SHUTTLE OPERATIONS

Before its first flight, the Space Shuttle was designated the nation's primary vehicle for access to space. This policy was changed after the Challenger accident to encourage use of expendable rockets for some missions. The Shuttle has flown scores of successful missions, many of them to deploy payloads for various customers. Most were communications satellites; the others were scientific and classified military payloads.

MILITARY MISSIONS

The military was an early user of the Space Shuttle. By 1990 eight classified satellites were deployed from the Shuttle for electronic intelligence, photographic and radar reconnaissance, and defense communications. Since then, classified military satellites have been launched by expendable rockets. The Department of Defense also used the Shuttle occasionally for unclassified research payloads when a crew was needed.

Air Force Payload #675, an unclassified early warning satellite, was launched on STS-39 in 1991.

COMMERCIAL PAYLOADS

The Shuttle has launched dozens of communications satellites for paying customers, including foreign governments and American companies. It has also been used to carry scientific experiments for private industry and to retrieve failed commercial satellites.

The high cost of Shuttle launches and changes in policy have led industry to turn again to expendable launch vehicles for access to space. Commercial satellites are being launched on privately owned and operated rockets.

The first commercial satellite released from the Shuttle was SBS-3, for Satellite Business Systems, on the STS-5 mission in 1982.