Editing Hubble Space Telescope (section)

== {{anchor|Servicing}} Servicing missions and new instruments ==
=== Servicing overview ===
<!-- Subheading above added to ease editing of the timeline defined below. -->
<div style="float: right; clear: right; margin: 0 0 1em 1em; padding: 3px;">
<timeline>
# see [[Help:EasyTimeline syntax]]
# consider converting this to a template 
ImageSize = width:420 height:200    # increase height to allow for title text/legend
PlotArea  = width:400 height:140 left:10 bottom:20   # width & height should no longer be used - chg to  top:40 right:10 
AlignBars = justify # no space above or below

TextData =  # legend might be better
  fontsize:M
  pos:(50,190)  # top, above bars
  text:Instruments installed in the radial bay and 4 axial bays
  
Colors =
  id:lightGray     value:gray(0.999999)
  id:darkGray      value:gray(0.2)
  id:ren      value:rgb(0.6,1,1)   # cyan
  id:bar      value:rgb(0.6,1,0.6) # apple greem
  id:cla      value:rgb(1,1,0.6)   # custard yellow
 id:lightred2 value:rgb(1,0.9,0.9) # pink

BackgroundColors= canvas:lightGray

Period     = from:1990 till:2022
TimeAxis   = orientation:horizontal
ScaleMajor = unit:year increment:5 start:1990 gridcolor:darkgray
ScaleMinor = unit:year increment:1 start:1990
# default DateFormat = x.y  (year.decimal?)
# SM1 was Dec 1993 (1993.9), SM2...  SM4 was May 2009 (2009.4)

# So timeline autoextends, Consider using 
# Period     = from:1990 till:{{#expr:{{#time:Y}}+{{#time:m}}/12}}

PlotData=
  align:left  anchor:from  shift:(10,-4)  # bar label text, start at left end, centred vertically

  bar:&nbsp;

   from:1990 till:1993.9 color:Ren text:[[Wide Field and Planetary Camera|WFPC]]
   from:1993.9 till:2009.4 color:Bar text:[[Wide Field and Planetary Camera 2|WFPC2]]
   from:2009.4 till:end color:Cla text:[[Wide Field Camera 3|WFC3]]

  bar:&nbsp;&nbsp;

   from:1990 till:1997 color:Ren text:[[Goddard High Resolution Spectrograph|GHRS]]
   from:1997 till:2008 color:Bar text:[[Near Infrared Camera and Multi-Object Spectrometer|NICMOS]]
   from:2008 till:end color:lightred2 text:NICMOS Offline

  bar:&nbsp;&nbsp;&nbsp;

   from:1990 till:1993.9 color:Ren text:[[High Speed Photometer|HSP]]
   from:1993.9 till:2009.4 color:Bar text:[[Corrective Optics Space Telescope Axial Replacement|COSTAR]]
   from:2009.4 till:end color:Cla text:[[Cosmic Origins Spectrograph|COS]]

  bar:&nbsp;&nbsp;&nbsp;&nbsp;

   from:1990 till:2002 color:Ren text:[[Faint Object Camera|FOC]]
   from:2002 till:end color:Bar text:[[Advanced Camera for Surveys|ACS]]

  bar:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

   from:1990 till:1997 color:Ren text:[[Faint Object Spectrograph|FOS]]
   from:1997 till:2004.7 color:Bar text:[[Space Telescope Imaging Spectrograph|STIS]]
   from:2004.7 till:2009.4 color:lightred2 text:failed
   from:2009.4 till:end color:Bar text:[[Space Telescope Imaging Spectrograph|STIS]]

