View source for Apollo Telescope Mount

{{Short description|Solar observatory on Skylab}}
{{use mdy dates|date=September 2021}}
{{Infobox telescope}}
[[File:Apollo Telescope Mount Solar Array 7023006.jpg|thumb|Solar array for the ATM (could also power other Skylab systems)]]
<!--[[File:Skylab Station Viewed by Skylab 2 Command Module - GPN-2000-001709.jpg|thumb|right|250px|Image taken during the Skylab 2 inspection of Skylab, showing the ATM in position. The main solar panel on Skylab is not yet deployed and the micrometeoroid shield is missing]]-->
The '''Apollo Telescope Mount''', or '''ATM''', was a crewed [[Sun|solar]] [[observatory]] that was a part of [[Skylab]], the first American [[space station]]. It could observe the Sun in wavelengths ranging from soft X-rays, ultraviolet, and visible light.

The ATM was manually operated by the astronauts aboard Skylab from 1973&ndash;74, yielding data principally as exposed [[photographic film]] that was returned to Earth with the crew. The film magazines had to be changed out by the crew during [[extra-vehicular activity|spacewalks]], although some instruments had a live video feed that could be observed from inside the space station. Some of the first [[Polaroid Corporation|Polaroid]] photos (an [[instant film]]-to-hard copy camera) in space were taken of a Skylab CRT [[Electronic visual display|video screen]] displaying the Sun as recorded by an ATM instrument. Although the ATM was integrated with the Skylab station, it started as a separate project related to use of the Apollo spacecraft, which is why it has the name Apollo in it rather than Skylab; the Skylab station was visited by astronauts using the Apollo spacecraft launched by the [[Saturn IB]], and the Station with its solar observatory was launched by a [[Saturn V]].

The ATM was designed and construction was managed at [[NASA]]'s [[Marshall Space Flight Center]].<ref>{{cite web|url=http://www.nasm.si.edu/spacecraft/SS-ATM.htm |title=NASM Space Artifacts: Apollo Telescope Mount |date=2006-09-16 |access-date=2016-02-27 |url-status=dead |archive-url=https://web.archive.org/web/20060916073735/http://www.nasm.si.edu/spacecraft/SS-ATM.htm |archive-date=September 16, 2006 }}</ref> It included eight major observational instruments, along with several lesser experiments.

ATM was integrated with the Skylab space station, which was used to point the observatory. Likewise, Skylab used power from the ATM solar arrays.

As of 2006, the original exposures were on file (and accessible to interested parties) at the [[Naval Research Laboratory]] in [[Washington, D.C.]]

==Design==
The ATM was actively cooled to maintain the temperature of the instruments within a certain range.<ref name="Apollo Telescope Mount">{{Cite web|url=http://wwwsolar.nrl.navy.mil/skylab_atm.html|title=Apollo Telescope Mount|website=wwwsolar.nrl.navy.mil|access-date=2018-07-10|archive-url=https://web.archive.org/web/20171107060638/http://wwwsolar.nrl.navy.mil/skylab_atm.html|archive-date=2017-11-07|url-status=dead}}</ref> Pointing was done with the help of the Skylab computer, which could be commanded from the space station by astronauts or by communication link from Earth.<ref name="Apollo Telescope Mount"/> The four external mounted solar panels deploy in an 'X' shape, and provide around 30% of the station's electrical power.

{|
|-
|[[File:Skylab Apollo Telescope Mount Spar and Sun End 7026490.jpg|thumb|left|Sun facing end showing the instrumentation apertures]]
|[[File:Apollo Telescope Mount Spar Assembly 6903725.jpg|thumb|A side view of the instrument cluster without its enclosure]]
|[[File:Apollo Telescope Mount Spar Unit 7026763.jpg|thumb|ATM assembly]]
|}

==History==
<!--[[File:Owen Garriott at the Apollo Telescope Mount console.jpg|thumb|left|Skylab 3 (2nd crewed mission) science pilot [[Owen Garriott]] at the ATM console]] -->
[[File:Skylab 2 Weitz at Apollo Telescope Mount control panel.jpg|thumb|Astronaut [[Paul J. Weitz]] at the telescope's command and display (C&D) console inside Skylab during the mission (June 1973)<ref>{{cite web |url=http://spaceflight.nasa.gov/gallery/images/skylab/skylab2/html/sl2-x9-747.html |title=Photo-sl2-x9-747 |website=spaceflight.nasa.gov |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20141228033737/http://spaceflight.nasa.gov/gallery/images/skylab/skylab2/html/sl2-x9-747.html |archive-date=28 December 2014 |url-status=dead}}</ref>]]

The ATM was one of the projects that came out of the late 1960s [[Apollo Applications Program]], which studied a wide variety of ways to use the infrastructure developed for the [[Apollo program]] in the 1970s. Among these concepts were various extended-stay lunar missions, a permanent lunar base, long-duration space missions, a number of large observatories, and eventually the "[[wet workshop]]" space station.

