-satellite weapons (ASATs) testing by the U.S. and Soviet Union during the 1960s and 1970s. [[North American Aerospace Defense Command]] (NORAD) only collected data for Soviet tests, and debris from U.S. tests were identified subsequently.<ref name=s48-note>Note that the list Schefter was presented only identified USSR ASAT tests.</ref> By the time the debris problem was understood, widespread ASAT testing had ended. The U.S. [[Program 437]] was shut down in 1975.<ref>Clayton Chun, "Shooting Down a Star: America's Thor Program 437, Nuclear ASAT, and Copycat Killers", Maxwell Air Force Base, Alabama: Air University Press, 1999. {{ISBN|1-58566-071-X}}.</ref>

The U.S. restarted their ASAT programs in the 1980s with the Vought [[ASM-135 ASAT]]. A 1985 test destroyed a {{convert|1|t|lb|adj=on}} satellite orbiting at {{convert|525|km|abbr=on}}, creating thousands of debris larger than {{convert|1|cm|abbr=on}}. At this altitude, atmospheric drag decayed the orbit of most debris within a decade. A ''de facto'' moratorium followed the test.<ref name=brief>David Wright, [http://www.ucsusa.org/assets/documents/nwgs/debris-in-brief-factsheet.pdf "Debris in Brief: Space Debris from Anti-Satellite Weapons"] {{Webarchive|url=https://web.archive.org/web/20090909005733/http://www.ucsusa.org/assets/documents/nwgs/debris-in-brief-factsheet.pdf |date=9 September 2009}} ''Union of Concerned Scientists'', December 2007.</ref>

[[File: Fengyun-1C debris.jpg|thumb|left|alt=Simulation of Earth from space, with orbit planes in red|Known orbit planes of [[Fengyun]]-1C debris one month after the weather satellite's disintegration by the [[2007 Chinese anti-satellite missile test|Chinese ASAT]]]]

China's government was condemned for the military implications and the amount of debris from the 2007 anti-satellite missile test,<ref>{{Cite web |last=David |first=Leonard |date=2007-02-02 |title=China's Anti-Satellite Test: Worrisome Debris Cloud Circles Earth |url=https://www.space.com/3415-china-anti-satellite-test-worrisome-debris-cloud-circles-earth.html |access-date=2024-04-18 |website=Space.com |language=en-us |edition=updated (last)}}</ref> the largest single space debris incident in history (creating over 2,300 pieces golf-ball size or larger, over 35,000 {{convert|1|cm|1|abbr=on}} or larger, and one million pieces {{convert|1|mm|2|abbr=on}} or larger). The target satellite orbited between {{convert|850|km|abbr=on}} and {{convert|882|km|abbr=on}}, the portion of near-Earth space most densely populated with satellites.<ref>{{Cite web |title=Fengyun 1C - Satellite Information |url=https://www.heavens-above.com/satinfo.aspx?lat=0&lng=0&alt=0&loc=Unspecified&TZ=CET&SatID=25730 |access-date=2024-04-18 |website=www.heavens-above.com}}</ref> Since atmospheric drag is low at that altitude, the debris is slow to return to Earth, and in June 2007 NASA's [[Terra (satellite)|Terra environmental spacecraft]] maneuvered to avoid impact from the debris.<ref>Brian Burger, [http://www.space.com/news/070706_sn_china_terra.html "NASA's Terra Satellite Moved to Avoid Chinese ASAT Debris"] {{Webarchive|url=https://web.archive.org/web/20080513111730/http://www.space.com/news/070706_sn_china_terra.html |date=13 May 2008 }}, ''space.com''. Retrieved 6 July 2007.</ref> Brian Weeden, U.S. Air Force officer and Secure World Foundation staff member, noted that the 2007 Chinese satellite explosion created an orbital debris of more than 3,000 separate objects that then required tracking.<ref>{{Cite news|title=Space Week: Is Space Junk Cluttering Up The Final Frontier |url=https://www.npr.org/2020/09/02/908772331/space-week-is-space-junk-cluttering-up-the-final-frontier|access-date=2020-12-02|newspaper=NPR.org}}</ref>

On 20 February 2008, the U.S. launched an [[RIM-161 Standard Missile 3|SM-3 missile]] from the [[USS Lake Erie (CG-70)|USS ''Lake Erie'']] to destroy a defective U.S. spy satellite thought to be carrying {{convert|1000|lb|kg|abbr=on|order=flip}} of toxic [[hydrazine]] propellant. The event occurred at about {{convert|250|km|0|abbr=on}}, and the resulting debris has a [[Apsis|perigee]] of {{convert|250|km|0|abbr=on}} or lower.<ref>[https://www.npr.org/templates/story/story.php?storyId=19227400 "Pentagon: Missile Scored Direct Hit on Satellite."] {{Webarchive|url=https://web.archive.org/web/20180106231726/https://www.npr.org/templates/story/story.php?storyId=19227400 |date=6 January 2018 }}, npr.org, 21 February 2008.</ref> The missile was aimed to minimize the amount of debris, which (according to Pentagon Strategic Command chief Kevin Chilton) had decayed by early 2009.<ref>Jim Wolf, [http://uk.reuters.com/article/idUKN2730646120090227 "US satellite shootdown debris said gone from space"] {{Webarchive|url=https://web.archive.org/web/20090714080228/http://uk.reuters.com/article/idUKN2730646120090227 |date=14 July 2009 }}, ''Reuters'', 27 February 2009.</ref>

On 27 March 2019, Indian Prime Minister [[Narendra Modi]] announced that India shot down one of its own LEO satellites with a ground-based missile. He stated that the operation, part of ''Mission Shakti'', would defend the country's interests in space. Afterwards, US [[Air Force Space Command]] announced they were tracking 270 new pieces of debris but expected the number to grow as data collection continues.<ref>{{cite news|title=India conducts successful anti-satellite missile operation, Prime Minister says|date=28 March 2019|last1=Chavez|first1=Nicole|last2=Pokharel|first2=Sugam|publisher=[[CNN]]|url=https://edition.cnn.com/2019/03/27/india/india-modi-satellite-missile-mission/index.html|access-date=28 March 2019|archive-url=https://web.archive.org/web/20190328034647/https://edition.cnn.com/2019/03/27/india/india-modi-satellite-missile-mission/index.html|archive-date=28 March 2019|url-status=live}}</ref>

On 15 November 2021, the Russian Defense Ministry destroyed [[Kosmos 1408]]<ref>{{Cite web|last=Berger|first=Eric|date=2021-11-16|title=Russia acknowledges anti-satellite test, but says it's no big deal|url=https://arstechnica.com/science/2021/11/russia-acknowledges-anti-satellite-test-but-says-its-no-big-deal/|access-date=2021-11-16|website=Ars Technica|language=en-us}}</ref> orbiting at around 450&nbsp;km, creating "more than 1,500 pieces of trackable debris and hundreds of thousands of pieces of un-trackable debris" according to the US State Department.<ref>{{Cite web|last=Berger|first=Eric|date=2021-11-15|title=Russia may have just shot down its own satellite, creating a huge debris cloud [Updated]|url=https://arstechnica.com/science/2021/11/debris-from-a-satellite-shot-down-by-the-russians-appears-to-threaten-the-iss/|access-date=2021-11-16|website=Ars Technica|language=en-us}}</ref>

The vulnerability of satellites to debris and the possibility of attacking LEO satellites to create debris clouds has triggered speculation that it is possible for countries unable to make a precision attack.{{clarify|date=August 2017}} An attack on a satellite of {{Convert|10|tonnes|lbs|abbr=on}} or more would heavily damage the LEO environment.<ref name=brief />

== {{anchor|Operational aspects}}Hazards ==
[[File:Space debris impact on Space Shuttle window.jpg|thumb|alt=Large glass pit (damage)|A [[micrometeoroid]] left this crater on the surface of {{OV|99}}'s front window on [[STS-7]].]]

=== To spacecraft ===
Space junk can be a hazard to active satellites and spacecraft. It has been suggested that [[Geocentric orbit|Earth orbit]] could even become impassable if the risk of collision becomes too great.<ref name=sp1/>{{failed verification|date=March 2021|reason=Kessler refuted the statement that Earth orbit could become impassible. Therefore, we need a scholarly source for such a statement by other professionals. However, this popular source contains no academic reference to this statement.}}

However, since the risk to spacecraft increases with exposure to high debris densities, it is more accurate to say that LEO would be rendered ''unusable'' by orbiting craft. The threat to craft ''passing through'' LEO to reach a higher orbit would be much lower owing to the short time span of the crossing.

==== {{anchor|Threat to uncrewed spacecraft}}Uncrewed spacecraft ====
[[File:SMM panel hole.jpg|thumb|View of an orbital debris hole made in the panel of the [[Solar Maximum Mission|Solar Max]] satellite]]
Although spacecraft are typically protected by [[Whipple shield]]s, solar panels, which are exposed to the Sun, wear from low-mass impacts. Even small impacts can produce a cloud of [[Plasma (physics)|plasma]] which is an electrical risk to the panels.<ref>{{cite journal | last1 = Akahoshi | first1 = Y. |display-authors=etal | year = 2008 | title = Influence of space debris impact on solar array under power generation |journal=International Journal of Impact Engineering | volume = 35 | issue = 12| pages = 1678–1682 |doi=10.1016/j.ijimpeng.2008.07.048| bibcode = 2008IJIE...35.1678A }}</ref>

Satellites are believed to have been destroyed by micrometeorites and (small) orbital debris (MMOD). The earliest suspected loss was of [[Kosmos 1275]], which disappeared on 24 July 1981 (a month after launch). Kosmos contained no volatile fuel, therefore, there appeared to be nothing internal to the satellite which could have caused the destructive explosion which took place. However, the case has not been proven and another hypothesis forwarded is that the battery exploded. Tracking showed it broke up, into 300 objects.<ref>{{Cite web|title=The Space Review: Regulating the void: In-orbit collisions and space debris|url=https://www.thespacereview.com/article/2520/1|access-date=2020-11-23|website=www.thespacereview.com}}</ref><!-- what about external possibilities? Other governments have done experiments with destroying satellites in orbit. It needs a source, in any case, to show it is connected to space debris. -->

Many impacts have been confirmed since. For example, on 24 July 1996, the French [[Miniaturized satellite|microsatellite]] [[Cerise (satellite)|Cerise]] was hit by fragments of an [[Ariane 1]] H-10 upper-stage booster which exploded in November 1986.<ref name=klinkrad2006/>{{rp|2}} On 29 March 2006, the Russian [[Ekspress-AM11]] communications satellite was struck by an unknown object and rendered inoperable.<ref name=srdc20060419 /> On 13 October 2009, [[Terra (satellite)|Terra]] suffered a single battery cell failure anomaly and a battery heater control anomaly which were subsequently considered likely the result of an MMOD strike.<ref name="Mission Report">{{cite journal|last1=Kelley|first1=Angelita|editor1-first=James J|editor1-last=Butler|editor2-first=Xiaoxiong (Jack)|editor2-last=Xiong|editor3-first=Xingfa|editor3-last=Gu|title=Terra mission operations: Launch to the present (and beyond)|journal=Earth Observing Systems XIX|date=17 August 2014|volume=9218|pages=92180M|doi=10.1117/12.2061253|bibcode=2014SPIE.9218E..0MK|hdl=2060/20160008917|s2cid=32269938|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160008917.pdf|access-date=5 April 2018|archive-url=https://web.archive.org/web/20171202084100/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160008917.pdf|archive-date=2 December 2017|url-status=live}}</ref> On 12 March 2010, [[Aura (satellite)|Aura]] lost power from one-half of one of its 11 solar panels and this was also attributed to an MMOD strike.<ref name="2017Status">{{cite report|last1=Fisher|first1=Dominic|title=Mission Status at Aura Science Team MOWG Meeting|date=13 June 2017|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170005606.pdf|access-date=13 December 2017}}</ref> On 22 May 2013, [[GOES 13]] was hit by an MMOD which caused it to lose track of the stars that it used to maintain an operational attitude. It took nearly a month for the spacecraft to return to operation.<ref>{{cite web |url=http://www.ssd.noaa.gov/PS/SATS/MESS/MSG1422048.01.txt |title=Product Outage/Anomaly: GOES-13 (GOES-East) Data Outage|website=www.ssd.noaa.gov |access-date=12 January 2022 |archive-url=https://web.archive.org/web/20130607192921/http://www.ssd.noaa.gov/PS/SATS/MESS/MSG1422048.01.txt |archive-date=7 June 2013 |url-status=dead}}</ref>

The [[2009 satellite collision|first major satellite collision]] occurred on 10 February 2009. The {{convert|950|kg|abbr=on}} derelict satellite [[Kosmos 2251]] and the operational {{convert|560|kg|abbr=on}} [[Iridium 33]] collided, {{convert|500|mi|abbr=on}}<ref name="n2yo">Becky Iannotta and
Tariq Malik, [http://www.space.com/news/090211-satellite-collision.html "U.S. Satellite Destroyed in Space Collision"] {{Webarchive|url=https://web.archive.org/web/20120517111956/http://www.space.com/5542-satellite-destroyed-space-collision.html |date=17 May 2012 }}, space.com, 11 February 2009</ref> over northern Siberia. The relative speed of impact was about {{convert|11.7|km/s|abbr=on}}, or about {{convert|42120|km/h|abbr=on}}.<ref>Paul Marks, [https://www.newscientist.com/article/dn16604-satellite-collision-more-powerful-than-chinas-asat-test.html "Satellite collision 'more powerful than China's ASAT test"] {{Webarchive|url=https://web.archive.org/web/20090215030344/http://www.newscientist.com/article/dn16604-satellite-collision-more-powerful-than-chinas-asat-test.html |date=15 February 2009 }}, ''New Scientist'', 13 February 2009.</ref> Both satellites were destroyed, creating thousands of pieces of new smaller debris, with legal and political liability issues unresolved even years later.<ref name=listner2012>{{cite web|url=http://www.spacesafetymagazine.com/space-debris/kessler-syndrome/iridium-33-cosmos-2251-years-later-learned-then/ |title=Iridium 33 and Cosmos 2251, Three Years Later |archive-url=https://web.archive.org/web/20190517204116/http://www.spacesafetymagazine.com/space-debris/kessler-syndrome/iridium-33-cosmos-2251-years-later-learned-then/ |archive-date=17 May 2019|first=Michael |last=Listner|publisher=Space Safety Magazine|date=10 February 2012|access-date=14 December 2019}}</ref><ref>[https://web.archive.org/web/20090214194123/http://news.yahoo.com/s/ap/20090211/ap_on_sc/satellite_collision "2 big satellites collide 500 miles over Siberia."] ''yahoo.com'', 11 February 2009. Retrieved 11 February 2009.</ref><ref name="I33-K2251">Becky Iannotta, [http://www.space.com/news/090211-satellite-collision.html "U.S. Satellite Destroyed in Space Collision"] {{Webarchive|url=https://web.archive.org/web/20120517111956/http://www.space.com/5542-satellite-destroyed-space-collision.html |date=17 May 2012 }}, space.com, 11 February 2009. Retrieved 11 February 2009.</ref> On 22 January 2013, [[BLITS (satellite)|BLITS]] (a Russian laser-ranging satellite) was struck by debris suspected to be from the [[2007 Chinese anti-satellite missile test]], changing both its orbit and rotation rate.<ref name="sdc20130310">{{cite web |author=David |first=Leonard |date=8 March 2013 |title=Russian Satellite Hit by Debris from Chinese Anti-Satellite Test |url=http://www.space.com/20138-russian-satellite-chinese-space-junk.html |url-status=live |archive-url=https://web.archive.org/web/20130311042248/http://www.space.com/20138-russian-satellite-chinese-space-junk.html |archive-date=11 March 2013 |access-date=10 March 2013 |publisher=space.com}}</ref>

Satellites sometimes{{clarify|how often does this occur? on what basis or trade-off to sat operators decide to either make a maneuver, thus using scarce propellant reserves or accept the non-zero risk of not maneuvering?|date=December 2019}} perform [[Collision avoidance (spacecraft)|Collision Avoidance Maneuvers]] and satellite operators may monitor space debris as part of maneuver planning. For example, in January 2017, the European Space Agency altered the orbit of one of its three<ref name=sn20131122>{{cite news|url=http://spacenews.com/38301swarm-satellite-trio-launched-to-study-earths-magnetic-field/|title=Swarm Satellite Trio Launched To Study Earth's Magnetic Field - SpaceNews.com|last=de Selding|first=Peter B.|date=22 November 2013|publisher=[[Space News]]|language=en-US|access-date=21 January 2023}}</ref> [[Swarm (spacecraft)|Swarm]] mission spacecraft, based on data from the US [[Joint Space Operations Center]], to lower the risk of collision from Cosmos-375, a derelict Russian satellite.<ref>{{cite news|url=https://www.cnet.com/news/european-space-agency-orbiter-russian-satellite-space-junk-this-week/|title=Space junk could take out a European satellite this week|newspaper=CNET|language=en|access-date=2017-01-25|archive-url=https://web.archive.org/web/20170125004147/https://www.cnet.com/news/european-space-agency-orbiter-russian-satellite-space-junk-this-week/|archive-date=25 January 2017|url-status=live}}</ref>

==== {{anchor|Threat to crewed spacecraft}}Crewed spacecraft ====

Crewed flights are particularly vulnerable to space debris conjunctions in the orbital path of the spacecraft. Occasional avoidance maneuvers or longer-term space debris wear have affected the space shuttle, the MIR space station, and the International Space Station.