</timeline>
</div>

Hubble was designed to accommodate regular servicing and equipment upgrades while in orbit. Instruments and limited life items were designed as [[orbital replacement unit (HST)|orbital replacement units]].<ref>{{Cite web |date=2013-02-19 |title=Hubble Space Telescope (HST) Archive System |url=http://setas-www.larc.nasa.gov/HUBBLE/HARDWARE/hubble_ORU.html |access-date=2024-01-31 |archive-url=https://web.archive.org/web/20130219022932/http://setas-www.larc.nasa.gov/HUBBLE/HARDWARE/hubble_ORU.html |archive-date=February 19, 2013 }}</ref> Five servicing missions (SM 1, 2, 3A, 3B, and 4) were flown by NASA [[Space Shuttle]]s, the first in December 1993 and the last in May 2009.<ref name="hubble-timeline">{{cite web |url=https://www.nationalgeographic.com/hubble-timeline/ |title=The Secret to Hubble's Success |work=National Geographic |first1=Jason |last1=Treat |first2=Anna |last2=Scalamogna |first3=Eve |last3=Conant |date=2015 |access-date=April 25, 2015 |archive-date=April 28, 2015 |archive-url=https://web.archive.org/web/20150428040059/http://www.nationalgeographic.com/hubble-timeline/ |url-status=live }}</ref> Servicing missions were delicate operations that began with maneuvering to intercept the telescope in orbit and carefully retrieving it with the shuttle's [[Canadarm|mechanical arm]]. The necessary work was then carried out in multiple tethered [[spacewalk]]s over a period of four to five days. After a visual inspection of the telescope, astronauts conducted repairs, replaced failed or degraded components, upgraded equipment, and installed new instruments. Once work was completed, the telescope was redeployed, typically after boosting to a higher orbit to address the [[orbital decay]] caused by atmospheric [[drag (physics)|drag]].<ref name="nytimes20150424">{{cite web |url=https://www.nytimes.com/video/science/100000003647066/hubble-reflects-the-cosmos.html |title=Hubble Reflects the Cosmos |work=The New York Times |first1=Jason |last1=Overbye |first2=Jonathan |last2=Corum |first3=Jason |last3=Drakeford |date=April 24, 2015 |access-date=April 25, 2015 |archive-date=February 2, 2019 |archive-url=https://web.archive.org/web/20190202112051/https://www.nytimes.com/video/science/100000003647066/hubble-reflects-the-cosmos.html |url-status=live }}</ref>

=== Servicing Mission 1 ===
{{Main|STS-61}}
[[File:Upgrading Hubble during SM1.jpg|thumb|right|Astronauts Musgrave and Hoffman install corrective optics during SM1]]

The first Hubble servicing mission was scheduled for 1993 before the mirror problem was discovered. It assumed greater importance, as the astronauts would need to do extensive work to install corrective optics; failure would have resulted in either abandoning Hubble or accepting its permanent disability. Other components failed before the mission, causing the repair cost to rise to $500&nbsp;million (not including the cost of the shuttle flight). A successful repair would help demonstrate the viability of building [[Space Station Alpha]].{{sfn|Tatarewicz|1998|pp=374,378,381,388}}

[[STS-49]] in 1992 demonstrated the difficulty of space work. While its rescue of [[Intelsat 603]] received praise, the astronauts had taken possibly reckless risks in doing so. Neither the rescue nor the unrelated assembly of prototype space station components occurred as the astronauts had trained, causing NASA to reassess planning and training, including for the Hubble repair. The agency assigned to the mission [[Story Musgrave]]—who had worked on satellite repair procedures since 1976—and six other experienced astronauts, including two from STS-49. The first mission director since [[Project Apollo]]{{clarify|date=August 2023}} would coordinate a crew with 16 previous shuttle flights. The astronauts were trained to use about a hundred specialized tools.{{sfn|Tatarewicz|1998|pp=380-381,384–387}}

Heat had been the problem on prior spacewalks, which occurred in sunlight. Hubble needed to be repaired out of sunlight. Musgrave discovered during vacuum training, seven months before the mission, that spacesuit gloves did not sufficiently protect against the cold of space. After [[STS-57]] confirmed the issue in orbit, NASA quickly changed equipment, procedures, and flight plan. Seven total mission simulations occurred before launch, the most thorough preparation in shuttle history. No complete Hubble mockup existed, so the astronauts studied many separate models (including one at the Smithsonian) and mentally combined their varying and contradictory details.{{sfn|Tatarewicz|1998|pp=384–387}}

Service Mission 1 flew aboard [[Space Shuttle Endeavour|''Endeavour'']] in December 1993, and involved installation of several instruments and other equipment over ten days. Most importantly, the [[High Speed Photometer]] was replaced with the [[Corrective Optics Space Telescope Axial Replacement|COSTAR]] corrective optics package, and WF/PC was replaced with the [[Wide Field and Planetary Camera 2]] (WFPC2) with an internal optical correction system. The [[Photovoltaic module|solar arrays]] and their drive electronics were also replaced, as well as four gyroscopes in the telescope pointing system, two electrical control units and other electrical components, and two magnetometers. The onboard computers were upgraded with added [[coprocessor]]s, and Hubble's orbit was boosted.<ref name="Servicing Mission 1" />

