STS-82 is the second of four planned servicing missions for the orbiting Hubble Space Telescope (HST), which has rewritten the astronomy textbooks since its deployment nearly seven years ago.

The primary mission objectives are to retrieve, service and then re-deploy HST. Depending on the orbiter’s available fuel, the seven-member crew also will use Discovery’s Vernier Reaction Control System jets to boost the bus-sized Hubble to an orbit slightly higher -- by 1 to 5 nautical miles (1.8 to 9 kilometers) -- to prolong its orbital life and compensate for the slow decay of its approximately 320-nautical-mile-high (593-kilometer) orbit above Earth.

Four of the seven crew members will be divided into two teams to perform the scheduled four extravehicular activities (EVAs) or spacewalks required for the servicing.

The first servicing, on STS-61 in December 1993, was one of the most challenging and complex manned missions ever attempted by NASA. During that 11-day flight, a record five back-to-back spacewalks were performed to install new hardware and instruments, some of which corrected a flaw in Hubble’s main mirror. The more than 24,000-pound (10,886-kilogram) HST was deployed by the five-member STS-31 crew in April 1990. Servicing missions also are planned in 1999 and 2002.

On STS-82, astronauts will replace two outdated scientific instruments with two new instruments on HST: the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) will take the place of the Faint Object Spectrograph; and the Space Telescope Imaging Spectrograph (STIS) will be installed, after the removal of the Goddard High Resolution Spectrograph.

Among other planned changes to enhance the science capabilities of HST are the replacement of a reaction wheel assembly, two tape recorders, a data interface unit and solar array electronics; and installation of a refurbished fine guidance sensor and magnetometer covers.

Among Hubble’s most important scientific discoveries since it became operational in 1990 are: the first conclusive evidence for the existence of massive black holes; detection of light emitted from distant galaxies when the universe was only 5 percent of its current age; evidence that the universe may be much younger than has been previously thought; revealing of dynamic weather changes on nearly all planets; and discovery of disks that might be embryonic planetary systems around young stars, implying that planets, and presumably life, may be abundant in the universe.

STS-82, the second of eight planned Shuttle missions for 1997, will be the 22nd flight of Discovery (OV-103). Discovery last flew on STS-70 in 1995; it was then sent to California for a period of refurbishment and modification.

The 82nd Space Shuttle launch will begin with liftoff from Pad A, Launch Complex 39. Discovery will ascend at a 28.45-degree inclination to the equator for direct insertion to a 362-statute-mile (314-nautical-mile/582- kilometer) orbit. The 10-day mission is scheduled to conclude with a landing at KSC’s Shuttle Landing Facility.

Three-time space flyer Kenneth D. Bowersox (Cmdr., USN) will lead the experienced seven-member crew as mission commander. He was the pilot of STS-50 in 1992 and the first Hubble servicing mission, STS-61, in 1993, and commander of STS-73 in 1995.

Assisting him at the orbiter controls will be Pilot Scott J. "Doc" Horowitz (Lt. Col., USAF). He flew once before, as pilot of STS-75 in 1996.

The payload commander will be Mark C. Lee (Col., USAF), a veteran of three space flights. He was the payload commander of STS-47 in 1992 and a mission specialist on STS-30 in 1989 and on STS-64 in 1994, during which he performed the first untethered spacewalk in 10 years while testing a self-rescue jetpack.

For STS-82, NASA has paired two experienced spacewalkers with astronauts who have not yet performed an EVA.

Joining Lee on the first and third spacewalks of this mission will be Mission Specialist Steven L. Smith, who also flew on STS-68 in 1994 as a mission specialist.

Performing the second and fourth spacewalks will be Mission Specialists Gregory J. Harbaugh and Joseph R. "Joe" Tanner. Harbaugh has flown three times as a mission specialist, on STS-39 in 1991, on STS-54 in 1993 and on STS-71 in 1995. He did an EVA on STS-54.

Tanner was a mission specialist on STS-66 in 1994. This will be his first spacewalk.

Steven A. Hawley, who has two degrees in astronomy, also will fly on STS-82 as a mission specialist, as well as the flight engineer. He has primary responsibility for operation of the orbiter’s Remote Manipulator System (RMS) arm -- both for capture and redeployment of HST and as a work platform for the spacewalkers. He will manipulate the robot arm from controls inside the orbiter. He used the RMS arm to deploy the Hubble Space Telescope on STS-31 in 1990.