===== Space Shuttle missions =====
[[File:STS-118 debris entry.jpg|thumb|alt=Bullet-like hole in metallic material|{{OV|105}} had a major impact on its radiator during [[STS-118]]. The entry hole is about {{cvt|5.5|mm}}, and the exit hole is twice as large.]]
From the early shuttle missions, NASA used [[NORAD]] space monitoring capabilities to assess the shuttle's orbital path for debris. In the 1980s, this consumed a large proportion of NORAD capacity.{{sfn|Schefter|1982|p=50}} The first collision-avoidance maneuver occurred during [[STS-48]], in September,1991,<ref name=encounters>Rob Matson, [http://www.satobs.org/satclose.html "Satellite Encounters"] {{Webarchive|url=https://web.archive.org/web/20101006204118/http://satobs.org/satclose.html |date=6 October 2010}} ''Visual Satellite Observer's Home Page''.</ref> a seven-second [[reaction control system|thruster burn]] to avoid debris from the derelict satellite [[Kosmos 955]].<ref>{{Cite web |last=NASA |title=STS-48 Space Shuttle Mission Report {{!}} PDF {{!}} Space Shuttle Solid Rocket Booster {{!}} Space Shuttle Main Engine |url=https://www.scribd.com/document/52642978/STS-48-Space-Shuttle-Mission-Report |access-date=2024-04-19 |website=Scribd |language=en}}</ref> Similar maneuvers were executed on missions 53, 72 and 82.<ref name=encounters />

One of the earliest events to publicize the debris problem occurred on {{OV|99}}'s second flight, STS-7. A fleck of paint struck its front window, creating a pit over {{Convert|1|mm|2|abbr=on}} wide. On [[STS-59]] in 1994, [[Space Shuttle Endeavour|''Endeavour'']]'s front window was pitted about half its depth. Minor debris impacts increased from 1998.<ref>{{cite journal | last1 = Christiansen | first1 = E. L. | last2 = Hyden | first2 = J. L. | last3 = Bernhard | first3 = R. P. | year = 2004 | title = Space Shuttle debris and meteoroid impacts | url = https://zenodo.org/record/1258748| journal = Advances in Space Research | volume = 34 | issue = 5| pages = 1097–1103 | doi = 10.1016/j.asr.2003.12.008 | bibcode=2004AdSpR..34.1097C}}</ref>

Window chipping and minor damage to [[Space Shuttle thermal protection system|thermal protection system tiles]] (TPS) were already common by the 1990s. The Shuttle was later flown tail-first to take a greater proportion of the debris load on the engines and rear cargo bay, which are not used in orbit or during descent, and thus are less critical for post-launch operation. When flying attached to the [[International Space Station|ISS]], a shuttle was flipped around so the better-armoured station shielded the orbiter.<ref name=threat />

A NASA 2005 study concluded that debris accounted for approximately half of the overall risk to the Shuttle.<ref name=threat>Kelly, John. [http://www.space.com/missionlaunches/050305_shuttle_debris.html "Debris is Shuttle's Biggest Threat"] {{Webarchive|url=https://web.archive.org/web/20090523165601/http://www.space.com/missionlaunches/050305_shuttle_debris.html |date=23 May 2009 }}, space.com, 5 March 2005.</ref><ref>"Debris Danger". ''Aviation Week & Space Technology'', Volume 169 Number 10 (15 September 2008), p. 18.</ref> Executive-level decision to proceed was required if the catastrophic impact was more likely than 1 in 200. On a normal (low-orbit) mission to the ISS, the risk was approximately 1 in 300, but the [[Hubble Space Telescope|Hubble telescope]] [[STS-125|repair mission]] was flown at the higher orbital altitude of {{convert|350|mi|km|disp=flip|abbr=on}} where the risk was initially calculated at a 1-in-185 (due in part to the 2009 satellite collision). A re-analysis with better debris numbers reduced the estimated risk to 1 in 221, and the mission went ahead.<ref>William Harwood, [http://www.spaceflightnow.com/shuttle/sts125/090416debris/ "Improved odds ease NASA's concerns about space debris"] {{Webarchive|url=https://web.archive.org/web/20090619213916/http://www.spaceflightnow.com/shuttle/sts125/090416debris/ |date=19 June 2009 }}, ''CBS News'', 16 April 2009.</ref>

Debris incidents continued on later Shuttle missions. During [[STS-115]] in 2006, a fragment of [[circuit board]] bored a small hole through the radiator panels in ''Atlantis''{{'}}s cargo bay.<ref>D. Lear et al, [http://pdf.aiaa.org/preview/CDReadyMSDM09_2047/PV2009_2361.pdf "Investigation of Shuttle Radiator Micro-Meteoroid & Orbital Debris Damage"] {{webarchive|url=https://web.archive.org/web/20120309094639/http://pdf.aiaa.org/preview/CDReadyMSDM09_2047/PV2009_2361.pdf |date=9 March 2012 }}, ''Proceedings of the 50th Structures, Structural Dynamics, and Materials Conference'', 4–7 May 2009, AIAA 2009–2361.</ref> On STS-118 in 2007, debris blew a bullet-like hole through ''Endeavour''{{'}}s radiator panel.<ref>D. Lear, et al, [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080010742_2008009999.pdf "STS-118 Radiator Impact Damage"] {{Webarchive|url=https://web.archive.org/web/20110813171837/http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080010742_2008009999.pdf|date=13 August 2011}}, NASA.</ref>

===== ''Mir'' =====
[[File:Mir on 12 June 1998edit1.jpg|thumb|upright=1.4|alt=Space station with Earth as the background|Debris impacts on ''Mir''{{'s}} solar panels degraded their performance. The damage is most noticeable on the panel on the right, which is facing the camera with a high degree of contrast. Extensive damage to the smaller panel below is due to impact with a Progress spacecraft.]]Impact wear was notable on the Soviet space station ''Mir'', since it remained in space for long periods with its original solar module panels.<ref>{{cite journal | last1 = Smirnov | first1 = V.M. |display-authors=etal | year = 2000 | title = Study of Micrometeoroid and Orbital Debris Effects on the Solar Panelson 'MIR' | journal = Space Debris | volume = 2 | issue = 1| pages = 1–7 | doi = 10.1023/A:1015607813420 | s2cid = 118628073 }}</ref><ref>[http://orbitaldebris.jsc.nasa.gov/faqs.html#9 "Orbital Debris FAQ: How did the Mir space station fare during its 15-year stay in Earth orbit?"] {{Webarchive|url=https://web.archive.org/web/20090825064237/http://orbitaldebris.jsc.nasa.gov/faqs.html#9 |date=25 August 2009 }}, ''NASA'', July 2009.</ref>

===== International Space Station =====
The ISS also uses [[Whipple shield]]ing to protect its interior from minor debris.<ref>K. Thoma et al, [http://www.cosis.net/abstracts/SPACE2005/00155/SPACE2005-A-00155.pdf "New Protection Concepts for Meteoroid / Debris Shields"] {{Webarchive|url=https://web.archive.org/web/20080409115436/http://www.cosis.net/abstracts/SPACE2005/00155/SPACE2005-A-00155.pdf|date=9 April 2008}}, ''Proceedings of the 4th European Conference on Space Debris'' (ESA SP-587), 18–20 April 2005, p. 445.</ref> However, exterior portions (notably its [[solar panel]]s) cannot be protected easily. In 1999, the ISS panels were predicted to degrade approximately 0.23% in four years due to the "sandblasting" effect of impacts with small orbital debris.<ref>Henry Nahra, [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890016664_1989016664.pdf "Effect of Micrometeoroid and Space Debris Impacts on the Space Station Freedom Solar Array Surfaces"] {{Webarchive|url=https://web.archive.org/web/20110606043107/http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890016664_1989016664.pdf |date=6 June 2011 }}. Presented at the 1989 Spring Meeting of the Materials Research Society, 24–29 April 1989, NASA TR-102287.</ref> An avoidance maneuver is typically performed for the ISS if "there is a greater than one-in-10,000 chance of a debris strike".<ref name=sn20140116 /> {{as of|2014|01}}, there have been sixteen maneuvers in the fifteen years the ISS had been in orbit.<ref name=sn20140116 /> By 2019, over 1,400 meteoroid and orbital debris (MMOD) impacts had been recorded on the ISS.<ref>{{cite conference |last1=Hyde |first1=James L. |last2=Christiansen |first2=Eric L. |last3=Lear |first3=Dana M. |url=https://www.hou.usra.edu/meetings/orbitaldebris2019/orbital2019paper/pdf/6001.pdf |title=Observations of MMOD Impact Damage to the ISS |conference=First International Orbital Debris Conference |publisher=[[Universities Space Research Association|USRA]] |date=9–12 December 2019 |access-date=8 October 2021}}</ref>

As another method to reduce the risk to humans on board, ISS operational management asked the crew to shelter in the [[Soyuz spacecraft|Soyuz]] on three occasions due to late debris-proximity warnings. In addition to the sixteen thruster firings and three Soyuz-capsule shelter orders, one attempted maneuver was not completed due to not having the several days' warning necessary to upload the maneuver timeline to the station's computer.<ref name=sn20140116 /><ref>[http://news.bbc.co.uk/2/hi/science/nature/7940431.stm "Junk alert for space station crew"] {{Webarchive|url=https://web.archive.org/web/20090318130416/http://news.bbc.co.uk/2/hi/science/nature/7940431.stm |date=18 March 2009 }}, BBC News, 12 March 2009.</ref><ref>[https://www.bbc.co.uk/news/science-environment-13949956 "International Space Station in debris scare"] {{Webarchive|url=https://web.archive.org/web/20181031193725/https://www.bbc.co.uk/news/science-environment-13949956 |date=31 October 2018 }}, BBC News, 28 June 2011.</ref> A March 2009 event involved debris believed to be a {{convert|10|cm|abbr=on}} piece of the Kosmos 1275 satellite.<ref>Haines, Lester. [https://www.theregister.co.uk/2009/03/17/iss_update/ "ISS spared space junk avoidance manoeuvre"] {{Webarchive|url=https://web.archive.org/web/20170810142014/https://www.theregister.co.uk/2009/03/17/iss_update/ |date=10 August 2017 }}, ''The Register'', 17 March 2009.</ref> In 2013, the ISS operations management did not make a [[orbital maneuver|maneuver]] to avoid any debris, after making a record four debris maneuvers the previous year.<ref name=sn20140116>{{cite news |last=de Selding|first=Peter B. |title=Space Station Required No Evasive Maneuvers in 2013 Despite Growing Debris Threat |url=https://spacenews.com/39121space-station-required-no-evasive-maneuvers-in-2013-despite-growing-debris/ |access-date=2014-01-17 |newspaper=Space News |date=2014-01-16}}</ref>

==== {{anchor|Kessler Syndrome}}Kessler syndrome ====
{{Main|Kessler syndrome}}
[[File:The growth of all tracked objects in space over time (space debris and satellites).png|thumb|upright=1.4|Growth of tracked objects in orbit and related events;<ref>{{cite journal |last1=Lawrence |first1=A. |last2=Rawls |first2=M. L. |last3=Jah |first3=M. |last4=Boley |first4=A. |last5=Di Vruno |first5=F. |last6=Garrington |first6=S. |last7=Kramer |first7=M. |last8=Lawler |first8=S. |last9=Lowenthal |first9=J. |last10=McDowell |first10=J. |last11=McCaughrean |first11=M. |title=The Case for Space Environmentalism |journal=Nature Astronomy |pages=428–435 |doi=10.1038/s41550-022-01655-6 |date=22 April 2022|volume=6 |issue=4 |arxiv=2204.10025 |bibcode=2022NatAs...6..428L |s2cid=248300127 }}</ref> efforts to manage [[Global commons#Outer space|outer space global commons]] have so far not reduced the debris or the growth of objects in orbit]]
The Kessler syndrome,<ref>{{cite web|url=http://articles.cnn.com/2002-05-03/tech/orbit.debris_1_low-earth-orbits-space-junk-international-space-station?_s=PM:TECH|title=Scientist: Space weapons pose debris threat – CNN|date=2002-05-03|website=Articles.CNN.com|archive-url=https://web.archive.org/web/20120930100948/http://articles.cnn.com/2002-05-03/tech/orbit.debris_1_low-earth-orbits-space-junk-international-space-station?_s=PM:TECH|archive-date=2012-09-30|url-status=dead|access-date=2011-03-17}}</ref><ref>{{cite web|url=https://www.theatlantic.com/past/docs/issues/98jul/junk.htm|title=The Danger of Space Junk – 98.07|website=TheAtlantic.com|first=Steve|last=Olsen|date=July 1998|access-date=2011-03-17}}</ref> proposed by NASA scientist [[Donald J. Kessler]] in 1978, is a theoretical scenario in which the density of objects in [[low Earth orbit]] (LEO) is high enough that collisions between objects could cause a cascade effect where each collision generates space debris that increases the likelihood of further collisions.{{sfn|Kessler|Cour-Palais|1978}} He further theorized that one implication, if this were to occur, is that the distribution of debris in orbit could render space activities and the use of [[satellite]]s in specific orbital ranges economically impractical for many generations.{{sfn|Kessler|Cour-Palais|1978}}

The growth in the number of objects as a result of the late-1990s studies sparked debate in the space community on the nature of the problem and the earlier dire warnings. According to Kessler's 1991 derivation and 2001 updates,{{sfn|Kessler|Anz-Meador|2001}} the LEO environment in the {{convert|1000|km|abbr=on}} altitude range should be cascading. However, only one major satellite collision incident occurred: the 2009 satellite collision between Iridium 33 and Cosmos 2251. The lack of obvious short-term cascading has led to speculation that the original estimates overstated the problem.{{sfn|Gleghorn|1995}} According to Kessler in 2010 however, a cascade may not be obvious until it is well advanced, which might take years.<ref name=graph>Jan Stupl et al, [http://swfound.org/media/28344/Stupl-DebrisAvoidanceUsingLasers.pdf "Debris-debris collision avoidance using medium power ground-based lasers"], 2010 Beijing Orbital Debris Mitigation Workshop, 18–19 October 2010, see graph p. 4 {{webarchive |url=https://web.archive.org/web/20120309055302/http://swfound.org/media/28344/Stupl-DebrisAvoidanceUsingLasers.pdf |date=9 March 2012}}</ref>

