Editing Hubble Space Telescope (section)

== Equipment failures ==

=== Gyroscope rotation sensors ===
HST uses gyroscopes to detect and measure any rotations so it can stabilize itself in orbit and point accurately and steadily at astronomical targets. HST has six of these rate-sensing gyroscopes installed. Three gyroscopes are normally required for operation; observations are still possible with two or one, but the area of sky that can be viewed would be somewhat restricted, and observations requiring very accurate pointing are more difficult.<ref>{{cite web |last=Sembach |first=K. R. |display-authors=etal |date=October 2004 |title=Handbook Archive – HST Two-Gyro Handbook |url=https://www.stsci.edu/hst/documentation/handbook-archive |url-status=live |archive-url=https://web.archive.org/web/20220715150328/https://www.stsci.edu/hst/documentation/handbook-archive |archive-date=July 15, 2022 |access-date=April 11, 2022 |publisher=Space Telescope Science Institute |language=en-us |location=Baltimore, Maryland |version=1.0}}</ref> In 2018, the plan was to drop into one-gyroscope mode if fewer than three working gyroscopes were operational. The gyroscopes are part of the '''Pointing Control System''', which uses five types of sensors (magnetic sensors, optical sensors, and the gyroscopes) and two types of [[actuator]]s ([[reaction wheel]]s and [[magnetic torquer]]s).<ref name=PCS>{{cite web |url=https://www.nasa.gov/content/goddard/hubble-space-telescope-pointing-control-system |title=Hubble Space Telescope Pointing Control System |date=December 19, 2017 |publisher=NASA |access-date=October 24, 2018 |archive-date=February 12, 2019 |archive-url=https://web.archive.org/web/20190212043038/https://www.nasa.gov/content/goddard/hubble-space-telescope-pointing-control-system/ |url-status=live }}</ref>

After the [[Space Shuttle Columbia disaster|''Columbia'' disaster]] in 2003, it was unclear whether another servicing mission would be possible, and gyroscope life became a concern again, so engineers developed new software for two-gyroscope and one-gyroscope modes to maximize the potential lifetime. The development was successful, and in 2005, it was decided to switch to two-gyroscope mode for regular telescope operations as a means of extending the lifetime of the mission. The switch to this mode was made in August 2005, leaving Hubble with two gyroscopes in use, two on backup, and two inoperable.<ref>{{cite web |url=https://www.nasa.gov/home/hqnews/2005/aug/HQ_05242_hst_2_gyros.html |title=Hubble Space Telescope Begins 'Two-Gyro' Science Operations |publisher=NASA |first1=Dolores |last1=Beasley |first2=Susan |last2=Hendrix |first3=Donna |last3=Weaver |date=August 31, 2005 |access-date=February 8, 2019 |archive-date=May 8, 2017 |archive-url=https://web.archive.org/web/20170508183817/https://www.nasa.gov/home/hqnews/2005/aug/HQ_05242_hst_2_gyros.html |url-status=live }}</ref> One more gyroscope failed in 2007.<ref>{{cite news |url=https://www.newscientist.com/article/dn12600-hubble-telescope-loses-another-gyroscope-.html |title=Hubble telescope loses another gyroscope |work=New Scientist |first=Jeff |last=Hecht |date=September 6, 2007 |access-date=January 6, 2009 |archive-date=January 22, 2012 |archive-url=https://web.archive.org/web/20120122235904/http://www.newscientist.com/article/dn12600-hubble-telescope-loses-another-gyroscope-.html |url-status=live }}</ref>

