||This article needs additional citations for verification. (May 2009)|
|Distance travelled||3,328,466 kilometres (2,068,213 mi)|
|Spacecraft||Space Shuttle Discovery|
|Launch mass||117,586 kilograms (259,230 lb)|
|Landing mass||85,947 kilograms (189,480 lb)|
|Payload mass||11,878 kilograms (26,190 lb)|
|Start of mission|
|Launch date||24 April 1990, 12:33:51UTC|
|Launch site||Kennedy LC-39B|
|End of mission|
|Landing date||29 April 1990, 13:49:57UTC|
|Perigee||585 kilometres (364 mi)|
|Apogee||615 kilometres (382 mi)|
STS-31 was the thirty-fifth mission of the American Space Shuttle program, which launched the Hubble Space Telescope astronomical observatory into Earth orbit. The mission used the Space Shuttle Discovery, which lifted off from Launch Pad 39B on 24 April 1990 from Kennedy Space Center, Florida.
Discovery's crew deployed the telescope on 25 April, and spent the rest of the mission tending to various scientific experiments in the shuttle's payload bay and operating a set of IMAX cameras to record the mission. Discovery's launch marked the first time since January 1986 that two Space Shuttles had been on the launch pad at the same time – Discovery on 39B and Columbia on 39A.
|Commander||Loren J. Shriver
|Pilot||Charles F. Bolden, Jr.
|Mission Specialist 1||Steven A. Hawley
|Mission Specialist 2||Kathryn D. Sullivan
|Mission Specialist 3||Bruce McCandless II
Second and last spaceflight
Crew Notes 
Initially, this mission was to be flown in August 1986 as STS-61-J using Atlantis, but was postponed due to the Challenger disaster. John Young was originally assigned to command this mission, which would have been his seventh spaceflight, but was reassigned to an administrative position and was replaced by Loren Shriver.
Mission highlights 
Launched 24 April 1990, 8:33:51 am EDT. Launch scheduled for 18 April, then 12 April, then 10 April, following Flight Readiness Review (FRR). First time date set at FRR was earlier than that shown on previous planning schedules. Launch 10 April scrubbed at T-4 minutes due to faulty valve in auxiliary power unit (APU) number one. APU replaced and payload batteries recharged. Countdown briefly halted at T-31 seconds when computer software failed to shut down a fuel valve line on ground support equipment. Engineers ordered valve to shut and countdown continued. Launch Weight: 112,994 kilograms (249,110 lb).
The primary payload was the Hubble Space Telescope (HST), deployed in a 380 statute mile (612 kilometres (380 mi)) orbit. The shuttle's orbit in this mission was its second highest orbit up to that date, in order that the HST could be released near to its operational altitude well outside of the atmosphere. Discovery orbited the earth 80 times during the mission.
The main purpose of this mission was to deploy the Hubble Space Telescope (HST) astronomical observatory. It was designed to operate above the Earth's turbulent and obscuring atmosphere to observe celestial objects at ultraviolet, visible and near-infrared wavelengths. This was a joint NASA-ESA effort. The rest of the mission was devoted to photography and onboard experiments. To launch HST into an orbit that guaranteed longevity, Discovery soared to 600 kilometres (370 mi) – the highest shuttle altitude ever at the time. The record height 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 IMAX film Destiny in Space. Experiment activity included a biomedical technology study, advanced materials research; particle contamination and ionizing radiation measurements; and 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 min 58 s, the longest in shuttle history up to that time.
Secondary payloads: IMAX Cargo Bay Camera (ICBC) to document operations outside crew cabin and hand-held IMAX camera for use inside crew cabin; Ascent Particle Monitor (APM) to detect particulate matter in payload bay; Protein Crystal Growth (PCG) to provide data on growing protein crystals in microgravity; Radiation Monitoring Equipment III (RME III) to measure gamma ray levels in crew cabin; Investigations into Polymer Membrane Processing (IPMP) to determine porosity control in microgravity environment; Shuttle Student Involvement Program (SSIP) experiment to study effects of near-weightlessness on electrical arcs, and Air Force Maui Optical Site (AMOS) experiment.
29 April 1990, 6:49:57 am PDT, Runway 22, Edwards Air Force Base, CA. Rollout distance: 2,705 metres (8,875 ft). Rollout time: 61 seconds. First use of carbon brakes at landing. Orbiter returned to KSC on 7 May 1990. Landing Weight: 85,782 kilograms (189,120 lb).
|Attempt||Planned||Result||Turnaround||Reason||Decision point||Weather go (%)||Notes|
|1||10 Apr 1990, 12:00:00 am||scrubbed||---||technical||(TT-4)||faulty valve in Auxiliary Power Unit (APU) Number One.|
|2||24 Apr 1990, 12:00:00 am||delayed, successful||14 days, 0 hours, 0 minutes||technical||(TT-31 seconds)||countdown was held at T-31 seconds when a fuel valve line on ground support equipment failed to shut automatically. The valve was shut manually and the countdown was resumed.|
Wake-up calls 
NASA began a tradition of playing music to astronauts during the Gemini program, which was first used to wake up a flight crew during Apollo 15. Each track is specially chosen, often by their families, and usually has a special meaning to an individual member of the crew, or is applicable to their daily activities.
|Day 2||"Space is Our World"||Private Numbers|
|Day 3||"Shout"||Otis Day and the Knights|
|Day 4||"Kokomo"||Beach Boys|
|Day 5||"Cosmos"||Frank Hayes|
|Day 6||"Rise and Shine"||Raffi|
Florida and the Bahamas.
See also 
- Space science
- Space shuttle
- List of space shuttle missions
- List of human spaceflights chronologically
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