=== {{anchor|Hazard on Earth}}On Earth ===
{{Main|List of space debris fall incidents}} <!-- Please add new incidents to that list, not to this article! -->
[[File: PAM-D module crash in Saudi Arabian desert.png|thumb|alt=Cylindrical rocket fragment on sand, with men looking at it|Saudi officials inspect a crashed [[Payload Assist Module|PAM-D]] module in January 2001.]]
Although most debris burns up in the atmosphere, larger debris objects can reach the ground intact. According to NASA, an average of one cataloged piece of debris has fallen back to Earth each day for the past 50 years. Despite their size, there has been no significant property damage from the debris.<ref>Brown, M. (2012). Orbital Debris Frequently Asked Questions. Retrieved from https://orbitaldebris.jsc.nasa.gov/faq.html {{Webarchive|url=https://web.archive.org/web/20190328153512/https://orbitaldebris.jsc.nasa.gov/faq.html |date=28 March 2019 }}.</ref> Burning up in the atmosphere contributes to air pollution.<ref>{{cite news |last1=Brown |first1=Mike |title=SpaceX Starlink: how it could kickstart an 'uncontrolled experiment' |url=https://www.inverse.com/innovation/spacex-could-cause-geoengineering |access-date=28 May 2021 |work=[[Inverse (website)|Inverse]] |date=27 May 2021}}</ref> Numerous small cylindrical tanks from space objects have been found, designed to hold fuel or gasses.<ref name=pauldmaley-20220702>{{cite web |url=https://pauldmaley.com/sd1/ |title=History of Space and Launch Debris Recoveries |website=Paul D. Maley |date=2 July 2022 |access-date=31 July 2022}}</ref>

== Tracking and measurement ==
{{see also|Geodetic satellite tracking}}

=== Tracking from the ground ===
Radar and optical detectors such as [[lidar]] are the main tools for tracking space debris. Although objects under {{convert|10|cm|0|abbr=on}} have reduced orbital stability, debris as small as 1&nbsp;cm can be tracked,<ref>D. Mehrholz et al;[http://www.esa.int/esapub/bulletin/bullet109/chapter16_bul109.pdf "Detecting, Tracking and Imaging Space Debris"] {{Webarchive|url=https://web.archive.org/web/20090710221117/http://www.esa.int/esapub/bulletin/bullet109/chapter16_bul109.pdf |date=10 July 2009 }}, ESA bulletin 109, February 2002.</ref><ref>Ben Greene, [http://cddis.nasa.gov/lw13/docs/papers/adv_greene_1m.pdf "Laser Tracking of Space Debris"] {{Webarchive|url=https://web.archive.org/web/20090318001230/http://cddis.nasa.gov/lw13/docs/papers/adv_greene_1m.pdf|date=18 March 2009}}, Electro Optic Systems Pty.</ref> however determining orbits to allow re-acquisition is difficult. Most debris remain unobserved. The [[NASA Orbital Debris Observatory]] tracked space debris with a {{convert|3|m|0|abbr=on}} [[Liquid mirror telescopes|liquid mirror]] [[transit telescope]].<ref>[http://orbitaldebris.jsc.nasa.gov/measure/optical.html "Orbital debris: Optical Measurements"] {{Webarchive|url=https://web.archive.org/web/20120215233624/http://orbitaldebris.jsc.nasa.gov/measure/optical.html|date=15 February 2012}}, NASA Orbital Debris Program Office.</ref> FM Radio waves can detect debris, after reflecting off them onto a receiver.<ref>{{cite web|last=Pantaleo|first=Rick|title=Australian Scientists Track Space Junk by Listening to FM Radio|url=https://www.voanews.com/a/australian-scientists-track-space-junk-by-listening-to-fm-radio/1801950.html|work=web|date=2 December 2013 |access-date=3 December 2013|archive-url=https://web.archive.org/web/20131204143904/http://www.voanews.com/content/australian-scientists-track-space-junk-by-listening-to-fm-radio/1801950.html|archive-date=4 December 2013|url-status=live}}</ref> Optical tracking may be a useful early-warning system on spacecraft.<ref>{{cite journal|doi=10.1016/j.actaastro.2014.07.031|title=Optical orbital debris spotter|journal=Acta Astronautica|volume=104|issue=1|pages=99–105|year=2014|last1=Englert|first1=Christoph R.|last2=Bays|first2=J. Timothy|last3=Marr|first3=Kenneth D.|last4=Brown|first4=Charles M.|last5=Nicholas|first5=Andrew C.|last6=Finne|first6=Theodore T.|bibcode=2014AcAau.104...99E|doi-access=free}}</ref>

The [[United States Strategic Command|U.S. Strategic Command]] keeps a catalog of known orbital objects, using ground-based [[radar]] and telescopes, and a space-based telescope (originally to distinguish from hostile missiles). The 2009 edition listed about 19,000 objects.<ref>Grant Stokes et al, [https://web.archive.org/web/20080327212602/http://www.ll.mit.edu/ST/sbv/sbv_table_of_contents.html "The Space-Based Visible Program"], ''MIT Lincoln Laboratory''. Retrieved 8 March 2006.</ref> Other data come from the [[ESA Space Debris Telescope]], [[TIRA (System)|TIRA]],<ref name="klinkrad_~2003">{{cite web |author=Klinkrad |first=H. |date=<!-- uncertain; no date in pdf; appears to be ~2003 based on no reference in the paper to any year after 2002 --> |title=Monitoring Space – Efforts Made by European Countries |url=https://fas.org/spp/military/program/track/klinkrad.pdf |archive-url=https://web.archive.org/web/20160304063056/http://fas.org/spp/military/program/track/klinkrad.pdf |archive-date=4 March 2016 |access-date=8 March 2006 |website=fas.org}}, ''fas.org''. |date-accessed=8 March 2006.</ref> the [[Goldstone Deep Space Communications Complex|Goldstone]], [[Haystack Observatory|Haystack]],<ref>[http://www.haystack.mit.edu/ "MIT Haystack Observatory"] {{Webarchive|url=https://web.archive.org/web/20041129212159/http://www.haystack.mit.edu/ |date=29 November 2004 }} haystack.mit.edu. Retrieved 8 March 2006.</ref> and [[EISCAT]] radars and the [[Cobra Dane]] [[phased array]] radar,<ref>[https://fas.org/spp/military/program/track/cobra_dane.htm "AN/FPS-108 COBRA DANE."] {{Webarchive|url=https://web.archive.org/web/20160205105011/http://fas.org/spp/military/program/track/cobra_dane.htm |date=5 February 2016 }} ''fas.org''. Retrieved 8 March 2006.</ref> to be used in debris-environment models like the ESA Meteoroid and Space Debris Terrestrial Environment Reference (MASTER).

=== Measurement in space ===
[[File:STS-41-C-LDEF-deploy-small.jpg|thumb|alt=Large, cylindrical spacecraft against Earth background, photographed from the ''Challenger'' space shuttle|The [[Long Duration Exposure Facility]] (LDEF) is an important source of information on small-particle space debris.]]
Returned space hardware is a valuable source of information on the directional distribution and composition of the (sub-millimetre) debris flux. The [[LDEF]] satellite deployed by mission [[STS-41-C]] ''Challenger'' and retrieved by [[STS-32]] ''[[Space Shuttle Columbia|Columbia]]'' spent 68 months in orbit to gather debris data. The [[European Retrievable Carrier|EURECA]] satellite, deployed by [[STS-46]] ''[[Space Shuttle Atlantis|Atlantis]]'' in 1992 and retrieved by [[STS-57]] ''Endeavour'' in 1993, was also used for debris study.<ref>Darius Nikanpour, [https://www.mcgill.ca/files/iasl/Session_1_Darius_Nikanpour.pdf "Space Debris Mitigation Technologies"] {{webarchive|url=https://web.archive.org/web/20121019134008/http://www.mcgill.ca/files/iasl/Session_1_Darius_Nikanpour.pdf |date=19 October 2012 }}, ''Proceedings of the Space Debris Congress'', 7–9 May 2009.</ref>

The [[Photovoltaic system|solar arrays]] of Hubble were returned by missions [[STS-61]] ''Endeavour'' and [[STS-109]] ''Columbia'', and the [[impact craters]] studied by the ESA to validate its models. Materials returned from Mir were also studied, notably the [[Mir Environmental Effects Payload]] (which also tested materials intended for the ISS<ref name="MEEP PR">{{cite web|url=http://www.nasa.gov/centers/langley/news/releases/1996/Mar96/96_13.html|access-date=8 March 2011|date=March 1996|title=STS-76 Mir Environmental Effects Payload (MEEP)|publisher=NASA|archive-url=https://web.archive.org/web/20110418155037/http://www.nasa.gov/centers/langley/news/releases/1996/Mar96/96_13.html|archive-date=18 April 2011|url-status=live}}</ref>).<ref>[http://spaceflight.nasa.gov/history/shuttle-mir/spacecraft/s-mir-meep-main.htm MEEP] {{Webarchive|url=https://web.archive.org/web/20110605235939/http://spaceflight.nasa.gov/history/shuttle-mir/spacecraft/s-mir-meep-main.htm|date=5 June 2011}}, NASA, 4 April 2002. Retrieved 8 July 2011.</ref><ref>[http://www.nasa.gov/centers/langley/news/releases/1996/Mar96/96_13.html "STS-76 Mir Environmental Effects Payload (MEEP)"] {{Webarchive|url=https://web.archive.org/web/20110629040749/http://www.nasa.gov/centers/langley/news/releases/1996/Mar96/96_13.html |date=29 June 2011 }}, NASA, March 1996. Retrieved 8 March 2011.</ref>

=== Gabbard diagrams ===
A debris cloud resulting from a single event is studied with [[scatter plot]]s known as Gabbard diagrams, where the [[perigee]] and [[apogee]] of fragments are plotted with respect to their [[orbital period]]. Gabbard diagrams of the early debris cloud prior to the effects of perturbations, if the data were available, are reconstructed. They often include data on newly observed, as yet uncatalogued fragments. Gabbard diagrams can provide insights into the features of the fragmentation, the direction and point of impact.<ref name=portree>David Portree and Joseph Loftus. [http://ston.jsc.nasa.gov/collections/TRS/_techrep/TP-1999-208856.pdf "Orbital Debris: A Chronology"] {{webarchive|url=https://web.archive.org/web/20000901071135/http://ston.jsc.nasa.gov/collections/TRS/_techrep/TP-1999-208856.pdf |date=1 September 2000 }}, NASA, 1999, p. 13.</ref><ref>David Whitlock, [http://www.orbitaldebris.jsc.nasa.gov/library/SatelliteFragHistory/13thEditionofBreakupBook.pdf "History of On-Orbit Satellite Fragmentations"] {{Webarchive|url=https://web.archive.org/web/20060103175108/http://www.orbitaldebris.jsc.nasa.gov/library/SatelliteFragHistory/13thEditionofBreakupBook.pdf|date=3 January 2006}}, NASA Johnson Space Center, 2004.</ref>

== Dealing with debris ==
[[File:WT-reentry-fireball-tight.jpg|thumb|Space debris identified as WT1190F, burning up in a fireball over Sri Lanka]]
An average of about one tracked object per day has been dropping out of orbit for the past 50 years,<ref name=ss20111205b /> averaging almost three objects per day at [[solar maximum]] (due to the heating and expansion of the Earth's atmosphere), but one about every three days at [[solar minimum]], usually five and a half years later.<ref name=ss20111205b>{{cite web |last=Johnson |first=Nicholas |title=Space debris issues |date=5 December 2011 |url=http://www.thespaceshow.com/detail.asp?q=1666 |work=audio file, @0:05:50–0:07:40 |publisher=The Space Show |access-date=8 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120127055806/http://thespaceshow.com/detail.asp?q=1666 |archive-date=27 January 2012}}</ref> In addition to natural atmospheric effects, corporations, academics and government agencies have proposed plans and technology to deal with space debris, but {{as of|2014|11|lc=y}}, most of these are theoretical, and there is no business plan for debris reduction.<ref name=sn20141125/>

A number of scholars have also observed that institutional factors{{snd}}political, legal, economic, and cultural "rules of the game"{{snd}}are the greatest impediment to the cleanup of near-Earth space. There is little commercial incentive to act, since [[Negative externality|costs are not assigned to polluters]], though a number of technological solutions have been suggested.<ref name=sn20141125 /> However, effects to date are limited. In the US, governmental bodies have been accused of backsliding on previous commitments to limit debris growth, "let alone tackling the more complex issues of removing orbital debris."<ref name=sn20141124>{{cite news |last1=Foust|first1=Jeff |title=Industry Worries Government 'Backsliding' on Orbital Debris |url=http://www.spacenews.com/article/civil-space/42634industry-worries-government-%E2%80%98backsliding%E2%80%99-on-orbital-debris |archive-url=https://archive.today/20141208181506/http://www.spacenews.com/article/civil-space/42634industry-worries-government-%E2%80%98backsliding%E2%80%99-on-orbital-debris |url-status=dead |archive-date=2014-12-08 |access-date=2014-12-08 |work=Space News |date=2014-11-24 |quote=Despite growing concern about the threat posed by orbital debris, and language in U.S. national space policy directing government agencies to study debris cleanup technologies, many in the space community worry that the government is not doing enough to implement that policy.}}</ref> The different methods for removal of space debris have been evaluated by the [[Space Generation Advisory Council]], including French astrophysicist [[Fatoumata Kébé]].<ref>{{cite web|url=https://eandt.theiet.org/content/articles/2018/06/women-of-nasa-past-present-and-future/|title=Women of Nasa: past, present and future|last=Northfield|first=Rebecca|date=2018-06-20|website=eandt.theiet.org|language=en-US|access-date=2019-01-20|archive-url=https://web.archive.org/web/20190121010822/https://eandt.theiet.org/content/articles/2018/06/women-of-nasa-past-present-and-future/|archive-date=21 January 2019|url-status=live}}</ref>

In May 2024, a NASA report from the Office of Technology, Policy, and Strategy (OTPS) introduced new methods for addressing orbital debris. The report, titled ''Cost and Benefit Analysis of Mitigating, Tracking, and Remediating Orbital Debris'',<ref>{{Cite web |date=2024-05-20 |title=NASA Study Provides New Look at Orbital Debris, Potential Solutions - NASA |url=https://www.nasa.gov/organizations/otps/nasa-study-provides-new-look-at-orbital-debris-potential-solutions/ |access-date=2024-05-21 |language=en-US}}</ref> provided a comprehensive analysis comparing the cost-effectiveness of over ten different actions, including shielding spacecraft, tracking smaller debris, and removing large debris. By evaluating these measures in economic terms, the study aims to inform cost-effective strategies for debris management, highlighting that methods like rapid deorbiting of defunct spacecraft can significantly reduce risks in space.