By the time of the final repair mission in May 2009, during which all six gyroscopes were replaced (with two new pairs and one refurbished pair), only three were still working. Engineers determined that the gyroscope failures were caused by corrosion of electric wires powering the motor that was initiated by oxygen-pressurized air used to deliver the thick suspending fluid.<ref name="Gyros">{{cite web |url=http://www.spacetelescope.org/about/general/gyroscopes/ |title=Gyroscopes |publisher=ESA |access-date=June 9, 2012 |archive-date=May 7, 2012 |archive-url=https://web.archive.org/web/20120507051926/http://www.spacetelescope.org/about/general/gyroscopes/ |url-status=live }}</ref> The new gyroscope models were assembled using pressurized nitrogen<ref name="Gyros" /> and were expected to be much more reliable.<ref>{{cite news |url=http://spaceflightnow.com/shuttle/sts125/081030hubble |title=Endeavour to go Nov. 14; Hubble slips deeper into '09 |work=Spaceflight Now |first=William |last=Harwood |date=October 30, 2008 |access-date=January 6, 2009 |archive-date=December 19, 2008 |archive-url=https://web.archive.org/web/20081219074629/http://spaceflightnow.com/shuttle/sts125/081030hubble/ |url-status=live }}</ref> In the 2009 servicing mission all six gyroscopes were replaced, and after almost ten years only three gyroscopes failed, and only after exceeding the average expected run time for the design.<ref>{{Cite web |url=https://www.nasa.gov/feature/goddard/2018/update-on-the-hubble-space-telescope-safe-mode |title=Update on the Hubble Space Telescope Safe Mode |publisher=NASA |last=Garner |first=Rob |date=October 8, 2018 |access-date=October 15, 2018 |archive-date=October 12, 2018 |archive-url=https://web.archive.org/web/20181012181705/https://www.nasa.gov/feature/goddard/2018/update-on-the-hubble-space-telescope-safe-mode/ |url-status=live }}</ref>

Of the six gyroscopes replaced in 2009, three were of the old design susceptible for flex-lead failure, and three were of the new design with a longer expected lifetime. The first of the old-style gyroscopes failed in March 2014, and the second in April 2018. On October 5, 2018, the last of the old-style gyroscopes failed, and one of the new-style gyroscopes was powered-up from standby state. However, that reserve gyroscope did not immediately perform within operational limits, and so the observatory was placed into "safe" mode while scientists attempted to fix the problem.<ref>{{cite news |url=https://www.bbc.co.uk/news/science-environment-45788412 |title=Hubble telescope hit by mechanical failure |work=BBC News |first=Paul |last=Rincon |date=October 8, 2018 |access-date=October 10, 2018 |archive-date=October 10, 2018 |archive-url=https://web.archive.org/web/20181010083018/https://www.bbc.co.uk/news/science-environment-45788412 |url-status=live }}</ref><ref>{{cite news |url=https://spacenews.com/nasa-makes-progress-on-fixing-hubble-gyro/ |title=NASA makes progress on fixing Hubble gyro |publisher=Space News |first=Jeff |last=Foust |date=October 22, 2018 |access-date=October 23, 2018 |archive-date=October 23, 2018 |archive-url=https://archive.today/20181023154456/https://spacenews.com/nasa-makes-progress-on-fixing-hubble-gyro/ |url-status=live }}</ref> NASA tweeted on October 22, 2018, that the "rotation rates produced by the backup gyro have reduced and are now within a normal range. Additional tests {{interp|are}} to be performed to ensure Hubble can return to science operations with this gyro."<ref>{{cite news |url=https://www.usatoday.com/story/news/nation-now/2018/10/24/nasa-hubble-space-telescope-fixed-turning-switch-off/1748161002/ |title=What fixed NASA's Hubble Space Telescope? Someone flipped a switch on and off |work=USA Today |first=Brett |last=Molina |date=October 24, 2018 |access-date=February 8, 2019 |archive-date=April 11, 2019 |archive-url=https://web.archive.org/web/20190411082344/https://www.usatoday.com/story/news/nation-now/2018/10/24/nasa-hubble-space-telescope-fixed-turning-switch-off/1748161002/ |url-status=live }}</ref>

