Mainstream Shuttle operations

The main Shuttle program changed emphasis again to more scientific missions, many of which were linked to the forthcoming ISS program. Within the decade, there were 63 Shuttle missions, including the 10 missions associated with Mir (the “near Mir” rendezvous mission of STS-63 and 9 docking missions STS-71, 74, 76, 79, 81, 84, 86, 89, and 91), and the first 6 ISS assembly missions (STS-88, 96, 101, 106, 92, and 97). The remaining missions were aimed at catching up with the delayed manifest and providing information useful to the proposed research programs on the ISS.

The classified military Shuttle missions quickly came to an end. In fact, the three which were flown (STS-39, STS-44, and STS-53) were only partially classi­fied. The Shuttle also continued its program of deployments of NASA’s Great Observatories, as well as larger payloads such as the Compton Gamma Ray Observatory (STS-37), the Upper Atmosphere Research Satellite (STS-48), the Advanced Communications Technology Satellite (STS-51), and the Chandra X-Ray Observatory (STS-93).

After the deployment of Hubble in 1990, problems were discovered with its optical clarity. Corrective optics were designed and these had to be installed on the first of a series of planned servicing missions. Within this decade of operations, there were three such missions to Hubble (STS-61, 82, and 103), which featured a total of 13 EYAs working at the telescope.

The Shuttle program of the 1990s also included a number of Spacelab module or pallet missions, which utilized the Shuttle’s unique capabilities for science in low Earth orbit. Between 1991 and 2000, these missions and payloads included: Space Life Science 1 (STS-40) and 2 (STS-58) and the advanced Neurolab (STS-90); the International Microgravity Laboratory 1 (STS-42) and 2 (STS-65); Atmospheric Laboratory for Applications and Science 1 (STS-45), 2 (STS -56), and Atlas 3 (STS-66); U. S. Microgravity Laboratory 1 (STS-50) and 2 (STS-73); the U. S. Microgravity Payload 1 (STS-52), 2 (STS-62), 3 (STS-75), and 4 (STS-87); Space Radar Laboratory 1 (STS-59), 2 (STS-68), and the advanced Shuttle Radar Topography Mission (STS-99); the Japanese Spacelab J (STS-47) and the German Spacelab D2 (STS-55); Astro-2 (STS-67); the Life and Micro­gravity Spacelab (STS-78); and the Material Sciences Laboratory 1 (STS-83) and its re-flight (STS-94).

Contingency spacewalking had been an option for emergency or unplanned situations since the start of the program, so each Shuttle crew featured an EVA – trained team, whether for planned or unplanned space walks. The first Shuttle EVA had occurred during STS-6 in 1983 and since then EVA had supported a number of satellite-servicing and recovery/repair operations. Now, additional EVAs were being added to the program to evaluate hardware, training, procedures, and operations planned for the ISS.

Several Shuttle flights included demonstrations and evaluations of techniques and equipment in preparation for the ISS assembly missions, which would begin in 1998. Once that huge construction program started, the Shuttle program shifted emphasis again, beginning in 1999 and for the rest of its operational service, from mainly science to mostly ISS assembly and resupply. In fact, during the period of station assembly (November 1998-July 2011), there were only six missions (STS-93, 103, 99, 109, 107, and 125) which were not directly related to the ISS out of 43 Shuttle missions completed.