=== National and international regulation ===
[[File:Debris-sAfrica.jpg|thumb|After reentry, Delta 2 second stage pieces were found in South Africa.]]
There is no international treaty minimizing space debris. However, the [[United Nations Committee on the Peaceful Uses of Outer Space]] (COPUOS) published voluntary guidelines in 2007,<ref>[http://orbitaldebris.jsc.nasa.gov/library/Space%20Debris%20Mitigation%20Guidelines_COPUOS.pdf "UN Space Debris Mitigation Guidelines"] {{Webarchive|url=https://web.archive.org/web/20111006081815/http://orbitaldebris.jsc.nasa.gov/library/Space%20Debris%20Mitigation%20Guidelines_COPUOS.pdf |date=6 October 2011 }}, UN Office for Outer Space Affairs, 2010.</ref> using a variety of earlier national regulatory attempts at developing standards for debris mitigation. As of 2008, the committee was discussing international "rules of the road" to prevent collisions between satellites.<ref>Theresa Hitchens, [http://www.thebulletin.org/web-edition/features/copuos-wades-the-next-great-space-debate "COPUOS Wades into the Next Great Space Debate"] {{webarchive|url=https://web.archive.org/web/20081226123125/http://thebulletin.org/web-edition/features/copuos-wades-the-next-great-space-debate |date=26 December 2008 }}, ''The Bulletin of the Atomic Scientists'', 26 June 2008.</ref> By 2013, a number of national legal regimes existed,<ref name=us20131128>
{{cite web |title=U.S. Government Orbital Debris Mitigation Standard Practices |url=http://orbitaldebris.jsc.nasa.gov/library/USG_OD_Standard_Practices.pdf |publisher=United States Federal Government |access-date=2013-11-28 |archive-url=https://web.archive.org/web/20130216201001/http://www.orbitaldebris.jsc.nasa.gov/library/USG_OD_Standard_Practices.pdf |archive-date=16 February 2013 |url-status=live }}</ref><ref name=nasaOrbDebris>[http://orbitaldebris.jsc.nasa.gov/library/references.html "Orbital Debris – Important Reference Documents."] {{Webarchive|url=https://web.archive.org/web/20090320154827/http://orbitaldebris.jsc.nasa.gov/library/references.html |date=20 March 2009 }}, NASA Orbital Debris Program Office.</ref><ref name=esa20130419/> typically instantiated in the launch licenses that are required for a launch in all spacefaring [[Nation state|nations]].<ref name=ssm20130718>{{cite news |url=http://www.spacesafetymagazine.com/space-debris/mitigation/compliance-rocket-upper-stage-gto-space-debris-mitigation-guidelines/ |title=Compliance of Rocket Upper Stages in GTO with Space Debris Mitigation Guidelines |work=Space Safety Magazine |date=2013-07-18 |access-date=2016-02-16 }}</ref>

The U.S. issued a set of standard practices for civilian (NASA) and military ([[United States Department of Defense|DoD]] and USAF) orbital-debris mitigation in 2001.<ref name="sn20191209">{{cite news |last=Foust |first=Jeff |date=9 December 2019 |title=U.S. government updates orbital debris mitigation guidelines |url=https://spacenews.com/u-s-government-updates-orbital-debris-mitigation-guidelines/ |access-date=14 December 2019 |work=[[SpaceNews]] |quote=''the first update of the guidelines since their publication in 2001, and reflect a better understanding of satellite operations and other technical issues that contribute to the growing population of orbital debris. ...[The new 2019 guidelines] did not address one of the biggest issues regarding debris mitigation: whether to reduce the 25-year timeframe for deorbiting satellites after the end of their mission. Many in the space community believe that timeframe should be less than 25 years.''}}</ref><ref name=us20040405>{{cite web |title=U.S. Government Orbital Debris Mitigation Standard Practices |url=http://orbitaldebris.jsc.nasa.gov/library/USG_OD_Standard_Practices.pdf |publisher=United States Federal Government |access-date=13 December 2019 |archive-url=https://web.archive.org/web/20040405213600/http://www.orbitaldebris.jsc.nasa.gov/library/USG_OD_Standard_Practices.pdf |archive-date=5 April 2004 |url-status=live }}</ref><ref name=nasaOrbDebris/><!-- have not been able to locate a web-accessible version earlier than 200404. N2e, 12 Dec 2019 --> The standard envisioned disposal for final mission orbits in one of three ways: 1) atmospheric reentry where even with "conservative projections for solar activity, atmospheric drag will limit the lifetime to no longer than 25 years after completion of mission;" 2) maneuver to a "storage orbit:" move the spacecraft to one of four very broad [[parking orbit]] ranges ({{cvt|2000|–|19700|km}}, {{cvt|20700|–|35300|km}}, above {{cvt|36100|km}}, or out of Earth orbit completely and into any [[heliocentric orbit]]; 3) "Direct retrieval: Retrieve the structure and remove it from orbit as soon as practicable after completion of mission."<ref name=us20131128/> The standard articulated in option 1, which is the standard applicable to most satellites and derelict upper stages, has come to be known as the "25-year rule".<ref name=7thECSD2017/> The US updated the Orbital Debris Mitigation Standard Practices (ODMSP) in December 2019, but made no change to the 25-year rule even though "[m]any in the space community believe that the timeframe should be less than 25 years."<ref name=":7">{{Cite web |last=Foust |first=Jeff |date=2019-12-10 |title=U.S. government updates orbital debris mitigation guidelines |url=https://spacenews.com/u-s-government-updates-orbital-debris-mitigation-guidelines/ |access-date=2022-08-11 |website=SpaceNews |language=en-US}}</ref> There is no consensus however on what any new timeframe might be.<ref name=":7" />

In 2002, the European Space Agency (ESA) worked with an international group to promulgate a similar set of standards, also with a "25-year rule" applying to most Earth-orbit satellites and upper stages. Space agencies in Europe began to develop technical guidelines in the mid-1990s, and [[Italian Space Agency|ASI]], [[UK Space Agency|UKSA]], [[CNES]], [[German Space Agency|DLR]] and ESA signed a "European Code of Conduct" in 2006,<ref name=esa20130419>{{cite web |url=http://www.esa.int/Our_Activities/Operations/Space_Debris/Mitigating_space_debris_generation |title=Mitigating space debris generation |date=19 April 2013 |publisher=European Space Agency |access-date=13 December 2019 |archive-url=https://web.archive.org/web/20130426093202/http://www.esa.int/Our_Activities/Operations/Space_Debris/Mitigating_space_debris_generation |archive-date=26 April 2013<!--20130426 is the oldest archive of this url available on web.archive.org --> |url-status=live}}</ref> which was a predecessor standard to the ISO international standard work that would begin the following year. In 2008, ESA further developed "its own "Requirements on Space Debris Mitigation for Agency Projects" which "came into force on 1 April 2008."<ref name=esa20130419/>

Germany and France have posted [[Bond (finance)|bonds]] to safeguard property from debris damage.{{clarify|to what extent is this required by national or European regulations in order to get a launch license?|date=December 2019}}<ref>{{cite web|last=Howell|first=Elizabeth|date=28 April 2013|title=Experts Urge Removal of Space Debris From Orbit|publisher=Universe Today|url=http://www.universetoday.com/101790/experts-urge-removal-of-space-debris-from-orbit/ |archive-url=https://web.archive.org/web/20140305014548/http://www.universetoday.com/101790/experts-urge-removal-of-space-debris-from-orbit/ |archive-date=5 March 2014}}</ref> The "direct retrieval" option (option no. 3 in the US "standard practices" above) has rarely been done by any spacefaring nation (exception, USAF [[X-37]]) or commercial actor since the earliest days of spaceflight due to the cost and complexity of achieving direct retrieval, but the ESA has scheduled a 2026 demonstration mission ([[ClearSpace-1]]) to do this with a single small {{cvt|94|kg}} satellite ([[PROBA-1]])<ref name="sn-20240424">{{cite web |last=Werner |first=Debra |url=https://spacenews.com/major-changes-approved-for-clearspace-1-mission/ |title=Major changes approved for ClearSpace-1 mission |work=[[SpaceNews]] |date=24 April 2024 |access-date=24 April 2024}}</ref> at a projected cost of €120 million not including the launch costs.<ref name="guardian20191209" />

By 2006, the Indian Space Research Organization (ISRO) had developed a number of technical means of debris mitigation (upper stage passivation, propellant reserves for movement to graveyard orbits, etc.) for ISRO launch vehicles and satellites, and was actively contributing to inter-agency debris coordination and the efforts of the UN COPUOS committee.<ref>{{cite journal |last1=Adimurthya |first1=V. |last2=Ganeshanb |first2=A. S. |date=February 2006 |title=Space debris mitigation measures in India |url=https://www.sciencedirect.com/science/article/abs/pii/S0094576505002961 |journal=Acta Astronautica |volume=58 |issue=3 |pages=168-174<!-- article is behind a paywall; could only reference the abstract in 2019 --> |bibcode=2006AcAau..58..168A |doi=10.1016/j.actaastro.2005.09.002 |archive-url=https://web.archive.org/web/20191213184006/https://www.sciencedirect.com/science/article/abs/pii/S0094576505002961 |archive-date=13 December 2019|url-access=subscription }}</ref><!-- it is unclear what regulations or standards are required of Indian launch vehicles and satellites by the government of India; other sources would be helpful here. -->
<!-- as of August 2019, ISRO is building a Space Situational Awareness and Management (SSAM) center, but that article is not about the general problem of space debris nor the national regulatory debris mitigation part of the problem, although it is apparently intended to be involved in debris mitigation research: https://timesofindia.indiatimes.com/india/isro-keen-on-protecting-space-assets-new-centre-soon/articleshow/70520904.cms -->

In 2007, the [[International Organization for Standardization|ISO]] began preparing an [[international standard]] for space-debris mitigation.<ref>E. A. Taylor and J. R. Davey, [http://pig.sagepub.com/content/221/6/987.full.pdf "Implementation of debris mitigation using International Organization for Standardization (ISO) standards"] {{Webarchive|url=https://web.archive.org/web/20120309094645/http://pig.sagepub.com/content/221/6/987.full.pdf|date=9 March 2012}}, ''Proceedings of the Institution of Mechanical Engineers: G,'' Volume 221, Number 8 (1 June 2007), pp. 987–996.</ref> By 2010, ISO had published "a comprehensive set of space system engineering standards aimed at mitigating space debris. [with primary requirements] defined in the top-level standard, '''ISO 24113'''<!-- bolded per [[WP:MOSBOLD]] as a redirect target -->." By 2017, the standards were nearly complete. However, these standards are not binding on any party by ISO or any international jurisdiction. They are simply available for use in voluntary ways. They "can be adopted voluntarily by a spacecraft manufacturer or operator, or brought into effect through a commercial contract between a customer and supplier, or used as the basis for establishing a set of national regulations on space debris mitigation."<ref name=7thECSD2017>{{cite conference |last1=Stokes |display-authors=etal |title=Status of the ISO Space Debris Mitigation Standards(2017) |url=https://conference.sdo.esoc.esa.int/proceedings/sdc7/paper/979/SDC7-paper979.pdf |conference=7th European Conference on Space Debris, Darmstadt, Germany, 18–21 April 2017 |editor-last=Flohrer |editor-first=T. |editor2-last=Schmitz |editor2-first=F. |publisher=ESA Space Debris Office |access-date=13 December 2019 |archive-url=https://web.archive.org/web/20191213184145/https://conference.sdo.esoc.esa.int/proceedings/sdc7/paper/979/SDC7-paper979.pdf |archive-date=13 December 2019 |url-status=live}}</ref>

[[File:Why space debris mitigation is needed ESA289519.gif|thumb|300x300px|A computer-generated animation by the [[European Space Agency]] representing space debris in low earth orbit at the current rate of growth compared to mitigation measures being taken]]

The voluntary ISO standard also adopted the "25-year rule" for the "LEO protected region" below {{Convert|2000|km|mi|abbr=on}} altitude that has been previously (and still is, {{As of|2019|lc=y}}) used by the US, ESA, and UN mitigation standards, and identifies it as "an upper limit for the amount of time that a space system shall remain in orbit after its mission is completed. Ideally, the time to deorbit should be as short as possible (i.e., much shorter than 25 years)".<ref name="7thECSD2017" />
<!-- Do we have any sources that indicate if Russian/Roscosmos, India/ISRO, China/CNSA, Japan/JAXA have promulgated debris mitigation standards for the launches under their jurisdiction? -->

Holger Krag of the European Space Agency states that as of 2017 there is no binding international regulatory framework with no progress occurring at the respective UN body in Vienna.<ref name="sp1">{{cite news |last1=Seidler |first1=Christoph |date=22 April 2017 |title=Problem Weltraumschrott: Die kosmische Müllkippe |url=http://www.spiegel.de/wissenschaft/weltall/weltraumschrott-esa-tagung-in-darmstadt-ohne-ergebnisse-a-1144174.html |url-status=live |archive-url=https://web.archive.org/web/20170423013706/http://www.spiegel.de/wissenschaft/weltall/weltraumschrott-esa-tagung-in-darmstadt-ohne-ergebnisse-a-1144174.html |archive-date=23 April 2017 |access-date=22 April 2017 |newspaper=Der Spiegel – Wissenschaft (Online) |publisher= |language=de}}</ref>

=== Growth mitigation ===
{{See also|Space traffic management}}
[[File:SpaceDebrisHistogram.png|thumb|upright=1.4|alt=Graph with blue line|Spatial density of LEO space debris by altitude, according to 2011 a NASA report to the [[United Nations Office for Outer Space Affairs]]<ref>{{cite web|title=USA Space Debris Environment, Operations, and Policy Updates|url=https://www.unoosa.org/pdf/pres/stsc2011/tech-31.pdf|work=NASA|publisher=UNOOSA|access-date=3 March 2021}}</ref>]]
[[File: Spacedebris small.png|thumb|upright=1.4|alt=Graph with red line|Spatial density of space debris by altitude according to ESA MASTER-2001, without debris from the Chinese ASAT and 2009 collision events]]
As of the 2010s, several technical approaches to the mitigation of the growth of space debris are typically undertaken, yet no comprehensive legal regime or cost assignment structure is in place to reduce space debris in the way that terrestrial pollution has reduced since the mid-20th century.

To avoid excessive creation of artificial space debris, many{{snd}}but not all{{snd}}satellites launched to above-low-Earth-orbit are launched initially into [[elliptical orbit]]s with [[perigee]]s inside Earth's atmosphere so the orbit will quickly decay and the satellites then will be destroyed upon [[Atmospheric reentry|reentry]] into the atmosphere. Other methods are used for spacecraft in higher orbits. These include [[Passivation (spacecraft)|passivation]] of the spacecraft at the end of its useful life; as well as the use of upper stages that can reignite to decelerate the stage to intentionally deorbit it, often on the first or second orbit following payload release; satellites that can, if they remain healthy for years, deorbit themselves from the lower orbits around Earth. Other satellites (such as many CubeSats) in low orbits below approximately {{Convert|400|km|mi|abbr=on}} orbital altitude depend on the energy-absorbing effects of the upper atmosphere to reliably deorbit a spacecraft within weeks or months.

Increasingly, [[:wikt:spent|spent]] upper stages in higher orbits{{snd}}orbits for which low-delta-v deorbit is not possible, or not planned for{{snd}}and architectures that support satellite passivation, are passivated at end of life. This removes any internal energy contained in the vehicle at the end of its mission or useful life. While this does not remove the debris of the now derelict rocket stage or satellite itself, it does substantially reduce the likelihood of the spacecraft destructing and creating many smaller pieces of space debris, a phenomenon that was common in many of the early generations of US and Soviet<ref name=rossi1997/> spacecraft.