The solution that restored the backup new-style gyroscope to operational range was widely reported as "turning it off and on again".<ref>{{cite news |url=https://www.washingtonpost.com/science/2018/10/24/no-nasa-didnt-fix-hubble-telescope-by-just-turning-it-off-again/ |title=No, NASA didn't fix the Hubble Telescope by just turning it off and on again |newspaper=The Washington Post |first=Amy B. |last=Wang |date=October 24, 2018 |access-date=February 8, 2019 |archive-date=December 31, 2018 |archive-url=https://web.archive.org/web/20181231194139/https://www.washingtonpost.com/science/2018/10/24/no-nasa-didnt-fix-hubble-telescope-by-just-turning-it-off-again/ |url-status=live }}</ref> A "running restart" of the gyroscope was performed, but this had no effect, and the final resolution to the failure was more complex. The failure was attributed to an inconsistency in the fluid surrounding the float within the gyroscope (e.g., an air bubble). On October 18, 2018, the Hubble Operations Team directed the spacecraft into a series of maneuvers—moving the spacecraft in opposite directions—in order to mitigate the inconsistency. Only after the maneuvers, and a subsequent set of maneuvers on October 19, did the gyroscope truly operate within its normal range.<ref>{{cite web |url=https://www.nasa.gov/feature/goddard/2018/update-on-the-hubble-space-telescope-safe-mode |title=NASA's Hubble Space Telescope Returns to Science Operations |publisher=NASA |first=Felicia |last=Chou |date=October 27, 2018 |access-date=February 8, 2019 |archive-date=February 8, 2019 |archive-url=https://web.archive.org/web/20190208102958/https://www.nasa.gov/feature/goddard/2018/update-on-the-hubble-space-telescope-safe-mode/ |url-status=live }}</ref>

=== Instruments and electronics ===
[[File:Formalhaut b.jpg|thumb|upright=1.6|Hubble views the [[Fomalhaut]] system. This false-color image was taken in October 2004 and July 2006 with the Advanced Camera for Surveys.]]

Past servicing missions have exchanged old instruments for new ones, avoiding failure and making new types of science possible. Without servicing missions, all the instruments will eventually fail. In August 2004, the power system of the Space Telescope Imaging Spectrograph (STIS) failed, rendering the instrument inoperable. The electronics had originally been fully redundant, but the first set of electronics failed in May 2001.<ref>{{cite web|url=http://www.stsci.edu/instruments/stis/|title=Space Telescope Imaging Spectrograph|publisher=STScI|access-date=April 26, 2008|archive-date=May 30, 2012|archive-url=https://archive.today/20120530063505/http://www.stsci.edu/instruments/stis/|url-status=live}}</ref> This power supply was fixed during Servicing Mission{{nbsp}}4 in May 2009.<ref>{{Cite web |last=Garner |first=Rob |date=June 2, 2012 |title=Hubble Servicing Missions {{!}} Servicing Mission 4 |url=http://www.nasa.gov/content/goddard/hubble-servicing-mission-4 |access-date=April 6, 2022 |website=NASA |archive-date=April 6, 2022 |archive-url=https://web.archive.org/web/20220406230904/https://www.nasa.gov/content/goddard/hubble-servicing-mission-4/ |url-status=live }}</ref>

Similarly, the Advanced Camera for Surveys (ACS) main camera primary electronics failed in June 2006, and the power supply for the backup electronics failed on January 27, 2007.<ref>{{cite web|url=http://www.nasa.gov/home/hqnews/2007/jan/HQ_0715_Hubble_ACS.html|title=Engineers Investigate Issue on One of Hubble's Science Instruments|date=January 29, 2007|publisher=NASA|access-date=April 26, 2008|archive-date=May 14, 2007|archive-url=https://web.archive.org/web/20070514132230/http://www.nasa.gov/home/hqnews/2007/jan/HQ_0715_Hubble_ACS.html|url-status=live}}</ref> Only the instrument's Solar Blind Channel (SBC) was operable using the side-1 electronics. A new power supply for the wide angle channel was added during SM 4, but quick tests revealed this did not help the high resolution channel.<ref>{{cite web|url=http://www.stsci.edu/hst/acs|title=Advanced Camera for Surveys|publisher=STScI|access-date=May 21, 2009|archive-date=August 5, 2012|archive-url=https://archive.today/20120805175005/http://www.stsci.edu/hst/acs|url-status=live}}</ref> The Wide Field Channel (WFC) was returned to service by STS-125 in May 2009 but the High Resolution Channel (HRC) remains offline.<ref>{{cite news|url=http://spaceflightnow.com/shuttle/sts125/090517fd7/index.html|title=Part of camera in newly repaired instrument revived|last=Harwood|first=William|date=May 17, 2009|work=Spaceflight Now|access-date=May 17, 2009|archive-url=https://web.archive.org/web/20090520152548/http://www.spaceflightnow.com/shuttle/sts125/090517fd7/index.html|archive-date=May 20, 2009}}</ref>