On January 13, 1994, NASA declared the mission a complete success and showed the first sharper images.<ref>{{cite journal |title=The on-orbit performance of WFPC2 |journal=Astrophysical Journal Letters |first1=J. T. |last1=Trauger |first2=G. E. |last2=Ballester |first3=C. J. |last3=Burrows |first4=S. |last4=Casertano |first5=J. T. |last5=Clarke |first6=D. |last6=Crisp |first7=R. W. |last7=Evans |first8=J. S. |last8=Gallagher III |first9=R. E. |last9=Griffiths |display-authors=4 |volume=435 |pages=L3–L6 |date=1994 |bibcode=1994ApJ...435L...3T |doi=10.1086/187580 |url=https://authors.library.caltech.edu/53641/ |access-date=January 7, 2022 |archive-date=January 7, 2022 |archive-url=https://web.archive.org/web/20220107163225/https://authors.library.caltech.edu/53641/ |url-status=live }}</ref> The mission was one of the most complex performed to that date, involving five long [[extra-vehicular activity]] periods. Its success was a boon for NASA, as well as for the astronomers who now had a more capable space telescope.<ref name=":2" /><ref>{{Cite web |last=DeVorkin |first=David |date=April 24, 2020 |title=Telling Hubble's Story for 30 Years |url=https://airandspace.si.edu/stories/editorial/telling-hubbles-story-30-years |access-date=April 7, 2022 |website=National Air and Space Museum |publisher=Smithsonian Institution |language=en |archive-date=December 31, 2021 |archive-url=https://web.archive.org/web/20211231011831/https://airandspace.si.edu/stories/editorial/telling-hubbles-story-30-years |url-status=live }}</ref>

=== Servicing Mission 2 ===
{{Main|STS-82}}
[[File:Hubble Space Telescope (27946391011).jpg|thumb|Hubble as seen from ''Discovery'' during its second servicing mission]]

Servicing Mission 2, flown by ''Discovery'' in February 1997, replaced the GHRS and the FOS with the [[Space Telescope Imaging Spectrograph]] (STIS) and the [[Near Infrared Camera and Multi-Object Spectrometer]] (NICMOS), replaced an Engineering and Science Tape Recorder with a new Solid State Recorder, and repaired thermal insulation.<ref>{{cite web |url=http://hubble.nasa.gov/missions/sm2.php |title=Servicing Mission 2 |publisher=NASA |access-date=April 26, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080419153631/http://hubble.nasa.gov/missions/sm2.php <!--Added by H3llBot--> |archive-date=April 19, 2008}}</ref> NICMOS contained a [[heat sink]] of solid [[nitrogen]] to reduce the [[thermal noise]] from the instrument, but shortly after it was installed, an unexpected [[thermal expansion]] resulted in part of the heat sink coming into contact with an optical baffle. This led to an increased warming rate for the instrument and reduced its original expected lifetime of 4.5 years to about two years.<ref name="NICMOStemp">{{cite web |url=http://www.stsci.edu/hst/nicmos/performance/temperature |title=NICMOS Thermal History |publisher=STScI |access-date=April 26, 2008 |archive-date=May 24, 2012 |archive-url=https://archive.today/20120524183957/http://www.stsci.edu/hst/nicmos/performance/temperature |url-status=live }}</ref><!--This reference only generally supports these two sentences, and does not give numbers such as the expected lifetime figures stated here.-->

=== Servicing Mission 3A ===
{{Main|STS-103}}

Servicing Mission 3A, flown by ''Discovery'', took place in December 1999, and was a split-off from Servicing Mission{{nbsp}}3 after three of the six onboard gyroscopes had failed. The fourth failed a few weeks before the mission, rendering the telescope incapable of performing scientific observations. The mission replaced all six [[gyroscope]]s, replaced a Fine Guidance Sensor and the computer, installed a Voltage/temperature Improvement Kit (VIK) to prevent battery overcharging, and replaced thermal insulation blankets.<ref>{{cite web |url=http://sm3a.gsfc.nasa.gov/overview.html |title=Servicing Mission 3A Overview |publisher=NASA |access-date=April 26, 2008 |archive-date=May 9, 2008 |archive-url=https://web.archive.org/web/20080509190700/http://sm3a.gsfc.nasa.gov/overview.html |url-status=live }}</ref>