Upper stage passivation (e.g. of [[Delta (rocket family)|Delta boosters]]{{sfn|Schefter|1982|p=50}}) achieved by releasing residual propellants reduces debris from orbital explosions; however even as late as 2011, not all upper stages implement this practice.<ref name=ss20111205>{{cite web |last=Johnson |first=Nicholas |title=Space debris issues |date=5 December 2011 |url=http://www.thespaceshow.com/detail.asp?q=1666 |work=audio file, @1:03:05–1:06:20 |publisher=The Space Show |access-date=8 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120127055806/http://thespaceshow.com/detail.asp?q=1666 |archive-date=27 January 2012}}</ref> SpaceX used the term "propulsive passivation" for the final maneuver of their six-hour demonstration mission ([[STP-2]]) of the Falcon 9 second stage for the US Air Force in 2019, but did not define what all that term encompassed.<ref name="trati201904">{{cite news |author=Ralph |first=Eric |date=19 April 2019 |title=SpaceX's Falcon Heavy flies a complex mission for the Air Force in launch video |url=https://www.teslarati.com/spacex-falcon-heavy-next-launch-video/ |url-status=live |archive-url=https://web.archive.org/web/20190825035407/https://www.teslarati.com/spacex-falcon-heavy-next-launch-video/ |archive-date=25 August 2019 |access-date=14 December 2019 |work=Teslarati}}</ref>

With a "one-up, one-down" launch-license policy for Earth orbits, launchers would rendezvous with, capture, and de-orbit a derelict satellite from approximately the same orbital plane.<ref name=aiaa20100902 /> Another possibility is the [[Mission Extension Vehicle|robotic]] [[Space Infrastructure Servicing|refueling]] of satellites. Experiments have been flown by NASA,<ref>{{Cite web |url=http://www.nasa.gov/mission_pages/station/research/experiments/RRM.html |title=Robotic refueling Mission |access-date=30 July 2012 |archive-url=https://web.archive.org/web/20110810002223/http://www.nasa.gov/mission_pages/station/research/experiments/RRM.html |archive-date=10 August 2011 |url-status=dead }}</ref> and SpaceX is developing large-scale on-orbit propellant transfer technology.<ref name=nsf20160927>{{cite news |last=Bergin |first=Chris |url=https://www.nasaspaceflight.com/2016/09/spacex-reveals-mars-game-changer-colonization-plan/ |title=SpaceX reveals ITS Mars game changer via colonization plan |work=[[NASASpaceFlight.com]] |date=2016-09-27 |access-date=2016-10-21 |archive-url=https://web.archive.org/web/20160928154300/https://www.nasaspaceflight.com/2016/09/spacex-reveals-mars-game-changer-colonization-plan/ |archive-date=28 September 2016 |url-status=live}}</ref>

Another approach to debris mitigation is to explicitly design the mission architecture to leave the rocket second-stage in an [[elliptic orbit|elliptical]] [[geocentric orbit]] with a low-perigee, thus ensuring rapid [[orbital decay]] and avoiding long-term orbital debris from spent rocket bodies. Such missions will often complete the payload placement in a final orbit by the use of low-thrust [[electric propulsion]] or with the use of a small [[Apogee kick motor|kick stage]] to circularize the orbit. The kick stage itself may be designed with the excess-propellant capability to be able to self-deorbit.<ref>{{cite web |url=https://www.nasaspaceflight.com/2018/03/rocket-lab-capitalize-test-flight-success-first-operational-mission/ |title=Rocket Lab to capitalize on test flight success with first operational mission |date=7 March 2018 |archive-url=https://web.archive.org/web/20180307223205/https://www.nasaspaceflight.com/2018/03/rocket-lab-capitalize-test-flight-success-first-operational-mission/ |archive-date=7 March 2018 |url-status=live |access-date=14 March 2020}}</ref>

=== Self-removal ===
Although the ITU requires geostationary satellites to move to a graveyard orbit at the end of their lives, the selected orbital areas do not sufficiently protect GEO lanes from debris.<ref name= Anselmo /> Rocket stages (or satellites) with enough propellant may make a direct, controlled de-orbit, or if this would require too much propellant, a satellite may be brought to an orbit where atmospheric drag would cause it to eventually de-orbit. This was done with the French [[SPOT (satellites)|Spot-1 satellite]], reducing its atmospheric re-entry time from a projected 200 years to about 15 by lowering its altitude from {{convert|830|km|0|abbr=on}} to about {{convert|550|km|0|abbr=on}}.<ref>Luc Moliner, [http://www.aiaa.org/spaceops2002archive/papers/SpaceOps02-P-T3-30.pdf "Spot-1 Earth Observation Satellite Deorbitation"] {{webarchive|url=https://web.archive.org/web/20110116030335/http://www.aiaa.org/Spaceops2002Archive/papers/SpaceOps02-P-T3-30.pdf |date=16 January 2011 }}, AIAA, 2002.</ref><ref>[http://www.agi.com/resources/downloads/data/spacecraft-digest/display.aspx?i=3352 "Spacecraft: Spot 3"] {{webarchive|url=https://web.archive.org/web/20110930142847/http://www.agi.com/resources/downloads/data/spacecraft-digest/display.aspx?i=3352|date=30 September 2011}}, agi, 2003.</ref>

The [[Iridium satellite constellation|Iridium constellation]] – 95 communication satellites launched during the five-year period between 1997 and 2002 – provides a set of data points on the limits of self-removal. The satellite operator – [[Iridium Communications]] – remained operational over the two-decade life of the satellites (albeit with a company name change through a corporate bankruptcy during the period) and, by December 2019, had "completed disposal of the last of its 65 working legacy satellites."<ref name="sn20191220">{{cite news |author=Henry |first=Caleb |date=30 December 2019 |title=Iridium would pay to deorbit its 30 defunct satellites – for the right price |url=https://spacenews.com/iridium-would-pay-to-deorbit-its-30-defunct-satellites-for-the-right-price/ |access-date=2 January 2020 |work=[[SpaceNews]]}}</ref> However, this process left 30 satellites with a combined mass of ({{cvt|{{#expr:30*680}}|kg}}, or nearly a third of the mass of this constellation) in LEO orbits at approximately {{cvt|700|km}} altitude, where self-decay is quite slow. Of these satellites, 29 simply failed during their time in orbit and were thus unable to self-deorbit, while one – Iridium 33 – was involved in the 2009 satellite collision with the [[Derelict satellite|derelict]] Russian military satellite [[Kosmos-2251]].<ref name=sn20191220/> No contingency plan was laid for the removal of satellites that were unable to remove themselves. In 2019, the CEO of Iridium, Matt Desch, said that Iridium would be willing to pay an active-debris-removal company to deorbit its remaining first-generation satellites if it were possible for an unrealistically low cost, say "{{USD|10,000}} per deorbit, but [he] acknowledged that price would likely be far below what a debris-removal company could realistically offer. 'You know at what point [it's] a no-brainer, but [I] expect the cost is really in the millions or tens of millions, at which price I know it doesn't make sense.{{'}}"<ref name=sn20191220/>

Passive methods of increasing the orbital decay rate of spacecraft debris have been proposed. Instead of rockets, an [[electrodynamic tether]] could be attached to a spacecraft at launch; at the end of its lifetime, the tether would be rolled out to slow the spacecraft.<ref>Bill Christensen, [http://www.space.com/businesstechnology/technology/technovel_tether_041117.html "The Terminator Tether Aims to Clean Up Low Earth Orbit"] {{Webarchive|url=https://web.archive.org/web/20091126050042/http://www.space.com/businesstechnology/technology/technovel_tether_041117.html |date=26 November 2009}}, space.com. Retrieved 8 March 2006.</ref> Other proposals include a booster stage with a sail-like attachment<ref>Jonathan Amos, [http://news.bbc.co.uk/2/hi/science/nature/8029899.stm "How satellites could 'sail' home"] {{Webarchive|url=https://web.archive.org/web/20090701001659/http://news.bbc.co.uk/2/hi/science/nature/8029899.stm |date=1 July 2009}}, BBC News, 3 May 2009.</ref> and a large, thin, inflatable balloon envelope.<ref name=sd20100803>{{cite news |title=Safe And Efficient De-Orbit of Space Junk Without Making The Problem Worse |url=http://www.spacedaily.com/reports/Safe_And_Efficient_De_Orbit_Of_Space_Junk_Without_Making_The_Problem_Worse_999.html |access-date=2013-09-16 |newspaper=Space Daily |date=2010-08-03 |archive-url=https://web.archive.org/web/20131014215454/http://www.spacedaily.com/reports/Safe_And_Efficient_De_Orbit_Of_Space_Junk_Without_Making_The_Problem_Worse_999.html |archive-date=14 October 2013 |url-status=live }}</ref>

In late December 2022, ESA successfully carried out a demonstration of a breaking sail-based satellite deorbiter, {{tooltip|ADEO|Drag Augmentation Deorbiting System}}, which could be used by mitigation measures and is part of ESA's Zero Debris Initiative. Around one year earlier, China also tested a drag sail.<ref>{{cite news |last1=Young |first1=Chris |title=ESA successfully deploys braking sail for deorbiting small satellites |url=https://interestingengineering.com/innovation/esa-braking-sail-deorbiting-small-satellites |access-date=15 February 2023 |work=interestingengineering.com |date=9 February 2023 |archive-date=9 February 2023 |archive-url=https://web.archive.org/web/20230209164837/https://interestingengineering.com/innovation/esa-braking-sail-deorbiting-small-satellites |url-status=live }}</ref><ref>{{cite web |title=Show Me Your Wings: Successful In-flight Demonstration of the ADEO Braking Sail |url=https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Shaping_the_Future/Show_Me_Your_Wings_Successful_In-flight_Demonstration_of_the_ADEO_Braking_Sail |website=www.esa.int |access-date=15 February 2023 |language=en |archive-date=13 February 2023 |archive-url=https://web.archive.org/web/20230213235840/https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Shaping_the_Future/Show_Me_Your_Wings_Successful_In-flight_Demonstration_of_the_ADEO_Braking_Sail |url-status=live }}</ref>

=== External removal ===
A variety of approaches have been proposed, studied, or had ground subsystems built to use other spacecraft to remove existing space debris.

A consensus of speakers at a meeting in Brussels in October 2012, organized by the Secure World Foundation (a U.S. think tank) and the French International Relations Institute,<ref>{{cite news|url=https://spacenews.com/experts-active-removal-key-countering-space-junk-threat/#.Ub3dSuce2Zc |title=Experts: Active Removal Key To Countering Space Junk Threat|first=Peter B. |last=de Selding|publisher=[[Space News]]|date= 31 October 2012|access-date=21 January 2023}}</ref> reported that removal of the largest debris would be required to prevent the risk to spacecraft becoming unacceptable in the foreseeable future (without any addition to the inventory of dead spacecraft in LEO). To date in 2019, removal costs and legal questions about ownership and the authority to remove defunct satellites have stymied national or international action. Current space law retains ownership of all satellites with their original operators, even debris or spacecraft which are defunct or threaten active missions.<ref>{{Cite journal |last=Oreshenkov |first=A. M. |date=2024-07-25 |title=Theoretical Basis of International Legal Aspect of "Space Debris" Removal |url=https://www.mjil.ru/jour/article/view/2793 |journal=Moscow Journal of International Law |issue=2 |pages=46–64 |doi=10.24833/0869-0049-2024-2-46-64 |issn=2619-0893|doi-access=free }}</ref>

Multiple companies made plans in the late 2010s to conduct external removal on their satellites in mid-LEO orbits. For example, [[OneWeb]] planned to use onboard self-removal as "plan A" for satellite deorbiting at the end of life, but if a satellite were unable to remove itself within one year of end of life, OneWeb would implement "plan B" and dispatch a reusable (multi-transport mission) space tug to attach to the satellite at an already built-in capture target via a grappling fixture, to be towed to a lower orbit and released for re-entry.<ref name="axios20191219">{{cite web| url = https://www.axios.com/space-junk-satellite-janitors-bdf897f3-81ac-40b8-b949-a944bafbc4c9.html| title = The big business of being a space janitor - Axios| date = 19 December 2019|first=Miriam|last=Kramer}}</ref><ref name="advancedtv20191212">{{Cite web |url=https://advanced-television.com/2019/12/12/oneweb-adopts-100-grappling/ |title=OneWeb adopts 100% grappling |date=12 December 2019 |access-date=22 December 2019 |archive-url=https://web.archive.org/web/20191213024352/https://advanced-television.com/2019/12/12/oneweb-adopts-100-grappling/ |archive-date=13 December 2019 |url-status=live }}</ref>

==== Remotely controlled vehicles ====
A well-studied solution uses a remotely controlled [[Orbital transfer vehicle|vehicle]] to rendezvous with, capture, and return debris to a central station.<ref name=carlson1990>Erika Carlson et al, "Final design of a space debris removal system", NASA/CR-189976, 1990.</ref> One such system is Space Infrastructure Servicing, a [[private spaceflight|commercially developed]] refueling depot and service spacecraft for communications satellites in geosynchronous orbit originally scheduled for a 2015 launch.<ref name=cnw20110315>[http://www.canadanewswire.ca/en/releases/archive/March2011/15/c2866.html "Intelsat Picks MacDonald, Dettwiler and Associates Ltd. for Satellite Servicing"] {{webarchive|url=https://web.archive.org/web/20110512175952/http://www.canadanewswire.ca/en/releases/archive/March2011/15/c2866.html |date=12 May 2011 }}, CNW Newswire, 15 March 2011. Retrieved 15 July 2011.</ref> The SIS would be able to "push dead satellites into graveyard orbits."<ref name=sn20100303>{{cite news|first=Peter|last=de Selding|url=http://spacenews.com/satellite_telecom/100303-mda-planning-inorbit-servicing-demo.html|title=MDA Designing In-orbit Servicing Spacecraft|publisher=[[Space News]]|date=3 March 2010|access-date=15 July 2011|archive-date=5 January 2013|archive-url=https://archive.today/20130105074228/http://spacenews.com/satellite_telecom/100303-mda-planning-inorbit-servicing-demo.html|url-status=dead}}</ref> The [[Advanced Common Evolved Stage]] family of upper stages is being designed with a high leftover-propellant margin (for derelict capture and de-orbit) and [[propellant depot|in-space refueling]] capability for the high [[delta-v]] required to de-orbit heavy objects from geosynchronous orbit.<ref name="aiaa20100902">Frank Zegler and Bernard Kutter, [http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf "Evolving to a Depot-Based Space Transportation Architecture"], AIAA SPACE 2010 Conference & Exposition, 30 August–2 September 2010, AIAA 2010–8638. {{webarchive|url=https://web.archive.org/web/20130510002706/http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf|date=10 May 2013}}.</ref> A tug-like satellite to drag debris to a safe altitude for it to burn up in the atmosphere has been researched.<ref>{{cite journal | last1 = Schaub | first1 = H. | last2 = Sternovsky | first2 = Z. | year = 2013 | title = Active Space Debris Charging for Contactless Electrostatic Disposal | doi = 10.1016/j.asr.2013.10.003 | journal = Advances in Space Research | volume = 53 | issue = 1| pages = 110–118 | bibcode=2014AdSpR..53..110S}}</ref> When debris is identified the satellite creates a difference in potential between the debris and itself, then using its thrusters to move itself and the debris to a safer orbit.