On January 8, 2019, Hubble entered a partial safe mode following suspected hardware problems in its most advanced instrument, the Wide Field Camera 3 instrument. NASA later reported that the cause of the safe mode within the instrument was a detection of voltage levels out of a defined range. On January 15, 2019, NASA said the cause of the failure was a software problem. Engineering data within the telemetry circuits were not accurate. In addition, all other telemetry within those circuits also contained erroneous values indicating that this was a telemetry issue and not a power supply issue. After resetting the telemetry circuits and associated boards the instrument began functioning again. On January 17, 2019, the device was returned to normal operation and on the same day it completed its first science observations.<ref>{{cite web|url=https://www.nasa.gov/feature/goddard/2019/wide-field-camera-3-anomaly-on-hubble-space-telescope|title=Hubble's Wide Field Camera{{nbsp}}3 Recovered, Collecting Science Data|last=Gutro|first=Rob|date=January 17, 2019|publisher=NASA|access-date=January 13, 2019|archive-date=January 11, 2019|archive-url=https://web.archive.org/web/20190111201925/https://www.nasa.gov/feature/goddard/2019/wide-field-camera-3-anomaly-on-hubble-space-telescope|url-status=live}}</ref><ref>{{cite news|url=https://www.spaceflightinsider.com/missions/space-observatories/hubbles-wide-field-camera-3-resumes-operations/|title=Hubble's Wide Field Camera{{nbsp}}3 resumes operations|last=Kornfeld|first=Laurel|date=January 17, 2019|work=Spaceflight Insider|access-date=February 9, 2019|archive-date=February 9, 2019|archive-url=https://web.archive.org/web/20190209180224/https://www.spaceflightinsider.com/missions/space-observatories/hubbles-wide-field-camera-3-resumes-operations/|url-status=live}}</ref>

