Replacement for the SDS satellites, which from Molniya-type orbits, provided data relay services for optical reconnaissance and other military spacecraft. They were launched by the Shuttle/IUS or by the Titan IV, which implies a satellite mass of around 6000 kg, compared to only 700 kg for the earlier SDS satellites. They therefore probably included other reconnaissance payloads as well (signals intelligence, early warning, weather monitoring, etc).

Typical orbit: Believed 400 x 38000 km, 63.2 deg inclination. Mass: 6,000 kg (13,200 lb). Associated Launch Vehicle: Shuttle, Titan 4.

• 1989 August 8 - USA 40 - Launch Site: Cape Canaveral. Launch Vehicle: Shuttle. Mass: 5,900 kg (13,000 lb). Perigee: 296 km (183 mi). Apogee: 307 km (190 mi). Inclination: 57.00 deg. Period: 90.50 min.

  Deployed from STS-28 8 August 1989.

• 1992 December 2 - USA 89 - Launch Site: Cape Canaveral. Launch Vehicle: Shuttle. Mass: 5,900 kg (13,000 lb). Perigee: 366 km (227 mi). Apogee: 377 km (234 mi). Inclination: 56.90 deg. Period: 92.00 min.

  Deployed from STS-53 12/2/92.

• 1996 July 3 - USA 125 - Launch Site: Cape Canaveral. Launch Vehicle: Titan 4. Mass: 6,300 kg (13,800 lb). Perigee: 292 km (181 mi). Apogee: 319 km (198 mi). Inclination: 54.90 deg. Period: 90.63 min.

  Unknown orbit

• 1996 May 12 - USA 119 - Launch Site: Vandenberg. Launch Vehicle: Titan 4. Mass: 6,300 kg (13,800 lb). Perigee: 1,051 km (653 mi). Apogee: 1,165 km (723 mi). Inclination: 63.40 deg. Period: 107.44 min.

  Unknown orbit

• McDowell, Jonathan, Launch Log, October 1998. Jonathan McDowell's complete on-line listing of all objects orbited since Sputnik. Accessed at: http://hea-www.harvard.edu/~jcm/space/log/launch.html.

• NASA/GSFC Orbital Information Group Website, . Accessed at: http://oig1.gsfc.nasa.gov/.

• Space-Launcher.com, Orbital Report News Agency. Accessed at: http://www.orbireport.com/Log.html.

• National Space Science Center Planetary Page, As of 19 February 1999.. Accessed at: http://nssdc.gsfc.nasa.gov/planetary/planetary_home.html.

• Krebs, Gunter, Gunter's Space Page, University of Frankfurt, 1996. Accessed at: http://www.skyrocket.de/space.

• McDowell, Jonathan, Jonathan's Space Report (Internet Newsletter), Harvard University, Weekly, 1989 to Present. Essential internet newsletter recording worldwide weekly space events. Accessed at: http://www.planet4589.org/jsr.html.

• USAF Satellite Database, USAF Institute of Technology, 1995. Accessed at: ftp://archive.afit.af.mil/pub/space/.

• McDowell, Jonathan, Jonathan's Space Home Page, Harvard University, 1997-present. Jonathan McDowell's complete on-line listing of all objects orbited and over 20,000 rocket launches Accessed at: http://www.planet4589.org/jsr.html.

• JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Accessed at: http://msl.jpl.nasa.gov/home.html.