A variation of this approach is for the remotely controlled vehicle to rendezvous with debris, [[Spacecraft capture|capture]] it temporarily to attach a [[smallsat|smaller de-orbit satellite]] and drag the debris with a tether to the desired location. The "mothership" would then tow the debris-smallsat combination for [[atmospheric entry]] or move it to a graveyard orbit. One such system is the proposed [[ORbital DEbris Remover|Busek ORbital DEbris Remover (ORDER)]], which would carry over 40 SUL (satellite on umbilical line) de-orbit satellites and propellant sufficient for their removal.<ref name=sn20141125 />

On 7 January 2010 Star, Incorporated reported that it received a contract from the [[Space and Naval Warfare Systems Command]] for a feasibility study of the ElectroDynamic Debris Eliminator (EDDE) [[Reactionless drive|propellantless]] spacecraft for space-debris removal.<ref>[http://www.star-tech-inc.com/id68.html "News"] {{Webarchive|url=https://web.archive.org/web/20100327050344/http://www.star-tech-inc.com/id68.html|date=27 March 2010}}, Star Incorporated. Retrieved 18 July 2011.</ref> In February 2012 the Swiss Space Center at [[École Polytechnique Fédérale de Lausanne]] announced the Clean Space One project, a [[Miniaturized satellite#Nanosatellite|nanosatellite]] demonstration project for matching orbit with a defunct Swiss nanosatellite, capturing it and de-orbiting together.<ref>{{cite report |url=http://actu.epfl.ch/news/cleaning-up-earth-s-orbit-a-swiss-satellite-tackle/ |title=Cleaning up Earth's orbit: A Swiss satellite tackles space junk |publisher=EPFL |date=15 February 2012 |access-date=2013-04-03 |archive-url=https://web.archive.org/web/20130528112029/http://actu.epfl.ch/news/cleaning-up-earth-s-orbit-a-swiss-satellite-tackle/ |archive-date=28 May 2013 |url-status=live }}</ref> The mission has seen several evolutions to reach a pac-man inspired capture model.<ref>{{Cite web|url=https://www.cleanspaceone.ch|title=Space Debris Removal |website= Cleanspace One|access-date=2017-12-01|archive-url=https://web.archive.org/web/20171202052921/https://www.cleanspaceone.ch/|archive-date=2 December 2017|url-status=live}}</ref> In 2013, Space Sweeper with Sling-Sat (4S), a grappling satellite which captures and ejects debris was studied.<ref>{{cite web |last=Jan |first=McHarg |url=http://phys.org/news/2012-08-aims-space-debris.html |title=Project aims to remove space debris |publisher=Phys.org |date=10 August 2012 |access-date=2013-04-03 |archive-url=https://web.archive.org/web/20131005001405/http://phys.org/news/2012-08-aims-space-debris.html |archive-date=5 October 2013 |url-status=live }}</ref>{{update after|2019|12|22}} In 2022, a Chinese satellite, SJ-21, grabbed an unused satellite and "threw" it into an orbit with a lower risk for it to collide.<ref>{{cite news |title=Chinese 'space cleaner' spotted grabbing and throwing away old satellite {{!}} DW {{!}} 09.02.2022 |url=https://www.dw.com/en/chinese-space-cleaner-spotted-grabbing-and-throwing-away-old-satellite/a-60658574 |work=Deutsche Welle (www.dw.com)}}</ref><ref>{{cite news |last1=Gough |first1=Evan |title=A Chinese space tug just grappled a dead satellite |url=https://phys.org/news/2022-02-chinese-space-grappled-dead-satellite.html |access-date=12 February 2022 |work=Universe Today / phys.org |language=en}}</ref>

In December 2019, the European Space Agency awarded the first contract to clean up space debris. The €120 million mission dubbed [[ClearSpace-1]] (a spinoff from the EPFL project) is slated to launch in 2026. It aims to remove the 94&nbsp;kg [[PROBA-1]] satellite from orbit.<ref name="sn-20240424" /> A "chaser" will grab the junk with four robotic arms and drag it down to Earth's atmosphere where both will burn up.<ref name=guardian20191209>{{cite news |url=https://www.theguardian.com/science/2019/dec/09/european-space-agency-to-launch-clearspace-1-space-debris-collector-in-2025 |title=European Space Agency to launch space debris collector in 2025 |work=[[The Guardian]] |date=9 December 2019 |access-date=13 December 2019 |archive-url=https://web.archive.org/web/20191209182203/https://www.theguardian.com/science/2019/dec/09/european-space-agency-to-launch-clearspace-1-space-debris-collector-in-2025 |archive-date=9 December 2019 |url-status=live}}</ref>

==== Laser methods ====
The [[laser broom]] uses a ground-based [[laser]] to [[Ablation|ablate]] the front of the debris, producing a rocket-like thrust that slows the object. With continued application, the debris would fall enough to be influenced by atmospheric drag.<ref>Jonathan Campbell, [http://www.au.af.mil/au/awc/awcgate/cst/csat20.pdf "Using Lasers in Space: Laser Orbital Debris Removal and Asteroid Deflection"] {{Webarchive|url=https://web.archive.org/web/20101207230911/http://www.au.af.mil/au/awc/awcgate/cst/csat20.pdf |date=7 December 2010 }}, Occasional Paper No. 20, Air University, Maxwell Air Force Base, December 2000.</ref><ref name=wired20111026>{{cite news |last=Mann |first=Adam |title=Space Junk Crisis: Time to Bring in the Lasers |url=https://www.wired.com/wiredscience/2011/10/space-junk-laser/ |access-date=1 November 2011 |newspaper=Wired Science |date=26 October 2011 |archive-url=https://web.archive.org/web/20111029035748/http://www.wired.com/wiredscience/2011/10/space-junk-laser/ |archive-date=29 October 2011 |url-status=live }}</ref> During the late 1990s, the U.S. Air Force's Project Orion was a laser-broom design.<ref>Ivan Bekey, "[http://adsabs.harvard.edu/abs/1997ESASP.393..699B Project Orion: Orbital Debris Removal Using Ground-Based Sensors and Lasers].", ''Second European Conference on Space Debris'', 1997, ESA-SP 393, p. 699.</ref> Although a test-bed device was scheduled to launch on a Space Shuttle in 2003, international agreements banning powerful laser testing in orbit limited its use to measurements.<ref name=srdc20000816>Justin Mullins [https://archive.today/20130202170456/http://www.spaceref.com/news/viewpr.html?pid=2426 "A clean sweep: NASA plans to carry out a spot of housework."], ''New Scientist'', 16 August 2000.</ref> The 2003 [[Space Shuttle Columbia disaster|Space Shuttle ''Columbia'' disaster]] postponed the project and according to Nicholas Johnson, chief scientist and program manager for NASA's Orbital Debris Program Office, "There are lots of little gotchas in the Orion final report. There's a reason why it's been sitting on the shelf for more than a decade."<ref>Tony Reichhardt, [http://www.airspacemag.com/space-exploration/space_debris.html?c=y&page=2 "Satellite Smashers"] {{webarchive|url=https://archive.today/20120729012108/http://www.airspacemag.com/space-exploration/space_debris.html?c=y&page=2 |date=29 July 2012 }}, ''Air & Space Magazine'', 1 March 2008.</ref>

The momentum of the laser-beam [[photon]]s could directly impart a thrust on the debris sufficient to move small debris into new orbits out of the way of working satellites. NASA research in 2011 indicates that firing a laser beam at a piece of space junk could impart an impulse of {{convert|1|mm|abbr=on}} per second, and keeping the laser on the debris for a few hours per day could alter its course by {{convert|200|m|abbr=on}} per day.<ref name=UKmail20110316>{{cite journal | arxiv=1103.1690 | doi=10.1016/j.asr.2011.08.005 | title=Orbital debris–debris collision avoidance | date=2011 | last1=Mason | first1=James | last2=Stupl | first2=Jan | last3=Marshall | first3=William | last4=Levit | first4=Creon | journal=Advances in Space Research | volume=48 | issue=10 | pages=1643–1655 | bibcode=2011AdSpR..48.1643M }}</ref> One drawback is the potential for material degradation; the energy may break up the debris, adding to the problem.<ref>{{cite report|title=Space debris removalusing a high-power ground-basedlaser|author=David K. Monroe|url=https://www.osti.gov/servlets/purl/10121230|publisher=Sandia National Laboratories|access-date=March 30, 2023}}</ref> A similar proposal places the laser on a satellite in Sun-synchronous orbit, using a pulsed beam to push satellites into lower orbits to accelerate their reentry.<ref name=sn20141125 /> A proposal to replace the laser with an [[Ion Beam Shepherd]] has been made,<ref>C. Bombardelli and J. Peláez, "Ion Beam Shepherd for Contactless Space Debris Removal". ''Journal of Guidance, Control, and Dynamics'', Vol. 34, No. 3, May–June 2011, pp 916–920. http://sdg.aero.upm.es/PUBLICATIONS/PDF/2011/AIAA-51832-628.pdf {{Webarchive|url=https://web.archive.org/web/20120309094707/http://sdg.aero.upm.es/PUBLICATIONS/PDF/2011/AIAA-51832-628.pdf|date=9 March 2012}}.</ref> and other proposals use a foamy ball of [[aerogel]] or a spray of water,<ref>{{Cite news |last=Michaels |first=Daniel |date=March 11, 2009 |title=A Cosmic Question: How to Get Rid Of All That Orbiting Space Junk? |url=https://www.wsj.com/articles/SB123672891900989069 |access-date=2024-04-19 |work=Wall Street Journal |language=en-US}}</ref> inflatable balloons,<ref>[http://www.world-science.net/othernews/100804_spacejunk "Company floats giant balloon concept as solution to space mess"] {{Webarchive|url=https://web.archive.org/web/20110927074506/http://www.world-science.net/othernews/100804_spacejunk |date=27 September 2011 }}, Global Aerospace Corp press release, 4 August 2010.</ref> [[electrodynamic tether]]s,<ref>[http://www.star-tech-inc.com/id121.html "Space Debris Removal"] {{Webarchive|url=https://web.archive.org/web/20100816045757/http://www.star-tech-inc.com/id121.html |date=16 August 2010 }}, Star-tech-inc.com. Retrieved 18 July 2011.</ref> [[electroadhesion]],<ref name=mit20111005>{{cite news |last=Foust |first=Jeff |title=A Sticky Solution for Grabbing Objects in Space |url=http://www.technologyreview.com/computing/38774/#.To50S0SzPvk.twitter |archive-url=https://archive.today/20130204014735/http://www.technologyreview.com/computing/38774/%23.To50S0SzPvk.twitter |url-status=dead |archive-date=4 February 2013 |access-date=7 October 2011 |newspaper=MIT Technology Review |date=5 October 2011 }}</ref> and dedicated anti-satellite weapons.<ref>{{Cite news |last=Palmer |first=Jason |date=2011-08-09 |title=Space junk could be tackled by housekeeping spacecraft |url=https://www.bbc.com/news/science-environment-14405118 |access-date=2024-04-19 |work=BBC News |language=en-GB}}</ref>

==== Nets ====
On 28 February 2014, [[Japan Aerospace Exploration Agency]] (JAXA) launched a test "space net" satellite. The launch was an operational test only.<ref>{{Cite web |last=Roppolo |first=Michael |date=2014-02-28 |title=Japan launches net into space to help with orbital debris |url=https://www.cbsnews.com/news/japan-launches-net-into-space-to-help-with-orbital-debris/ |access-date=2024-04-19 |website=www.cbsnews.com |language=en-US}}</ref> In December 2016 the country sent a space junk collector via [[Kounotori 6]] to the ISS by which JAXA scientists experimented to pull junk out of orbit using a tether.<ref>{{cite web|title=Japan launching 'space junk' collector (Update)|url=https://phys.org/news/2016-12-japan-space-junk-collector.html|access-date=24 January 2017|archive-url=https://web.archive.org/web/20170202044407/https://phys.org/news/2016-12-japan-space-junk-collector.html|archive-date=2 February 2017|url-status=live}}</ref><ref>{{cite news|title=Japan launches 'space junk' collector|url=http://timesofindia.indiatimes.com/home/science/Japan-launches-space-junk-collector/articleshow/55904909.cms|newspaper=The Times of India|access-date=24 January 2017|archive-url=https://web.archive.org/web/20170208051124/http://timesofindia.indiatimes.com/home/science/Japan-launches-space-junk-collector/articleshow/55904909.cms|archive-date=8 February 2017|url-status=live}}</ref> The system failed to extend a 700-meter tether from a space station resupply vehicle that was returning to Earth.<ref>{{cite news|title=Space cargo ship experiment to clean up debris hits snag|url=http://www.japantimes.co.jp/news/2017/01/31/national/space-cargo-ship-experiment-clean-debris-hits-snag/|newspaper=The Japan Times Online|access-date=2 February 2017|date=31 January 2017|archive-url=https://web.archive.org/web/20170131183748/http://www.japantimes.co.jp/news/2017/01/31/national/space-cargo-ship-experiment-clean-debris-hits-snag/|archive-date=31 January 2017|url-status=live}}</ref><ref>{{cite web|title=A Japanese Space Junk Removal Experiment Has Failed in Orbit|url=http://www.space.com/35543-space-junk-japan-tether-experiment-space-station-htv.html|website=Space.com|date=February 2017|access-date=2 February 2017|archive-url=https://web.archive.org/web/20170201204947/http://www.space.com/35543-space-junk-japan-tether-experiment-space-station-htv.html|archive-date=1 February 2017|url-status=live}}</ref> On 6 February the mission was declared a failure and leading researcher Koichi Inoue told reporters that they "believe the tether did not get released".<ref>{{cite web|title=Japan's troubled 'space junk' mission fails|url=https://phys.org/news/2017-02-japan-space-junk-mission.html|access-date=12 February 2017|archive-url=https://web.archive.org/web/20170212091641/https://phys.org/news/2017-02-japan-space-junk-mission.html|archive-date=12 February 2017|url-status=live}}</ref>

Between 2012 and 2018, the European Space Agency was working on the design of a mission to remove large space debris from orbit using mechanical tentacles or nets. The mission, [[e.Deorbit]], had an objective to remove debris heavier than {{convert|4000|kg}} from LEO.<ref name="e.Deorbit">{{cite journal|url=https://conference.sdo.esoc.esa.int/proceedings/sdc7/paper/434/SDC7-paper434.pdf|title=Definition of an Automated Vehicle with Autonomous Fail-Safe Reaction Behavior to Capture and De-orbit Envisat|publisher=[[ESA]]|date=21 April 2017|access-date=16 January 2023|journal=7th European Conference on Space Debris|bibcode=2017spde.confE.101E |last1=Estable |first1=Stéphane |last2=Telaar |first2=Jürgen |last3=Lange |first3=Max |last4=Ahrns |first4=Ingo |last5=Pegg |first5=Katherine |last6=Jacobsen |first6=Dirk |last7=Gerrits |first7=Dennis |last8=Theybers |first8=Martijn |last9=Dayers |first9=Luc |last10=Vanden Bussche |first10=Simon |last11=Ilsen |first11=Stijn |last12=Debraekeleer |first12=Tom |last13=Lampariello |first13=Roberto |last14=Wygachiewicz |first14=Marcin |last15=Santos |first15=Nuno |last16=Canetri |first16=Marco |last17=Serra |first17=Pedro |last18=Soto Santiago |first18=Lucia |last19=Łukasik |first19=Artur |last20=Ratti |first20=John |last21=Puddephatt |first21=Dawn |last22=Rembala |first22=Richard |last23=Evans Brito |first23=Leanne |last24=Bondy |first24=Michel |last25=Biesbroek |first25=Robin |last26=Wolahan |first26=Andrew |page=101 }}</ref> Several capture techniques were studied, including a net, a harpoon, and a combination robot arm and clamping mechanism.<ref>Biesbroek, 2012 [http://space-env.esa.int/indico/getFile.py/access?resId=0&materialId=slides&confId=46 "Introduction to e.Deorbit"] {{Webarchive|url=https://web.archive.org/web/20140917225027/http://space-env.esa.int/indico/getFile.py/access?resId=0&materialId=slides&confId=46|date=17 September 2014}}. e.deorbit symposium. 6 May 2014.</ref> Funding of the mission was stopped in 2018 in favor of the [[ClearSpace-1]] mission, which is currently under development.