In the case of the ATM, the initial idea was to mount the instrumentation in a deployable unit attached to the [[Apollo Command/Service Module|Service Module]],<ref>{{cite web |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770081341_1977081341.pdf |title=Archived copy |website=ntrs.nasa.gov |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20100518075300/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770081341_1977081341.pdf |archive-date=18 May 2010 |url-status=dead}}</ref> this was then changed to use a modified [[Apollo Lunar Module]]<ref>{{cite web |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790073384_1979073384.pdf |title=Archived copy |website=ntrs.nasa.gov |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20100521102900/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790073384_1979073384.pdf |archive-date=21 May 2010 |url-status=dead}}</ref> to house controls, observation instruments and recording systems, while the lunar descent stage was replaced with a large solar telescope and solar panels to power it all. After launch, it would be met in orbit by a three-crew Apollo CSM who would operate it and retrieve data before returning to Earth. As many of the other concepts were dropped, eventually only the space station and ATM remained "on the books". The plans then changed to launch the ATM and have it connect to Skylab in orbit. Both spacecraft would then be operated by the Skylab crews.

With the cancellation of the later Apollo landing missions providing a Saturn V, the wet workshop concept was no longer needed. Instead, the plans were changed to orbit an expanded, dry version of the station. The ATM would now be launched attached to the station, as the Saturn V had enough power to launch them both at the same time. This change saved the Skylab program when a problem during launch destroyed one of the workshop solar panels and prevented the other from automatically deploying. The windmill-like arrays on the ATM, which fed power to both the ATM and the station, remained undamaged due to the protection within the launch shroud, and provided enough power for crewed operations until the one remaining workshop array could be deployed during the first crewed mission.

There were additional astronomical and Earth observation experiments aboard Skylab. During development, the ATM was subjected to thermal vacuum testing.<ref>[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720011230.pdf APOLLO TELESCOPE  MOUNT THERMAL SYSTEMS UNIT THERMAL VACUUM  TEST ]</ref>

[[File:Deployment of Apollo Telescope Mount.jpg|thumb|left|Illustration of the telescope cluster and solar array deployment]]

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==Instruments==
[[File:Skylab IV-view of telescope.jpg|thumb|right|250px|Image of the ATM taken showing some of the instrument covers]]

There were 8 major solar studies instruments on the mount.<ref name=halpha>{{cite web |url=http://mix.msfc.nasa.gov/abstracts.php?p=1320 |title=0101909 - H-Alpha #1 Telescope - Skylab Apollo Telescope Mount |website=Mix.msfc.nasa.gov |date=1973-01-01 |access-date=2016-02-27 |archive-url=https://web.archive.org/web/20150428225347/https://mix.msfc.nasa.gov/abstracts.php?p=1320 |archive-date=2015-04-28 |url-status=dead }}</ref><ref name=chap4>{{cite web|url=https://history.nasa.gov/SP-402/ch4.htm |title=ch4 |website=History.nasa.gov |date=1973-05-14 |access-date=2016-02-27}}</ref> Combined, they could observe the Sun in light wavelengths from 2 to 7000 Å ([[Angstrom|angstroms]]), which corresponds to [[soft X-ray]], [[ultraviolet]], and [[visible light]].<ref name=chap4/>

*two [[X-ray telescope|X-ray telescopes]]<ref name=chap4/>
*extreme ultraviolet [[spectroheliograph]]<ref name=chap4/>
*ultraviolet spectroheliometer<ref name=chap4/>
*ultraviolet [[spectrograph]]<ref name=chap4/>
*visible light [[coronagraph]]<ref name=chap4/>
*two [[H-alpha|Hydrogen Alpha]] telescopes<ref name=halpha/>

Same instruments by designation:

The X-Ray instruments included:<ref name="ReferenceA"/>
*S-054
*S-056
*S-020 (X-ray and [[extreme ultraviolet]] camera)<ref name="ReferenceA"/>
UV instruments included:<ref name="ReferenceA"/>
*S-082A (Extreme ultraviolet spectroheliograph)
*S-082B (Ultraviolet spectroheliometer)
*S-055 (Ultraviolet spectrograph)
[[Hydrogen-alpha|Hydrogen alpha]] and coronograph:
*H-alpha no. 1
*H-alpha no. 2
*S-052 (a Coronagraph)

Also, experiment S149 was attached to one of the ATM solar panels.<ref>{{cite web| url = https://www.nasa.gov/topics/history/features/skylab2.html| title = Owen Garriott Performs a Spacewalk During Skylab 3 {{!}} NASA| date = March 11, 2015}}</ref>

==Film canisters==

Six ATM experiments used film to record data, and over the course of the missions over 150,000 successful exposures were recorded.<ref name="history.nasa.gov">{{Cite web|url=https://history.nasa.gov/SP-402/ch4.htm|title=ch4|website=history.nasa.gov|access-date=2017-01-09}}</ref> The film canister had to be manually retrieved on crewed spacewalks to the instruments during the missions.<ref name="history.nasa.gov"/> The film canisters were returned to Earth aboard the Apollo capsules when each mission ended, and were among the heaviest items that had to be returned at the end of each mission.<ref name="ReferenceA">{{Cite web|url=https://history.nasa.gov/SP-402/ch4.htm|title=Ch4}}</ref> The heaviest canisters weighed 40&nbsp;kg (88.1 lb) and could hold up to 16,000 frames of film.<ref name="ReferenceA"/>