=== Servicing Mission 3B ===
{{Main|STS-109}}

Servicing Mission 3B flown by ''Columbia'' in March 2002 saw the installation of a new instrument, with the FOC (which, except for the Fine Guidance Sensors when used for astrometry, was the last of the original instruments) being replaced by the [[Advanced Camera for Surveys]] (ACS). This meant COSTAR was no longer required, since all new instruments had built-in correction for the main mirror aberration.<ref name="COSTARNotNeeded">{{cite web |at=Corrective Optics Space Telescope Axial Replacement |title=HST |url=http://www.stsci.edu/hst/HST_overview/index_html#costar |publisher=STScI |access-date=November 4, 2012 |archive-date=July 15, 2022 |archive-url=https://web.archive.org/web/20220715150044/https://www.stsci.edu/hst#costar |url-status=live }}</ref> The mission also revived NICMOS by installing a closed-cycle cooler<ref name="NICMOStemp" /> and replaced the solar arrays for the second time, providing 30 percent more power.<ref>{{cite web |url=http://hubble.nasa.gov/missions/sm3b.php |title=Servicing Mission 3 |publisher=NASA |access-date=April 26, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080407164008/http://hubble.nasa.gov/missions/sm3b.php<!--Added by H3llBot--> |archive-date=April 7, 2008}}</ref>
{{clear}}

=== Servicing Mission 4 ===
{{Main|STS-125}}
{{multiple image
| align             = left
| direction         = vertical
| width             = 220
| image1            = STS-125 May 17 EVA.jpg
| caption1          = Hubble during Servicing Mission 4
| image2            = Hubble telescope 2009.jpg
| caption2          = Hubble after release
}}

Plans called for Hubble to be serviced in February 2005, but the [[Columbia disaster|''Columbia'' disaster]] in 2003, in which the orbiter disintegrated on re-entry into the atmosphere, had wide-ranging effects to the Hubble program and other NASA missions. NASA Administrator [[Sean O'Keefe]] decided all future shuttle missions had to be able to reach the safe haven of the [[International Space Station]] should in-flight problems develop. As no shuttles were capable of reaching both HST and the space station during the same mission, future crewed service missions were canceled.<ref>{{cite web |url=http://www.stsci.edu/resources/sm4meeting.html |archive-url=https://web.archive.org/web/20080511180517/http://www.stsci.edu/resources/sm4meeting.html |url-status=dead |archive-date=May 11, 2008 |title=Servicing Mission 4 Cancelled |publisher=STScI |date=January 16, 2004 |access-date=April 28, 2008 }}</ref> This decision was criticized by numerous astronomers who felt Hubble was valuable enough to merit the human risk.<ref name=NAS2005>{{cite book |url=http://www.nap.edu/catalog.php?record_id=11169 |title=Assessment of Options for Extending the Life of the Hubble Space Telescope: Final Report |publisher=The National Academies |date=2005 |doi=10.17226/11169 |isbn=978-0-309-09530-3 |access-date=December 9, 2012 |archive-date=July 15, 2022 |archive-url=https://web.archive.org/web/20220715150046/https://nap.nationalacademies.org/catalog/11169/assessment-of-options-for-extending-the-life-of-the-hubble-space-telescope |url-status=live }} Chapter 7, "Given the intrinsic value of a serviced Hubble, and the high likelihood of success for a shuttle servicing mission, the committee judges that such a mission is worth the risk."</ref> HST's planned successor, the James Webb Space Telescope (JWST), by 2004 was not expected to launch until at least 2011. JWST was eventually launched in December 2021.<ref name="AS-20211225">{{cite press release |url=https://www.arianespace.com/press-release/ariane-5-successful-launch-webb-space-telescope/ |title=Ariane 5 goes down in history with successful launch of Webb |work=[[Arianespace]] |date=December 25, 2021 |access-date=December 25, 2021 |archive-url=https://web.archive.org/web/20220310095539/https://www.arianespace.com/press-release/ariane-5-successful-launch-webb-space-telescope/ |archive-date=March 10, 2022 |url-status=live }}</ref> A gap in space-observing capabilities between a decommissioning of Hubble and the commissioning of a successor was of major concern to many astronomers, given the significant scientific impact of HST.<ref>{{cite web |url=https://www.nsf.gov/mps/ast/aaac/reports/annual/aaac_2004_report.pdf |title=2004 Annual Report |publisher=Astronomy and Astrophysics Advisory Committee |at=Section 3.1{{snd}}The Scientific Impact of the HST SM4 Cancellation |date=March 15, 2004 |access-date=November 5, 2012 |archive-date=March 27, 2019 |archive-url=https://web.archive.org/web/20190327090117/https://www.nsf.gov/mps/ast/aaac/reports/annual/aaac_2004_report.pdf |url-status=live }}</ref> The consideration that JWST will not be located in low Earth orbit, and therefore cannot be easily upgraded or repaired in the event of an early failure, only made concerns more acute. On the other hand, NASA officials were concerned that continuing to service Hubble would consume funds from other programs and delay the JWST.<ref>{{Cite journal |last=Guinnessy |first=Paul |date=September 2003 |title=Astronomers Lobby for New Lease on Hubble's Life |url=http://physicstoday.scitation.org/doi/10.1063/1.1620825 |journal=Physics Today |language=en |volume=56 |issue=9 |pages=29–31 |doi=10.1063/1.1620825 |bibcode=2003PhT....56i..29G |access-date=April 6, 2022 |archive-date=July 15, 2022 |archive-url=https://web.archive.org/web/20220715150045/https://physicstoday.scitation.org/doi/10.1063/1.1620825 |url-status=live }}</ref>