==== Harpoon ====
The [[RemoveDEBRIS]] mission plan is to test the efficacy of several ADR technologies on mock targets in low Earth orbit. In order to complete its planned experiments the platform is equipped with a net, a harpoon, a laser ranging instrument, a dragsail, and two [[CubeSat]]s (miniature research satellites).<ref name="sfn20180401">{{cite news|last1=Clark|first1=Stephen|title=Eliminating space junk could take step toward reality with station cargo launch|url=https://spaceflightnow.com/2018/04/01/eliminating-space-junk-could-take-step-toward-reality-with-station-cargo-launch/|access-date=6 April 2018|work=Spaceflight Now|date=1 April 2018|archive-url=https://web.archive.org/web/20180408050913/https://spaceflightnow.com/2018/04/01/eliminating-space-junk-could-take-step-toward-reality-with-station-cargo-launch/|archive-date=8 April 2018|url-status=live}}</ref> The mission was launched on 2 April 2018.<ref name="sfn20180404">{{cite news |url=https://spaceflightnow.com/2018/04/04/dragon-cargo-capsule-reaches-space-station-for-second-time/ |title=Dragon cargo capsule reaches space station for second time |work=Spaceflight Now |first=Stephen |last=Clark |date=4 April 2018 |accessdate=4 April 2018}}</ref>

====Recycling space debris====
Metal processing technologies to melt space debris and transform it into other useful form factors are developed by [[CisLunar Industries]]. Their system uses electromagnetic heating to melt metal and shape it into metal wire, sheet metal, and metal fuel.<ref name=jasi2022>{{cite web | last=Jasi | first=Amanda | title=From Junk to Fuel: Addressing the Space Debris Challenge | website=[[The Chemical Engineer]]| date=28 April 2022 | url=https://www.thechemicalengineer.com/features/from-junk-to-fuel-addressing-the-space-debris-challenge/ | access-date=25 July 2023}}</ref>

====Reusing space debris====

{{anchor|neumann}}<!---Neumann Drive will redirect here--->

A propulsion system dubbed the Neumann Drive has been developed in [[Adelaide]], [[South Australia]], and first sent into space in June 2023. Metal space junk is converted into [[fuel rod]]s, which can be plugged into the Neumann Drive, "basically converting the solid metal propellant into plasma". The Drive will be used by American space companies which already carry nets or robotic arms to capture orbital waste. The thruster enables these satellites to return to Earth with the waste they have collected, allowing it to be melted down to make more fuel.<ref name=alderson2023>{{cite web | last=Alderson | first=Bethanie | title=Space junk is causing clutter around the Earth, but a small cube could help cut back on trash | website=[[ABC News (Australia)]]| date=13 June 2023 | url=https://www.abc.net.au/news/2023-06-13/high-tech-cube-helping-solve-space-junk-problem/102469160 | access-date=11 July 2023}}</ref>

=== Barriers to dealing with debris===
With the rapid development of the computer and digitalization industries, more countries and companies have engaged in space activities since the turn of the 21st century. [[Tragedy of the commons|The tragedy of the commons]] is an economic theory referring to a situation where maximizing self-interest through using a shared resource can lead to the resource degradation shared by all.<ref name=":0">{{Cite journal |last=Taylor |first=Jared B. |date=2011 |title=Tragedy of the space commons: a market mechanism solution to the space debris problem |journal=The Columbia Journal of Transnational Law |volume=50 |pages=253–279}}</ref> Based on the theory, individuals' rational action in space will lead to an irrational collective result: orbits crowded with debris. As a [[common-pool resource]], the Earth's orbits, especially LEO and GEO that accommodate most satellites, are [[Excludability|nonexcludable]] and [[Rivalry (economics)|rivalrous]].<ref>{{Cite report |url=https://papers.ssrn.com/abstract=1586643 |title=A Tragedy of the Space Commons? |last=Chaddha |first=Shane |date=2010 |doi=10.2139/ssrn.1586643 |location=Rochester, New York |language=en-us |ssrn=1586643|url-access=subscription }}</ref>

To address the tragedy and ensure [[space sustainability]], many technical approaches have been developed. In terms of governance mechanisms, a top-down centralized one is less suitable to tackle the complex debris problem due to the increasing number of space actors.<ref name=":1">{{Cite journal |last1=Johnson-Freese |first1=Joan |last2=Weeden |first2=Brian |date=2012-01-27 |title=Application of Ostrom's Principles for Sustainable Governance of Common-Pool Resources to Near-Earth Orbit |url=http://dx.doi.org/10.1111/j.1758-5899.2011.00109.x |journal=Global Policy |volume=3 |issue=1 |pages=72–81 |doi=10.1111/j.1758-5899.2011.00109.x |issn=1758-5880|url-access=subscription }}</ref> Instead, a polycentric form of governance developed by [[Elinor Ostrom]] may work in space.<ref>{{Cite journal |last1=Morin |first1=Jean-Frédéric |last2=Richard |first2=Benjamin |date=2021-06-05 |title=Astro-Environmentalism: Towards a Polycentric Governance of Space Debris |url=http://dx.doi.org/10.1111/1758-5899.12950 |journal=Global Policy |volume=12 |issue=4 |pages=568–573 |doi=10.1111/1758-5899.12950 |s2cid=236171500 |issn=1758-5880|url-access=subscription }}</ref> In the process of promoting the polycentric network, there are some existing barriers needed to be dealt with.

==== Incomplete data of space debris ====
As orbital debris is a global problem affecting both spacefaring and non-spacefaring nations, it is necessary to be handled in a worldwide context.<ref name=":0" /> Because of the complexity and dynamics of object movements like spacecraft, debris, meteorites, etc., many countries and regions including the United States, Europe, Russia, and China have developed their [[space situational awareness]] (SSA) to avoid potential threats in space or plan actions in advance.<ref name=":2">{{Cite journal |last=Kaiser |first=Stefan A. |date=2015 |title=Legal and policy aspects of space situational awareness |url=http://dx.doi.org/10.1016/j.spacepol.2014.11.002 |journal=Space Policy |volume=31 |pages=5–12 |doi=10.1016/j.spacepol.2014.11.002 |bibcode=2015SpPol..31....5K |issn=0265-9646|url-access=subscription }}</ref> To an extent, SSA plays a role in tracking space debris. In order to build a powerful SSA system, there are two prerequisites: international cooperation and exchange of information and data.<ref name=":2" /> However, limitations exist in spite of the improving data quality over the past decades. Some space powers are not willing to share the information that they have collected, and those, such as the U.S., that have shared the data keep parts of it secret.<ref name=":3">{{Cite journal |last1=Lambach |first1=Daniel |last2=Wesel |first2=Luca |date=2021 |title=Tackling the Space Debris Problem: A Global Commons Perspective |journal=Proc. 8th European Conference on Space Debris|page=165 |bibcode=2021spde.confE.165L }}</ref> Instead of joining in a coordinated way, a great deal of SSA programs and national databases run parallel to each other with some overlaps, hindering the formation of a collaborative monitoring system.<ref name=":3" />

Some private actors are also trying to establish SSA systems. For example, the Space Data Association (SDA) formed in 2009 is a non-governmental entity. It currently consists of 21 global satellite operators and 4 executive members: [[Eutelsat]], [[Inmarsat]], [[Intelsat]], and [[SES (company)|SES]]. SDA is a non-profit platform, aiming to avoid radio interference and space collisions through pooling data from operators independently.<ref name=":2" /> Researchers suggest that it is essential to establish an international center for exchanging information on space debris because SSA networks do not completely equal debris tracking systems{{snd}}the former ones focus more on active and threatening objects in space.<ref name=":4">{{Cite journal |last=Skinner |first=Mark A. |date=2017 |title=Orbital debris: What are the best near-term actions to take? A view from the field |url=http://dx.doi.org/10.1016/j.jsse.2017.02.002 |journal=Journal of Space Safety Engineering |volume=4 |issue=2 |pages=105–111 |doi=10.1016/j.jsse.2017.02.002 |bibcode=2017JSSE....4..105S |issn=2468-8967|url-access=subscription }}</ref> In terms of debris populations and defunct satellites, few operators have provided data.<ref name=":4" />

In a polycentric governance network, a resource that cannot be holistically monitored is less likely to be well managed.<ref name=":3" /> Both insufficient transnational cooperation and information sharing bring resistance to addressing the debris problem. There is a long way to go to build a global network that covers complete data and has strong interconnection and interoperability.

==== Insufficient participation of private actors ====
With the commercialization of satellites and space, the private sector is getting more interested in space activities. For example, [[SpaceX]] is planning to create a network of around 12,000 small satellites that can transmit high-speed internet to any place in the world.<ref>{{Cite web |last=Sheetz |first=Michael |date=2020-08-10 |title=SpaceX is manufacturing 120 Starlink internet satellites per month |url=https://www.cnbc.com/2020/08/10/spacex-starlink-satellte-production-now-120-per-month.html |access-date=2022-03-14 |website=CNBC |language=en}}</ref> The proportion of commercial spacecraft has increased from 4.6% in the 1980s to 55.6% in the 2010s.<ref>{{Cite book |title=The Space Economy in Figures: How Space Contributes to the Global Economy |url=https://www.oecd-ilibrary.org/science-and-technology/the-space-economy-in-figures_c5996201-en |access-date=2022-03-14 |via=www.oecd-ilibrary.org |year=2019 |language=en |doi=10.1787/c5996201-en|isbn=9789264696549 |s2cid=242966859 }}</ref> Despite the high participation rate of commercial entities, [[United Nations Committee on the Peaceful Uses of Outer Space|UN COPUOS]] once deliberately excluded them from having a voice in discussions unless being formally invited by a member state.<ref name=":1" /> Ostrom said that the involvement of all relevant stakeholders in the rule-design and implementation process is one of the critical elements of successful governance.<ref>{{Cite web |last1=Chow |first1=Tiffany |last2=Weeden |first2=Brian C. |date=2013 |title=Engaging All Stakeholders in Space Sustainability Governance Initiatives |url=https://swfound.org/media/119718/iac-13,e3,4,2,x18131_tc.pdf |website=swfound.org}}</ref> The exclusion of private actors largely reduces the effectiveness of the committee's role in making collective-choice arrangements that reflect the interests of all space users.<ref name=":1" />

The limited engagement of private actors slows the process of addressing space debris.<ref name=":5">{{Cite journal |last=Williamson |first=Ray A. |date=2012 |title=Assuring the sustainability of space activities |url=http://dx.doi.org/10.1016/j.spacepol.2012.06.010 |journal=Space Policy |volume=28 |issue=3 |pages=154–160 |doi=10.1016/j.spacepol.2012.06.010 |bibcode=2012SpPol..28..154W |issn=0265-9646|url-access=subscription }}</ref> Ties between dissimilar stakeholders in the governance network offer access to diverse resources.<ref name=":6">{{Cite book |last=Evans |first=J. P. |title=Environmental Governance |publisher=Taylor & Francis |year=2011 |location=Hoboken |language=en-us}}</ref> Different competence among stakeholders can help allocate the tasks more reasonably. In that case, the expertise and experience of private operators are critical to help the world achieve space sustainability.<ref name=":5" /> The complementary strengths of different stakeholders enable the governance network to be more adaptable to changes and reach common goals more effectively.<ref name=":6" /> In recent years, many private actors have seen commercial opportunities of eliminating space debris. It is estimated that by 2022 the global market for debris monitoring and removal will generate a revenue of around $2.9 billion.<ref>{{Cite web |last=Research and Markets |date=2018 |title=Global Space Debris Monitoring and Removal Market 2018-2022 with Airbus, ASTROSCALE, Boeing, Lockheed Martin, Northrop Grumman & RSC Energia Dominating |url=https://www.prnewswire.com/news-releases/global-space-debris-monitoring-and-removal-market-2018-2022-with-airbus-astroscale-boeing-lockheed-martin-northrop-grumman--rsc-energia-dominating-300697457.html |access-date=2022-03-14 |website=www.prnewswire.com |language=en}}</ref> For example, [[Astroscale]] has contracted with European and Japanese space agencies to develop the capacity of removing orbital debris.<ref>{{Cite web |last1=Moore |first1=Adrian |last2=van Burken |first2=Rebecca |date=2021 |title=As Commercial Space Travel Becomes Reality, Debris and Space Traffic Management Becomes More Important |url=https://reason.org/commentary/as-commerical-space-travel-becomes-reality-debris-and-space-traffic-management-becomes-more-important/ |access-date=2022-03-14 |website=Reason Foundation |language=en-US}}</ref> Despite that, they are still in small quantity compared to the number of those who have placed satellites in space. [[Privateer Space]], a Hawaiian-based startup company by American engineer [[Alex Fielding]], space environmentalist [[Moriba Jah]], and [[Apple Inc.|Apple]] co-founder [[Steve Wozniak]], announced plans in September 2021 to launch hundreds of satellites into orbit in order to study space debris.<ref name="space.com">{{Cite web |author1=Wall |first=Mike |date=2021-11-18 |title=Steve Wozniak's startup Privateer plans to launch hundreds of satellites to study space debris |url=https://www.space.com/steve-wozniak-privateer-hundreds-satellites-space-debris |access-date=2022-04-28 |website=Space.com |language=en-us}}</ref> However, the company stated it is in "stealth mode" and no such satellites have been launched.<ref name="space.com"/>

Fortunately, the current space exploration is not completely driven by competition, and there still exists a chance for dialogues and cooperation among all stakeholders in both developed and developing countries, to reach an agreement on tackling space debris and assure an equitable and orderly exploration.<ref>{{Cite journal |last1=Newman |first1=Christopher J. |last2=Williamson |first2=Mark |date=2018 |title=Space Sustainability: Reframing the Debate |url=http://dx.doi.org/10.1016/j.spacepol.2018.03.001 |journal=Space Policy |volume=46 |pages=30–37 |doi=10.1016/j.spacepol.2018.03.001 |bibcode=2018SpPol..46...30N |s2cid=158678917 |issn=0265-9646}}</ref> Besides private actors, [[network governance]] does not necessarily exclude the states from playing a role. Instead, the different functions of states might promote the governance process.<ref>{{Cite journal |last1=Carlsson |first1=Lars Gunnar |last2=Sandström |first2=Annica Charlotte |date=2007 |title=Network Governance of the Commons |journal=International Journal of the Commons |volume=2 |issue=1 |pages=33–54 |doi=10.18352/ijc.20 |s2cid=155049248 |issn=1875-0281|doi-access=free |bibcode=2007IJCom...2...33C |hdl=10535/1749 |hdl-access=free }}</ref> To improve the polycentric governance network of space debris, researchers suggest: encourage data-sharing among different national and organizational databases at the political level; develop shared standards for data collection systems to improve interoperability; and enhance the participation of private actors through involving them in national and international discussions.<ref name=":3" />

==On other celestial bodies==
[[File:PIA25219-MarsIngenuityHelicopter-Backshell-20220419.jpg|thumb|upright=1.2|''Perseverance'''s backshell sitting upright on the surface of Jezero Crater]]

The issue of space debris has been raised as a mitigation challenge for missions around the Moon with the danger of increasing space debris around it.<ref name="Carter 2022">{{cite web | last=Carter | first=Jamie | title=As Chinese Rocket Strikes Moon This Week We Need To Act Now To Prevent New Space Junk Around The Moon Say Scientists | website=Forbes | date=2022-02-27 | url=https://www.forbes.com/sites/jamiecartereurope/2022/02/27/as-chinese-rocket-strikes-moon-this-week-we-need-to-act-now-to-prevent-new-space-junk-around-the-moon-say-scientists/ | access-date=2022-04-09}}</ref><ref name="Nast 2013">{{cite magazine | title=Space: The Final Frontier of Environmental Disasters? | magazine=Wired | date=15 July 2013 | url=https://www.wired.com/2013/07/space-environmentalism/ |first=Adam|last=Mann|access-date=21 January 2023}}</ref>