Over the course of operations almost 30 canisters were loaded and utilized, and then returned to Earth.<ref>{{Cite web|url=https://history.nasa.gov/SP-402/ch4.htm|title=ch4|website=history.nasa.gov|access-date=2018-07-10}}</ref>  
<!--{{-}}-->

==Results==
<gallery>
File:Solar eruption in 1973 seen by Skylab 2 (S73-33788).jpg|Solar eruption seen in this spectroheliograph covering the wavelength region from 150 to 650 angstroms ([[Skylab 2]], June 10, 1973)
File:S74-15583skylabsunview.jpg|Extreme ultraviolet image of the Sun with the Earth added for scale ([[Skylab 3]], July 1973)
File:Curving prominence red.jpg|A hiding, troutlike [[Solar prominence|prominence]] is exposed when the blue [[Coronal hole|coronal]] view is combined with a red-coded ultraviolet picture that samples cooler [[Chromosphere|chromospheric]] temperatures. (Skylab 3, July 1973)
File:False Color Isophote of a Solar Eruption.jpg|[[False color]] image of a solar prominence   (Skylab 3, August 21, 1973)<ref>{{cite web |date=1973-08-21 |title=7461522 - A Solar Prominence Taken by the Skylab Telescope |url=http://mix.msfc.nasa.gov/abstracts.php?p=1375 |url-status=dead |archive-url=https://web.archive.org/web/20150428131459/https://mix.msfc.nasa.gov/abstracts.php?p=1375 |archive-date=2015-04-28 |access-date=2016-02-27 |website=Mix.msfc.nasa.gov}}</ref>
File:Solar prominence.jpg|Color processed  ultraviolet image  differentiating changes in a wispy prominence arch ([[Skylab 4]], 14 December 1973)
File:Skylab ultraviolet view of a solar prominence (7461902).jpg|Ultraviolet image of a colossal eruption (Skylab 4, December 19, 1973).
</gallery>{{clear}}

==Experiments==
The instruments were used for various types of observations including pre-planned experiments, including a set of student experiments. This is a chart describing an example of this:
[[File:Skylab X-Ray Stellar Classes graphic (0102061).jpg|thumb|left|Chart for the ED 24 experiment<ref name="msfc-students">{{cite web |last1=Floyd |first1=Henry B. |title=Skylab Student Project: Summary Description |url=https://ntrs.nasa.gov/api/citations/20160013587/downloads/20160013587.pdf |website=NASA Technical Reports Server |publisher=[[Marshall Space Flight Center]] |access-date=2022-04-16 |archive-url=https://web.archive.org/web/20220416064710/https://ntrs.nasa.gov/api/citations/20160013587/downloads/20160013587.pdf |archive-date=2022-04-16 |date=1973-03-01 |url-status=live}}</ref>]]
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==S-54 X-Ray Spectrographic Telescope==
[[File:Skylab X-ray Spectrographic Telescope (7022359).jpg|left|thumb|Skylab S-54 instrument, 1970]]
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==Legacy==
A backup ATM spare (instruments were mounted to this) was restored and put on display in 2015 at the [[Steven F. Udvar-Hazy Center]] in Chantilly, Virginia, US.<ref name="National Air and Space Museum">{{Cite news|url=https://airandspace.si.edu/stories/editorial/restoring-apollo-telescope-mount|title=Restoring the Apollo Telescope Mount|date=2015-12-10|work=National Air and Space Museum|access-date=2018-07-12|language=en}}</ref> The restoration involved repairing some [[Kapton]] layers that had degraded after 4 decades.<ref name="National Air and Space Museum"/>

==See also==
{{commons category|Apollo Telescope Mount}}
*[[Orbiting Solar Observatory]]
*[[List of X-ray space telescopes]]
*[[List of spacewalks and moonwalks 1965–1999]] (in the early 1970s several Skylab spacewalks including servicing ATM)

==References==
{{Reflist}}

==External links==
* [http://libarchstor.uah.edu:8081/repositories/2/resources/83 Apollo Telescope Mount, The University of Alabama in Huntsville Archives and Special Collections]

{{Project Skylab}}
{{Apollo program}}
{{Apollo program hardware}}
{{Space observatories}}
{{Sun spacecraft}}

{{Use American English|date=January 2014}}

[[Category:Apollo program hardware]]
[[Category:Skylab program]]
[[Category:Crewed space observatories]]
[[Category:Solar telescopes]]
[[Category:X-ray telescopes]]
[[Category:Ultraviolet telescopes]]
[[Category:Space telescopes]]
[[Category:Solar space observatories]]