STS-31

Space Shuttle Discovery launches into the sky at the start of STS-31, while, for the first time since 1986, a second shuttle, Columbia, waits for her chance to launch.

HST in the cargo bay.

STS-31 was launched on 24 April 1990 at 8:33:51 am EDT. A launch attempt on 10 April 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 ordered the valve closed and the countdown continued.[4]

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 highest orbit up to that date, in order for HST to be released near its operational altitude well outside the atmosphere. Discovery orbited the Earth 80 times during the mission.[5]

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 and near-infrared wavelengths. The Hubble mission was a joint NASA-ESA effort going back to the late 1970s.[6] 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 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 1994 IMAX film Destiny in Space.[7] Experiments 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.[5]

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 array, Mission Specialists McCandless and Sullivan began preparing for a contingency 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.[8]

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 crystals in 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 Site (AMOS) experiment.[5]

The mission marked the flight of an 11-pound 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/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.[9]

Discovery landed on 29 April 1990 at 6:49:57 am PDT, landing on Runway 22 at Edwards Air Force Base in California. The rollout distance was 2,705 metres (8,875 ft) and took 61 seconds. This also marked the first use of carbon brakes. Discovery returned to KSC on 7 May 1990.[10]

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.[11]

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  Hubble at the pad.
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  Liftoff of Discovery with the Hubble Space Telescope on board.
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  Low hover position.
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  High over Cuba.
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  Solar array deployment.
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  Hubble drifts away over Peru.
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  Florida and the Bahamas.
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  Discovery returns home.

• List of human spaceflights
• List of Space Shuttle missions
• Outline of space science
• Space Shuttle

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.

Wikimedia Commons has media related to STS-31.

• NASA mission summary
• STS-31 Video Highlights