It is thought that on 4 March 2022, for the first time, human space debris—most likely a spent [[rocket body]], [[Long March 3C]] third stage from the 2014 [[Chang'e 5-T1|Chang'e 5 T1]] mission—unintentionally [[Hertzsprung (crater)#2022 Long March 3C third stage impact|hit the lunar surface]], creating an unexpected double crater.<!--List of artificial objects on the Moon--><ref>{{cite news |last1=Strickland |first1=Ashley |last2=Hunt |first2=Katie |title=New double crater seen on the moon after mystery rocket impact |url=https://edition.cnn.com/2022/06/27/world/rocket-moon-impact-crater-scn/index.html |access-date=13 July 2022 |work=CNN}}</ref><ref>{{cite web |last1=Garner |first1=Rob |title=Rocket Impact Site on Moon Seen by NASA's Lunar Reconnaissance Orbiter |url=https://www.nasa.gov/feature/goddard/2022/nasas-lunar-reconnaissance-orbiter-spots-rocket-impact-site-on-moon |website=NASA |access-date=13 July 2022 |date=23 June 2022}}</ref>

In 2022, several elements of space debris were found on Mars: ''[[Perseverance (rover)|Perseverance]]'''s backshell was found on the surface of Jezero Crater,<ref>{{cite web |last=Lenberg |first=Tatum |date=29 April 2022 |title=New Photos of Martian Space Wreckage |url=https://www.discovery.com/space/martian-space-wreckage |access-date=21 January 2023 |website=Discovery |publisher=Discovery.com |language=en}}</ref> and a piece of a thermal blanket which may have come from the descent stage of the rover.<ref>{{cite web |last1=Kooser |first1=Amanda |title='Unexpected': NASA Mars Rover Finds Piece of Its Landing System Stuck on a Rock |url=https://www.cnet.com/science/space/unexpected-nasa-mars-rover-finds-shiny-foil-piece-on-a-rock/ |access-date=3 August 2022 |website=CNET |language=en}}</ref><ref>{{cite web |last=Devlin |first=Hannah |date=16 June 2022 |title=Nasa rover sighting reignites fears about human space debris |url=https://www.theguardian.com/science/2022/jun/16/nasa-rover-sighting-reignites-fears-about-human-space-debris |access-date=21 January 2023 |website=the Guardian |language=en}}</ref>

{{As of|2024|February}}, [[Mars]] is littered with about seven tons of human-made debris. Most of it consists of crashed and inactive spacecraft as well as discarded components.<ref>{{Cite web |last=Kilicpublished |first=Cagri |date=2022-09-28 |title=Mars is littered with 15,694 pounds of human trash from 50 years of robotic exploration |url=https://www.space.com/mars-littered-with-human-trash |access-date=2024-04-04 |website=Space.com |language=en-us}}</ref><ref>{{Cite web |title=Humans have already dumped 7 tonnes of junk on Mars, map reveals |url=https://www.wionews.com/science/map-shows-human-made-debris-piling-up-on-mars-over-seven-tonnes-of-space-junk-lying-around-red-planet-686201 |access-date=2024-04-04 |website=WION |date=2 February 2024 |language=en-us}}</ref>

==In popular culture==
<!-- Popular culture references should be from [[WP:RS|secondary sources]], not primary sources, and the source should support the notability of the space debris connection. -->

''[[Until the End of the World]]'' (1991) is a French sci-fi drama set under the backdrop of an out-of-control Indian nuclear satellite, predicted to re-enter the atmosphere, threatening vast populated areas of the Earth.<ref>{{Cite news |last=Adams |first=Eric |date=21 April 2020 |title=This 30-Year-Old Sci-Fi Epic Is a Saga for Our Times |url=https://www.wired.com/story/until-the-end-of-the-world/ |department=Culture |magazine=[[Wired (magazine)|Wired]] |issn=1059-1028 |access-date=2020-06-19 |language=en-us}}</ref>

''[[Gravity (2013 film)|Gravity]]'', a 2013 survival film directed by [[Alfonso Cuarón|Alfonso Cuaron]], is about a disaster on a space mission caused by Kessler syndrome.<ref>{{Cite news|last=Sinha-Roy|first=Piya|date=21 July 2013|title='Gravity' gets lift at Comic-Con as director Cuaron leaps into space |publisher=[[Reuters]] |url=https://www.reuters.com/article/comiccon-film-gravity/gravity-gets-lift-at-comic-con-as-director-cuaron-leaps-into-space-idUSL1N0FQ0EV20130721|access-date=9 June 2020}}</ref>

In season 1 of ''[[Love, Death & Robots]]'' (2019), episode 11, "Helping Hand", revolves around an astronaut being struck by a screw from space debris which knocks her off a satellite in orbit.<ref>{{Cite web|last=Brady|first=Matt|date=July 3, 2019|title=Conservation of Momentum in Netflix's Love, Death & Robots|url=https://thescienceof.org/can-throwing-your-hand-away-really-help-you-move-in-space-conservation-of-momentum-says-yes/|access-date=2021-04-21|website=The Science Of|language=en-US}}</ref>

Manga and anime ''[[Planetes]]'' tells a story about a crew of Space Debris station that collects and disposes of space debris.<ref>{{cite web|author1=Foxe, Steve|author2=Edgar, Sean|author3=The Paste Comics Crew|title=Required Reading: 50 of the Best Sci-Fi Comics|url=https://www.pastemagazine.com/comics/required-reading/required-reading-70-of-the-best-sci-fi-comics/?p=4|publisher=[[Paste (magazine)|Paste]]|access-date=January 25, 2022|archive-url=https://web.archive.org/web/20220125164453/https://www.pastemagazine.com/comics/required-reading/required-reading-70-of-the-best-sci-fi-comics/?p=4|archive-date=January 25, 2022|date=January 6, 2017|url-status=live}}</ref>

Beside space debris as an issue of science-fiction stories other stories feature it as a reservoir for the story, as in stories about space junk scavengers like ''[[Space Sweepers]]'' (2021), or as a result or environment of the story.

The episode ''Conflict'' from Gerry and Sylvia Anderson's [[UFO (British TV series)|''U.F.O.'']] sci-fi TV series shows how small alien spaceships could use Terrestrial space debris such as orbital boosters to become undetectable by ''SHADO'''s orbital ''Space Intruder Detector'' (''S.I.D.'').<ref>{{cite web|title=U.F.O Season 1 Episode 4: Conflict |url=https://www.imdb.com/title/tt0735620/ |access-date=April 6, 2025|website=IMDB.com}}</ref>

== See also ==
{{Portal|Space}}
{{Div col|colwidth=20em}}
* [[:Category:Derelict satellites]]
* [[Interplanetary contamination]]
* [[Liability Convention]]
* [[List of large reentering space debris]]
* [[List of space debris producing events]]
* [[Long Duration Exposure Facility]]
* [[Near-Earth object]]
* [[Orbital Debris Co-ordination Working Group]]
* [[Project West Ford]]
* [[Satellite warfare]]
* [[Solar Maximum Mission]]
* [[Spacecraft cemetery]]
* [[Space domain awareness]]
* [[Space sustainability]]
{{Div col end}}

== References ==
=== Citations ===
{{Reflist}}

=== Bibliography ===
{{Refbegin}}
* {{cite report|last=Gleghorn |first=George|date=1995|title=Orbital Debris: A Technical Assessment|url=https://orbitaldebris.jsc.nasa.gov/library/a-technical-assessment.pdf|publisher=National Academy of Sciences|isbn=0-309-05125-8|display-authors=etal}}.
* {{cite journal |last1=Hoots |first1=Felix |last2=Schumacher|first2 = Paul Jr. |last3=Glover |first3=Robert A. |year=2004| title = History of Analytical Orbit Modeling in the U.S. Space Surveillance System |journal=Journal of Guidance, Control, and Dynamics | volume=27 |issue= 2| pages= 174–185 |doi=10.2514/1.9161| bibcode = 2004JGCD...27..174H}}
* {{cite journal|last=Johnson|first=Nicholas L.|title=Monitoring and Controlling Debris in Space|journal=Scientific American|volume=279|number=2|year=1998|pages=62–67|doi=10.1038/scientificamerican0898-62 |jstor=26070599 |bibcode=1998SciAm.279b..62J |url=http://www.jstor.org/stable/26070599|access-date=21 January 2023|url-access=subscription}}.
* {{cite journal|last=Kessler|first=Donald|year=1971 |url=http://adsabs.harvard.edu/abs/1971NASSP.267..595K|title=Estimate of Particle Densities and Collision Danger for Spacecraft Moving Through the Asteroid Belt|journal=Physical Studies of Minor Planets|volume=267 |publisher=NASA SP-267|pages=595–605 |bibcode=1971NASSP.267..595K}}.
* {{cite journal|last1=Kessler|first1=Donald |last2=Cour-Palais|first2=Burton |date=June 1978|url=http://webpages.charter.net/dkessler/files/Collision%20Frequency.pdf |title=Collision Frequency of Artificial Satellites: The Creation of a Debris Belt|journal=Journal of Geophysical Research|volume=81|number=A6 |pages=2637–46|bibcode=1978JGR....83.2637K|doi=10.1029/JA083iA06p02637|archive-url=https://web.archive.org/web/20110515132446/http://webpages.charter.net/dkessler/files/Collision%20Frequency.pdf |archive-date=15 May 2011 }}.
* {{cite journal|last=Kessler|first=Donald|year=1981 |title=Sources of Orbital Debris and the Projected Environment for Future Spacecraft|url=http://webpages.charter.net/dkessler/files/SourcesofOrbitalDebris.pdf |journal=Journal of Spacecraft|volume=16|number=4|pages=357–60|doi=10.2514/3.57828 |bibcode=1981JSpRo..18..357K |archive-url=https://web.archive.org/web/20100714011725/http://webpages.charter.net/dkessler/files/SourcesofOrbitalDebris.pdf |archive-date=14 July 2010 }}.
* {{cite journal|last=Kessler|first=Donald|date=December 1991 |title=Collisional Cascading: The Limits of Population Growth in Low Earth Orbit |url=http://webpages.charter.net/dkessler/files/Critical%20Density%201991.pdf |journal=Advances in Space Research|volume=11 |number=12 |pages=63–66|doi=10.1016/0273-1177(91)90543-S |bibcode=1991AdSpR..11l..63K |archive-url=https://web.archive.org/web/20100714011651/http://webpages.charter.net/dkessler/files/Critical%20Density%201991.pdf |archive-date=14 July 2010 }}.
* {{cite journal|last1=Kessler|first1=Donald |last2=Anz-Meador|first2=Phillip|date=March 2001|url= https://conference.sdo.esoc.esa.int/proceedings/sdc3/paper/97/SDC3-paper97.pdf|title=Critical Number of Spacecraft in Low Earth Orbit: Using Fragmentation Data to Evaluate the Stability of the Orbital Debris Environment|journal=Proceedings of the Third European Conference on Space Debris|location=Darmstadt Germany|access-date=January 21, 2023}}.
* {{cite book|last=Kessler|first=Donald|date=8 March 2009 |url=https://aquarid.physics.uwo.ca/kessler/KesSym.html|title=The Kessler Syndrome|publisher=Western University Canada|access-date=January 21, 2023}}.
* {{cite journal|last=Liou |first=J.-C.|date=January 14, 2020|title=Risks from Orbital Debris and Space Situational Awareness|journal=IAA Conference on Space Situational Awareness|location=Washington, D.C. |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20200000450.pdf|access-date=January 21, 2023}}.
* {{cite magazine |last=Schefter |first=Jim |date=July 1982 |volume=221 |issue=1 |url=https://books.google.com/books?id=q0qVc8dQrpgC&pg=PA48 |title=The Growing Peril of Space Debris |magazine=[[Popular Science]] |pages=48–51 |via=Google Books }}.
{{Refend}}

== Further reading ==
{{Refbegin}}
* [https://web.archive.org/web/20050901043047/http://www.aero.org/capabilities/cords/debris-basics.html "What is Orbital Debris?"], Center for Orbital and Reentry Debris Studies, [[Aerospace Corporation]]
* {{cite book |title=Limiting Future Collision Risk to Spacecraft: An Assessment of NASA's Meteoroid and Orbital Debris Programs |author=Committee for the Assessment of NASA's Orbital Debris Programs |year=2011 |publisher=[[United States National Research Council|National Research Council]] |location=Washington, D.C. |isbn=978-0-309-21974-7 |url=http://www.nap.edu/openbook.php?record_id=13244 }}
** {{cite news |url=https://www.reuters.com/article/us-space-debris-idUSTRE7805VY20110901 |title=Space junk reaching 'tipping point,' report warns |first1= Irene |last1=Klotz|date=1 September 2011 |work=Reuters |access-date=2 September 2011}} News item summarizing the above report
* Steven A. Hildreth and Allison Arnold. [https://fas.org/sgp/crs/natsec/R43353.pdf ''Threats to U.S. National Security Interests in Space: Orbital Debris Mitigation and Removal.''] Washington, D.C.: [[Congressional Research Service]], 8 January 2014.
* David Leonard, "The Clutter Above", ''Bulletin of the Atomic Scientists'', July/August 2005.
* Patrick McDaniel, [https://apps.dtic.mil/sti/pdfs/ADA331517.pdf "A Methodology for Estimating the Uncertainty in the Predicted Annual Risk to Orbiting Spacecraft from Current or Predicted Space Debris Population"]. National Defense University, 1997.
* [http://orbitaldebris.jsc.nasa.gov/library/IAR_95_Document.pdf "Interagency Report on Orbital Debris, 1995"], National Science and Technology Council, November 1995.
* Nickolay Smirnov, [https://books.google.com/books?id=FoSOD7fRdjA ''Space Debris: Hazard Evaluation and Mitigation'']. Boca Raton, FL: CRC Press, 2002, {{ISBN|0-415-27907-0}}.
* Richard Talcott, "How We Junked Up Outer Space", ''[[Astronomy (magazine)|Astronomy]]'', Volume 36, Issue 6 (June 2008), pp.&nbsp;40–43.
* [http://www.unoosa.org/pdf/reports/ac105/AC105_720E.pdf "Technical report on space debris, 1999"], United Nations, 2006. {{ISBN|92-1-100813-1}}.
* {{cite book |title=Active Debris Removal in Space: How to Clean the Earth's Environment from Space Debris |author=Robin Biesbroek |year=2015 |publisher=CreateSpace |isbn=978-1-5085-2918-7 |url=https://www.createspace.com/5324190 }}
* [[Raffi Khatchadourian|Khatchadourian, Raffi]], "The Trash Nebula: Millions of man-made artifacts are circling Earth. Will one of them cause a disaster?", 28 September 2020, pp.&nbsp;44–52, 54–55. "By one estimate, there are a hundred million bits of debris that are a millimetre in size, a hundred million as small as a micron. We live in a corona of trash. [T]he problem, if ignored, could destroy all the [[satellite]]s that orbit near the Earth – a loss that would be more acutely felt as humanity increasingly relied on space." (p.&nbsp;47.)
{{Refend}}

== External links ==
{{Commons|Space debris}}
{{Div col}}

* [https://www.worldsciencefestival.com/infographics/space-junk-infographic/ Sorting Through Our Space Junk: Space Junk Infographic]
* [https://www.satview.org/?sat_id= Sativew – Tracking Space Junk in real time]
* [https://www.orbitaldebris.jsc.nasa.gov/ NASA Orbital Debris Program Office]
* [http://celestrak.org/SOCRATES/ SOCRATES: A free daily service predicting close encounters on orbit between satellites and debris orbiting Earth]
* [http://www.astronomycast.com/2008/03/ep-82-space-junk/ Space Junk] ''[[Astronomy Cast]]'' episode No. 82 (2008?), includes full transcript

{{div col end}}

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