STS-37

STS-37, the eighth flight of the Space Shuttle Atlantis, was a six-day mission with the primary objective of launching the Compton Gamma Ray Observatory (GRO), the second of the Great Observatories program which included the visible-spectrum Hubble Space Telescope, the Chandra X-ray Observatory and the infrared Spitzer Space Telescope. The mission also featured two spacewalks, the first since 1985.

Spacewalks

 *  Ross and Apt  – EVA 1
 * EVA 1 Start: 7 April 1991
 * EVA 1 End: 7 April 1991
 * Duration: 4 hours, 26 minutes
 *  Ross and Apt  – EVA 2
 * EVA 2 Start: 8 April 1991
 * EVA 2 End: 8 April 1991
 * Duration: 5 hours, 47 minutes

Preparations and Launch
The STS-37 mission was successfully launched from launch pad 39B at 9:22:44AM EST on April 5, 1991 from the Kennedy Space Center in Florida. Resumption of the countdown after the T-9 minute hold was delayed about 4 minutes 45 seconds because of two possible weather-condition violations of the launch commit criteria (LCC). The first concerned the cloud ceiling being 500 feet less than the minimum of 8000 feet for a return-to-launch-site (RTLS) abort, and the second concerned the possible weather-condition (wind) effects on blast propagation. Both conditions were found acceptable and the launch countdown proceeded to a satisfactory launch to an inclination of 28.45 degrees. Launch weight: 116040 kg.

Compton Gamma Ray Observatory
The primary payload, the Gamma Ray Observatory (GRO), was deployed on flight day 3. GRO's high-gain antenna failed to deploy on command; it was finally freed and manually deployed by Ross and Apt during an unscheduled contingency space walk, the first since April 1985. The following day, the two astronauts performed the first scheduled space walk since November 1985 to test means for astronauts to move themselves and equipment about while maintaining the then-planned Space Station Freedom. GRO science instruments were Burst and Transient Source Experiment (BATSE), Imaging Compton Telescope (COMPTEL), Energetic Gamma Ray Experiment Telescope (EGRET) and Oriented Scintillation Spectrometer Experiment (OSSE). GRO was the second of NASA's four Great Observatories. The Hubble Space Telescope, deployed during Mission STS-31 in April 1990, was the first. GRO was launched on a two-year mission to search for the high-energy celestial gamma ray emissions, which cannot penetrate Earth's atmosphere. At about 35,000 pounds, GRO was the heaviest satellite to be deployed into low-Earth orbit from the Shuttle. It was also designed to be the first satellite that could be refueled in orbit by Shuttle crews. Five months after deployment, NASA renamed the satellite the Arthur Holly Compton Gamma Ray Observatory, or Compton Observatory, after the Nobel Prize-winning physicist who did important work in gamma ray astronomy.

Spacewalks
The first U.S. extravehicular activity (EVA) or spacewalk since 1985 was performed by Mission Specialists Jerry L. Ross and Jay Apt after six failed attempts to deploy the satellite's high-gain antenna. Repeated commands by ground controllers at the Payload Operations Control Center, Goddard Space Flight Center, Greenbelt, MD, and maneuvering of Atlantis and its Remote Manipulator System (RMS) robot arm, as well as GRO's antenna dish, were to no avail in dislodging the boom. Ross and Apt were prepared for such a contingency, and Ross freed the antenna boom within 17 minutes after beginning the spacewalk. It was the first unscheduled contingency EVA since STS-51-D in April 1985. Deployment occurred about 18:35 EST, approximately 4$1/2$ hours after it was scheduled.

The following day, on 8 April 1991, Ross and Apt made the first scheduled EVA since Mission STS-61-B in November 1985. The spacewalk was to test methods of moving crew members and equipment around the future Space Station Freedom. One of the experiments was to evaluate manual, mechanical and electrical power methods of moving carts around the outside of large structures in space. Although all three methods worked, the astronauts reported that propelling the cart manually or hand-over-hand worked best. With both EVAs, Ross and Apt logged 10 hours and 49 minutes walking in space during STS-37. Crew members also reported success with secondary experiments.

During the second EVA, a stainless steel palm restraint bar punctured the pressure bladder of Apt's right glove. However, the astronaut's hand and silk comfort glove partially sealed the hole, resulting in no detectable depressurization. In fact, the puncture was not noticed until postflight examination.

Additional Payloads and Experiments
Secondary payloads included Crew and Equipment Translation Aids (CETA), which involved scheduled six-hour space walk by astronauts Ross and Apt (see above); Ascent Particle Monitor (APM); Shuttle Amateur Radio Experiment II (SAREX II); Protein Crystal Growth (PCG); Bioserve/Instrumentation Technology Associates Materials Dispersion Apparatus (BIMDA); Radiation Monitoring Equipment III (RME Ill); and Air Force Maui Optical Site (AMOS) experiment. Among the other payloads flown was the first flight of the Bioserve/Instrumentation Technology Associates Materials Dispersion Apparatus (BIMDA) to explore the commercial potential of experiments in the biomedical, manufacturing processes and fluid sciences fields, and the Protein Crystal Growth experiment, which has flown eight times before in various forms. Astronaut Pilot Kenneth Cameron was the primary operator of the Shuttle Amateur Radio Experiment (SAREX), although all five crew members participated as amateur radio operators. It was arguably the first time that the astronauts received fast scan amateur television video from the ham radio club station (W5RRR) at JSC.

Landing
11 April 1991, 06:55:29 PDT, Runway 33, Edwards Air Force Base, CA. Rollout distance: 6,364 feet. Rollout time: 56 seconds. Landing originally scheduled for 10 April 1991, but delayed one day due to weather conditions at Edwards and Kennedy Space Center (KSC). Orbiter returned to KSC 18 April 1991. Landing weight: 86227 kg.

Due to an incorrect call on winds aloft, Atlantis landed 623 feet short of the lakebed runway's threshold marking. This did not present a problem, since the orbiter landed on the dry lake bed of Edwards, and a problem was not obvious to most viewers. Had the landing been attempted at the Kennedy Space Center, the result would have been a touchdown on the paved underrun preceding the runway and would have been much more obvious. Landing speed was 168 KEAS, 13 knots faster than the slowest landing of the Shuttle program, STS-28's 155 KEAS.

Mission insignia
The three stars on the top and seven stars on the bottom of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence. The stars also represented the Amateur Radio term "73" or "Best regards", consistent with the fact that the entire crew had become licensed and operated the SAREX experiment while on orbit.