Editing STS-31 (section)

== Mission highlights ==
[[File:STS-31 Launch - GPN-2000-000684.jpg|thumb|upright=1.3|Space Shuttle ''Discovery'' launches from LC-39B for STS-31 with ''Columbia'' on LC-39A in preparation for [[STS-35]].]]
[[File:1990 s31 IMAX view of HST in payload bay.jpg|upright=1.3|thumb|Hubble Space Telescope in the cargo bay of ''Discovery'']]

STS-31 was launched on April 24, 1990, at 12:33:51{{nbsp}}[[Coordinated Universal Time|UTC]] (8:33:51{{nbsp}}am{{nbsp}}[[Eastern Daylight Time|EDT]], local time at the launch site). A launch attempt on April 10, 1990, was scrubbed at T''−''4 minutes for a faulty valve in [[auxiliary power unit]] (APU) number one. The APU was eventually replaced, and the Hubble Space Telescope's batteries were recharged. On launch day, the countdown was briefly halted at T''−''31 seconds when ''Discovery''{{'}}s computers failed to shut down a fuel valve line on ground support equipment. Engineers manually commanded the valve to close and the countdown continued.<ref name="MSER STS-31">{{cite web|publisher=NASA Office of Safety, Reliability, Maintainability and Quality Assurance|title=Misson Safety Evaluation Report for STS-31 – Postflight Edition|url=https://ntrs.nasa.gov/api/citations/19920012273/downloads/19920012273.pdf|archive-url=https://web.archive.org/web/20210107105312/https://ntrs.nasa.gov/api/citations/19920012273/downloads/19920012273.pdf|archive-date=January 7, 2021|location=Washington, D.C.|page=7-1|date=October 15, 1990|url-status=live}} {{PD-notice}}</ref>

The main purpose of this mission was to deploy Hubble. It was designed to operate above the Earth's turbulent and obscuring atmosphere to observe celestial objects at [[ultraviolet]], [[Visible spectrum|visible]] and [[Infrared|near-infrared]] [[wavelength]]s. The Hubble mission was a joint NASA-ESA ([[European Space Agency]]) effort going back to the late 1970s.<ref name="NewScientist 1990-07-07">{{cite news |last1=Gavaghan|first1=Helen|title=Design flaw cripples Hubble telescope|url=https://www.newscientist.com/article/mg12717240-300-design-flaw-cripples-hubble-telescope/|url-status=live|publisher=New Scientist |issue=1724|date=July 7, 1990|archive-url=https://web.archive.org/web/20210107115137/https://www.newscientist.com/article/mg12717240-300-design-flaw-cripples-hubble-telescope/|archive-date=January 7, 2021}}</ref> The rest of the mission was devoted to photography and onboard experiments. To launch HST into an orbit that guaranteed longevity, ''Discovery'' entered an orbit of around {{cvt|613|xx|615|km}}. At one point during the mission, ''Discovery'' briefly reached an [[Apsis|apogee]] of {{cvt|621|km}}, the highest altitude ever reached by a Shuttle orbiter.<ref>{{cite tweet|number=1438322692097286151|user=planet4589|first=Jonathan|last=McDowell|title=Here is a comparison of the STS-31 and STS-82 TLE data (apogee and perigee given in 'conventional height', i.e. geocentric radius minus 6378&nbsp;km). STS-31 clearly a tiny bit higher, as can be seen in the zoomed-in second plot|url=https://twitter.com/planet4589/status/1438322692097286151|access-date=September 16, 2021}}</ref> The record height also permitted the crew to photograph Earth's large-scale geographic features not apparent from lower orbits. Motion pictures were recorded by two IMAX cameras, and the results appeared in the 1994 IMAX film ''[[Destiny in Space]]''.<ref name="Smithsonian IMAX Camera">{{cite web|title=Camera, ICBC, 70&nbsp;mm, IMAX|url=https://airandspace.si.edu/collection-objects/camera-icbc-70mm-imax/nasm_A20120259000|website=National Air and Space Museum|publisher=Smithsonian Institution|access-date=January 7, 2021|archive-url=https://web.archive.org/web/20210107122017/https://airandspace.si.edu/collection-objects/camera-icbc-70mm-imax/nasm_A20120259000 |archive-date=January 7, 2021|url-status=live}}</ref> Experiments on the mission included a biomedical technology study, advanced materials research, particle contamination and ionizing radiation measurements, and a student science project studying zero-gravity effects on electronic arcs. ''Discovery''{{'}}s reentry from its higher-than-usual orbit required a deorbit burn of 4 minutes and 58 seconds, the longest in Shuttle history up to that time.<ref name="STS-31 SSMR">{{cite web |date=May 1990 |title=STS-31 Space Shuttle Mission Report |url=https://ntrs.nasa.gov/api/citations/19920008146/downloads/19920008146.pdf |url-status=live |archive-url=https://web.archive.org/web/20210107114538/https://ntrs.nasa.gov/api/citations/19920008146/downloads/19920008146.pdf |archive-date=January 7, 2021 |publisher=NASA}} {{PD-notice}}</ref> ''Discovery'' orbited the [[Earth]] 80 times during the mission.<ref name="STS-31 SSMR" />