In January 2004, O'Keefe said he would review his decision to cancel the final servicing mission to HST, due to public outcry and requests from Congress for NASA to look for a way to save it. The National Academy of Sciences convened an official panel, which recommended in July 2004 that the HST should be preserved despite the apparent risks. Their report urged "NASA should take no actions that would preclude a space shuttle servicing mission to the Hubble Space Telescope".<ref name="Leary">{{cite news |author=Leary |first=Warren E. |date=July 14, 2004 |title=Panel Urges NASA to Save Hubble Space Telescope |url=https://www.nytimes.com/2004/07/14/us/panel-urges-nasa-to-save-hubble-space-telescope.html |url-status=live |archive-url=https://web.archive.org/web/20180216104758/http://www.nytimes.com/2004/07/14/us/panel-urges-nasa-to-save-hubble-space-telescope.html |archive-date=February 16, 2018 |access-date=November 8, 2012 |work=The New York Times }}</ref> In August 2004, O'Keefe asked Goddard Space Flight Center to prepare a detailed proposal for a robotic service mission. These plans were later canceled, the robotic mission being described as "not feasible".<ref>{{cite news |last=Gugliotta |first=Guy |date=April 12, 2005 |title=Nominee Backs a Review of NASA's Hubble Decision |url=https://www.washingtonpost.com/wp-dyn/content/article/2005/04/12/AR2005041201646.html |url-status=live |archive-url=https://web.archive.org/web/20170706134527/http://www.washingtonpost.com/wp-dyn/content/article/2005/04/12/AR2005041201646.html |archive-date=July 6, 2017 |access-date=January 10, 2007 |newspaper=The Washington Post }}</ref> In late 2004, several Congressional members, led by Senator [[Barbara Mikulski]], held public hearings and carried on a fight with much public support (including thousands of letters from school children across the U.S.) to get the Bush Administration and NASA to reconsider the decision to drop plans for a Hubble rescue mission.<ref>{{cite press release |url=http://mikulski.senate.gov/record.cfm?id=231696 |title=Mikulski Vows To Fight For Hubble |date=February 7, 2005 |publisher=[[Barbara Mikulski]] |access-date=April 26, 2008 |archive-url=https://web.archive.org/web/20080430100658/http://mikulski.senate.gov/record.cfm?id=231696 |archive-date=April 30, 2008}}</ref>

[[File:218582main Batt FS img1 lg.jpg|thumb|Nickel–hydrogen battery pack for Hubble]]
The nomination in April 2005 of a new NASA Administrator, [[Michael D. Griffin]], changed the situation, as Griffin stated he would consider a crewed servicing mission.<ref name="Green Light">{{cite news |url=http://www.nbcnews.com/id/15489217 |title=NASA gives green light to Hubble rescue |first=Alan |last=Boyle |publisher=NBC News |date=October 31, 2006 |access-date=January 10, 2007 |archive-date=November 4, 2013 |archive-url=https://web.archive.org/web/20131104010540/http://www.nbcnews.com/id/15489217/ |url-status=dead }}</ref> Soon after his appointment Griffin authorized Goddard to proceed with preparations for a crewed Hubble maintenance flight, saying he would make the final decision after the next two shuttle missions. In October 2006 Griffin gave the final go-ahead, and the 11-day mission by ''Atlantis'' was scheduled for October 2008. Hubble's main data-handling unit failed in September 2008,<ref name="suddenly quiet">{{cite web |url=http://www.sciencenews.org/view/generic/id/37004/description/Hubble_suddenly_quiet |title=Hubble suddenly quiet |last=Cowen |first=Ron |publisher=ScienceNews |date=September 29, 2008 |access-date=November 8, 2012}}</ref> halting all reporting of scientific data until its back-up was brought online on October 25, 2008.<ref>{{cite web |url=https://www.newscientist.com/article/dn15056-hubble-reopens-an-eye.html |title=Hubble re-opens an eye |last=Courtland |first=Rachel |work=New Scientist |date=October 28, 2008 |access-date=October 29, 2008 |archive-url=https://web.archive.org/web/20081029124801/http://space.newscientist.com/article/dn15056-hubble-reopens-an-eye.html |archive-date=October 29, 2008}}</ref> Since a failure of the backup unit would leave the HST helpless, the service mission was postponed to incorporate a replacement for the primary unit.<ref name="suddenly quiet" />