==== 2021 power control issue ====
On June 13, 2021, Hubble's payload computer halted due to a suspected issue with a memory module. An attempt to restart the computer on June 14 failed. Further attempts to switch to one of three other backup memory modules on board the spacecraft failed on June 18. On June 23 and 24, NASA engineers switched Hubble to a backup payload computer, but these operations have failed as well with the same error. On June 28, 2021, NASA announced that it was extending the investigation to other components.<ref>{{Cite web|date=June 26, 2021|title=NASA Continues Work on Hubble Space Telescope – Backup Computer Turned On, but It Fails With the Same Error|url=https://scitechdaily.com/nasa-continues-work-on-hubble-space-telescope-backup-computer-turned-on-but-it-fails-with-the-same-error/|access-date=June 26, 2021|website=SciTechDaily|archive-date=June 26, 2021|archive-url=https://web.archive.org/web/20210626142712/https://scitechdaily.com/nasa-continues-work-on-hubble-space-telescope-backup-computer-turned-on-but-it-fails-with-the-same-error/|url-status=live}}</ref><ref>{{Cite web |last=Mathewson |first=Samantha |date=2021-06-28 |title=No quick fix for Hubble Space Telescope's computer glitch, NASA says |url=https://www.space.com/nasa-investigates-hubble-space-telescope-computer-glitch |access-date=2023-10-15 |website=Space.com |language=en-us |archive-date=July 15, 2022 |archive-url=https://web.archive.org/web/20220715150344/https://www.space.com/nasa-investigates-hubble-space-telescope-computer-glitch |url-status=live }}</ref> Scientific operations were suspended while NASA worked to diagnose and resolve the issue.<ref name="AP: Computer trouble, science halted">{{Cite web |last=Dunn |first=Marcia |date=June 16, 2021 |title=Computer trouble hits Hubble Space Telescope, science halted |url=https://apnews.com/article/business-science-d0042c12554759cf2d00668d5dcd031b |access-date=June 20, 2021 |website=[[Associated Press|AP NEWS]] |archive-date=June 16, 2021 |archive-url=https://web.archive.org/web/20210616205037/https://apnews.com/article/business-science-d0042c12554759cf2d00668d5dcd031b |url-status=live }}</ref><ref>{{Cite web |last=Jenner |first=Lynn |date=June 16, 2021 |title=Operations Underway to Restore Payload Computer on NASA's Hubble |url=http://www.nasa.gov/feature/goddard/2021/operations-underway-to-restore-payload-computer-on-nasas-hubble-space-telescope |access-date=June 20, 2021 |website=NASA |archive-date=June 20, 2021 |archive-url=https://web.archive.org/web/20210620010610/http://www.nasa.gov/feature/goddard/2021/operations-underway-to-restore-payload-computer-on-nasas-hubble-space-telescope/ |url-status=live }}</ref> After identifying a malfunctioning power control unit (PCU) supplying power to one of Hubble's computers, NASA was able to switch to a backup PCU and bring Hubble back to operational mode on July 16.<ref>{{Cite web |date=2021-07-19 |title=NASA Returns Hubble Space Telescope to Science Operations – NASA |url=https://www.nasa.gov/solar-system/nasa-returns-hubble-space-telescope-to-science-operations/ |access-date=2023-10-15 |language=en-US |archive-date=October 23, 2023 |archive-url=https://web.archive.org/web/20231023194702/https://www.nasa.gov/solar-system/nasa-returns-hubble-space-telescope-to-science-operations/ |url-status=live }}</ref><ref>{{Cite web|title=Hobbled Hubble Telescope Springs Back To Life On Its Backup System|url=https://www.npr.org/2021/07/16/1016953132/hobbled-hubble-telescope-springs-back-to-life-on-its-backup-system|access-date=July 16, 2021|website=NPR|date=July 16, 2021 |archive-date=July 16, 2021|archive-url=https://web.archive.org/web/20210716201637/https://www.npr.org/2021/07/16/1016953132/hobbled-hubble-telescope-springs-back-to-life-on-its-backup-system|url-status=live|last1=Chappell |first1=Bill }}</ref><ref>{{cite news|last=Clery|first=Daniel|date=July 16, 2021|title='Hubble is back!' Famed space telescope has new lease on life after computer swap appears to fix glitch|url=https://www.science.org/content/article/hubble-back-famed-space-telescope-has-new-lease-life-after-computer-swap-appears-fix|work=[[Science (magazine)|Science]]|location=|access-date=July 16, 2021|archive-date=October 21, 2021|archive-url=https://web.archive.org/web/20211021183821/https://www.science.org/content/article/hubble-back-famed-space-telescope-has-new-lease-life-after-computer-swap-appears-fix|url-status=live}}</ref><ref>{{cite news|last=Hunt|first=Katie|date=July 19, 2021|title=The Hubble Space Telescope is functioning again after more than month offline|url=https://www.cnn.com/2021/07/19/world/hubble-telescope-nasa-scn/index.html|work=[[CNN]]|location=|access-date=July 19, 2021|archive-date=July 19, 2021|archive-url=https://web.archive.org/web/20210719131659/https://www.cnn.com/2021/07/19/world/hubble-telescope-nasa-scn/index.html|url-status=live}}</ref> On October 23, 2021, HST instruments reported missing synchronization messages<ref>{{cite web |url=https://hubblesite.org/contents/news-releases/2021/news-2021-064 |title=Hubble Instruments Remain in Safe Mode, NASA Team Investigating |website=HubbleSite.org |publisher=[[Space Telescope Science Institute]] |date=November 4, 2021 |access-date=November 24, 2021 |archive-date=November 24, 2021 |archive-url=https://web.archive.org/web/20211124151859/https://hubblesite.org/contents/news-releases/2021/news-2021-064 |url-status=live }}</ref> and went into safe mode.<ref>{{cite web|url=https://www.space.com/hubble-space-telescope-wide-field-camera-3-recovered|title=Hubble Space Telescope team revives powerful camera instrument after glitch|website=[[Space.com]]|date=November 22, 2021|access-date=November 24, 2021|archive-date=November 23, 2021|archive-url=https://web.archive.org/web/20211123205854/https://www.space.com/hubble-space-telescope-wide-field-camera-3-recovered|url-status=live}}</ref> By December 8, 2021, NASA had restored full science operations and was developing updates to make instruments more resilient to missing synchronization messages.<ref>{{Cite web |last=Adkins |first=Jamie |date=December 8, 2021 |title=NASA Returns Hubble to Full Science Operations |url=https://www.nasa.gov/feature/goddard/2021/nasa-returns-hubble-to-full-science-operations |access-date=December 8, 2021 |website=NASA |archive-date=December 7, 2021 |archive-url=https://web.archive.org/web/20211207235922/http://www.nasa.gov/feature/goddard/2021/nasa-returns-hubble-to-full-science-operations/ |url-status=live }}</ref>