During the deployment of Hubble, one of the observatory's solar arrays stopped as it unfurled. While ground controllers searched for a way to command HST to unreel the [[Solar panels on spacecraft|solar array]], Mission Specialists McCandless and Sullivan began preparing for a contingency [[Extravehicular activity|spacewalk]] in the event that the array could not be deployed through ground control. The array eventually came free and unfurled through ground control while McCandless and Sullivan were pre-breathing inside the partially depressurized airlock.<ref name="Goodman 2009">{{cite conference|last1=Goodman |first1=John L.|last2=Walker |first2=Stephen R.|title=Hubble Servicing Challenges Drive Innovation of Shuttle Rendezvous Technique|url=https://ntrs.nasa.gov/api/citations/20090005185/downloads/20090005185.pdf |conference=32nd Annual AAS Guidance and Control Conference|conference-url=https://aas-rocky-mountain-section.org/|publisher=NASA|place=Breckenridge, Colorado|date=January 31, 2009|page=6|url-status=live|archive-url=https://web.archive.org/web/20210107132314/https://ntrs.nasa.gov/api/citations/20090005185/downloads/20090005185.pdf|archive-date=January 7, 2021}} {{PD-notice}}</ref>

Secondary payloads included the [[IMAX]] Cargo Bay Camera (ICBC) to document operations outside the crew cabin and a handheld IMAX camera for use inside the orbiter. Also included were the Ascent Particle Monitor (APM) to detect particulate matter in the payload bay; a Protein Crystal Growth (PCG) experiment to provide data on growing [[Protein crystallization|protein crystals]] in [[Micro-g environment|microgravity]], [[Radiation]] Monitoring Equipment III (RME III) to measure [[gamma ray]] levels in the crew cabin; Investigations into Polymer Membrane Processing (IPMP) to determine porosity control in the microgravity environment, and an [[Air Force Maui Optical and Supercomputing observatory|Air Force Maui Optical Site]] (AMOS) experiment.<ref name="STS-31 SSMR" />

The mission marked the flight of an {{cvt|5|kg}} [[human skull]], which served as the primary element of "Detailed Secondary Objective 469", also known as the In-flight Radiation Dose Distribution (IDRD) experiment. This joint NASA/[[United States Department of Defense|DoD]] experiment was designed to examine the penetration of [[radiation]] into the human cranium during spaceflight. The female skull was seated in a plastic matrix, representative of tissue, and sliced into ten layers. Hundreds of thermo-luminescent [[dosimeters]] were mounted in the skull's layers to record radiation levels at multiple depths. This experiment, which also flew on [[STS-28]] and [[STS-36]], was located in the shuttle's mid-deck lockers on all three flights, recording radiation levels at different orbital inclinations.<ref name="MacKnight 1991">{{cite book|last1=MacKnight|first1=Nigel|title=Space Year 1991: The Complete Record of the Year's Space Events|date=December 31, 1991|publisher=Motorbooks International|location=Osceola, Wisconsin|isbn=978-0-87938-482-1|page=41}}</ref>

''Discovery'' landed on Runway 22 at [[Edwards Air Force Base]] in [[California]] on April 29, 1990, at 13:49:57{{nbsp}}UTC (6:49:57{{nbsp}}am{{nbsp}}[[Pacific Daylight Time|PDT]], local time at the landing site). The landing had a rollout distance of {{cvt|2705|m}}, took 61 seconds, and marked the first use of carbon brakes on a shuttle. ''Discovery'' was returned to Kennedy Space Center after STS-31 on May 7, 1990.<ref name="Archives STS-31">{{cite web|last1=Ryba|first1=Jeanne|title=STS-31 |url=https://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-31.html|work=Mission Archives|publisher=NASA|archive-url=https://web.archive.org/web/20210107152149/https://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-31.html|archive-date=January 7, 2021|date=November 23, 2007|url-status=live}} {{PD-notice}}</ref>

{{LaunchAttempt
| date1           = 1990-04-10 08:47 AM
| result1         = Scrubbed
| reason1         = Technical
| decision_date1  = 
| decision_clock1 = −4:00
| weathergo1      = 
| notes1          = Faulty valve in auxiliary power unit.<ref name="MSER STS-31" />
| date2           = 1990-04-24, 08:33:51
| result2         = Successful
| reason2         = 
| decision_date2  = 
| decision_clock2 = 
| weathergo2      = 
| notes2          = Countdown was held at T−0:31 when a fuel valve line on ground support equipment failed to shut automatically. The valve was shut manually and the countdown was resumed.<ref name="MSER STS-31" />
}}