Servicing Mission 4 (SM4), flown by ''Atlantis'' in May 2009, was the last scheduled shuttle mission for HST.<ref name="SM4" /><ref name="May09">{{cite web |url=http://www.nasa.gov/home/hqnews/2008/dec/HQ_08-320_Hubble_May2009.html |title=NASA Sets Target Shuttle Launch Date for Hubble Servicing Mission |publisher=NASA |date=December 4, 2008 |access-date=December 5, 2008 |archive-date=December 6, 2008 |archive-url=https://web.archive.org/web/20081206005041/http://www.nasa.gov/home/hqnews/2008/dec/HQ_08-320_Hubble_May2009.html |url-status=live }}</ref> SM4 installed the replacement data-handling unit, repaired the ACS and STIS systems, installed improved [[nickel–hydrogen battery|nickel hydrogen batteries]], and replaced other components including all six gyroscopes. SM4 also installed two new observation instruments—Wide Field Camera 3 (WFC3) and the [[Cosmic Origins Spectrograph]] (COS)<ref name=HST_Opens>{{cite web |url=http://www.nasa.gov/mission_pages/hubble/science/ero_images.html |title=Hubble Opens New Eyes on the Universe |publisher=NASA |date=September 9, 2009 |access-date=May 28, 2012 |archive-date=May 27, 2012 |archive-url=https://web.archive.org/web/20120527231309/http://www.nasa.gov/mission_pages/hubble/science/ero_images.html |url-status=live }}</ref>—and the [[Soft Capture and Rendezvous System]], which will enable the future rendezvous, capture, and safe disposal of Hubble by either a crewed or robotic mission.<ref name="Soft Capture">{{cite web |url=http://www.nasa.gov/mission_pages/hubble/servicing/SM4/main/SCRS_FS_HTML.html |title=The Soft Capture and Rendezvous System |publisher=NASA |access-date=May 20, 2009 |archive-date=September 11, 2008 |archive-url=https://web.archive.org/web/20080911224222/http://www.nasa.gov/mission_pages/hubble/servicing/SM4/main/SCRS_FS_HTML.html |url-status=live }}</ref> Except for the ACS's [[Advanced Camera for Surveys#High-Resolution Channel (HRC)|High Resolution Channel]], which could not be repaired and was disabled,<ref>{{cite news |url=https://www.nytimes.com/2009/09/10/science/space/10hubble.html |title=After Hubble Repair, New Images From Space |work=The New York Times |first=Dennis |last=Overbye |date=September 9, 2009 |access-date=August 1, 2015 |archive-date=November 21, 2015 |archive-url=https://web.archive.org/web/20151121090246/http://www.nytimes.com/2009/09/10/science/space/10hubble.html |url-status=live }}</ref><ref>{{cite news |url=https://www.nytimes.com/2009/05/18/science/space/18hubble.html |title=After a Yank, 'Surgery' on Hubble Optics |work=The New York Times |first=Dennis |last=Overbye |date=May 17, 2009 |access-date=August 1, 2015 |archive-date=October 4, 2013 |archive-url=https://web.archive.org/web/20131004060543/http://www.nytimes.com/2009/05/18/science/space/18hubble.html |url-status=live }}</ref><ref>{{cite web |url=https://www.spacetelescope.org/about/history/acs_repair/ |title=Repair of the Advanced Camera for Surveys |work=SpaceTelescope.org |access-date=August 1, 2015}}</ref> the work accomplished during SM4 rendered the telescope fully functional.<ref name="SM4" />