NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

USA 40



The US Air Force's second generation classified Satellite Data System (SDS-2) replaced the SDS-1 system starting with its first launch in 1989 of USA 40. Like its predecessors, the SDS-2 spacecraft had high apogee and low perigee, enabling it to cover the polar regions for Air Force communications in those areas. The SDS-2, however, had an additional package, the Heritage (Radiant Agate) infrared early warning system for detection of ballistic missile launches. The Shuttle payload envelope defined the satellite's design. It featured two 15-foot diameter dish antennas adapted by Hughes from its TDRSS-3 satellite design. It also had a third dish (6.6 feet in diameter) that served as a k-band antenna downlink. It had two more antennas, one that was used for uplink communications, and another that was a telemetry and command antenna, which was used as a backup. The body itself, based on LEASAT, was cylindrical and was 14 feet in diameter and 9.5 feet long. Its solar arrays generated 1238 watts of power with support from three 25-amp-hour nickel-cadium batteries.

Alternate Names

  • 20167
  • SDS-2
  • USA40

Facts in Brief

Launch Date: 1989-08-08
Launch Vehicle: Shuttle
Launch Site: Cape Canaveral, United States
Mass: 700 kg

Funding Agency

  • Department of Defense-Department of the Air Force (United States)


  • Surveillance and Other Military

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office

[] NASA Logo -