Three-time space flyer Hawley also was a mission specialist on STS-41D in 1984 and on STS-61C in 1986. He was deputy chief of the Astronaut Office before leaving in 1990 to assume the post of associate director of NASA’s Ames Research Center in California. He came back to JSC in 1992 as deputy director of Flight Crew Operations, and was returned to astronaut flight status in early 1996.

Rendezvous with and grapple of HST is scheduled to occur on Flight Day 3. The crew will use the orbiter’s robotic arm to capture HST and berth it in in the Shuttle bay on the HST Flight Support System.

Although Hubble was built with handholds and other accessories to enable spacewalking astronauts to service it, the crew also will have more than 150 crew aids and tools, known as space support equipment (SSE). The EVAs will begin on Flight Day 4 and continue through Flight Day 7. The reboost probably will be done in stages, spread out over two or more days at the end of EVAs. The re-deployment of HST is planned on Flight Day 8.

Besides Hawley, Lee and Harbaugh are trained to operate the RMS arm for the spacewalks. When the Lee-Smith team is conducting an EVA, Tanner will be the Intravehicular (IV) crew member who oversees the spacewalk from inside Discovery; when the Harbaugh-Tanner team is performing an EVA, Smith will be the IV crew member. During an EVA, the spacewalking team members will take turns as a "free floater" on a safety tether or anchored at the end of the RMS arm.

A brief description of the major planned activities on each of the six-hour spacewalks follows:

EVA 1, Flight Day 4, Lee and Smith: The two new scientific instruments, NICMOS AND STIS, will be installed, taking the place of two instruments which were designed and built more than two decades ago as part of the original Hubble.

Both NICMOS and STIS are about the size of refrigerators. NICMOS, which weighs approximately 815 pounds (370 kilograms), is HST’s first cryogenic instrument -- its sensitive infrared detectors must operate at very cold temperatures of minus 355 degrees Fahrenheit or 58 degrees Kelvin. Frozen nitrogren ice inside a cryogenic dewar is designed to cool the detector for up to five years. The University of Arizona under contract with NASA’s Goddard Space Flight Center (GSFC) headed the development of NICMOS. STIS has the major capabilities of the two spectrographs which will be removed from HST, as well as new technological features such as two-dimensional spectroscopy. The Laboratory for Astronomy and Solar Physics at GSFC headed the development of STIS.

EVA 2, Flight Day 5, Harbaugh and Tanner: A major task will be to change out one of three fine guidance sensors (FGS) on Hubble with an upgraded spare weighing about 485 pounds (220 kilograms). Two FGSs are used to point the telescope at an astronomical object and hold the target in the HST instrument’s field of view. The third FGS can be used as a scientific instrument for celestial measurements.

Also planned that day are the replacement of the optical electronics enhancement kit and the engineering/science tape recorder-2. The latter is one of three mechanical, reel-to-reel tape recorders which records all science data from Hubble. The outdated recorder has failed.

EVA 3, Flight Day 6, Lee and Smith: Several important tasks will be performed, including the replacement of the data interface unit-2, and the engineering/science tape recorder-1 with the solid state recorder. Unlike the current HST tape recorders, the digital solid state recorder has no moving parts to wear out. It also is more flexible than a reel-to-reel recorder and can store more than 10 times as much data.

Also scheduled for the third EVA, if it could not be accomplished by Lee and Smith during the first spacewalk, is the changeout of the reaction wheel assembly. One of Hubble’s four reaction wheel assemblies recently failed. HST has no propellant for attitude control; the reaction wheel assemblies help to maneuver it.

EVA 4, Flight Day 7, Harbaugh and Tanner: The final scheduled EVA will feature the replacement of the solar array drive electronics-2 (SADE-2) and installation of the new upgraded magnetic sensing system covers.

HST has two SADE boxes which control the solar arrays. One of them had some transistor failures and was changed out during the first servicing mission. That SADE was fixed and now will replace one of the boxes currently on Hubble. The new magnetometer covers will replace the makeshift wrapping which was installed by the first servicing crew and has since degraded.