Satellite Data System

The Satellite Data System (SDS) is a system of United States military communications satellites. At least two generations have been used: SDS-1 from July 1976 to November 1995, and SDS-2 from 1989 to the present. SDS satellites have a highly elliptical orbit, going from about 300 kilometers at perigee to roughly 39,000 km at apogee in order to allow communications with polar stations that cannot contact geosynchronous satellites. The high apogee meant that the polar regions were visible for long amounts of time, and only two satellites were required in order to achieve constant communications ability. The SDS satellites were constructed by Hughes Aircraft.

The primary purpose of the SDS satellites is to relay imagery from low-flying reconnaissance satellites to ground stations in the United States.

Each SDS-1 satellite had 12 channels available for ultra-high frequency communication. They were cylindrical in shape, roughly convert|25|ft|m long. 980 watts of electrical power were available from solar panels and batteries. The SDS-1 had a mass of 1385 pounds (630 kilograms) and was launched on Titan-3B rockets. The SDS-1 satellites had similar orbits to the Air Force's Jumpseat ELINT satellites.

The SDS-2 is significantly more massive at 5150 pounds (2335 kg), with three separate communication dishes, including one for a K band downlink. Two dishes are 15 feet (4.5 meters) in diameter, while the third is 6.6 feet (2 m) in diameter. The solar arrays generate 1238 watts of power. It is believed that the Space Shuttle has been used to launch one or two satellites, possibly one on STS-28, and another on STS-53. Other launches have used the Titan-4 rocket.

"Quasar" is the rumored code name for the communications satellite.

A recent Quasar may have been launched into a high-apogee orbit from Cape Canaveral on August 31, 2004 by an Atlas 2AS rocket.

Launches

DS-1

*SDS F-1 launched 1976-06-02 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1976-050A 1976-050A] (OPS-7837)
*SDS F-2 launched 1976-08-06 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1976-080A 1976-080A] (OPS-7940)
*SDS F-3 launched 1978-08-05 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1978-075A 1978-075A] (OPS-7310)
*SDS F-4 launched 1981-04-24 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1981-038A 1981-038A] (OPS-7225)
*SDS F-5A launched 1984-08-28 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1984-091A 1984-091A] (USA-4)
*USA-9 launched 1985-02-08 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1985-014A 1985-014A] (USA-9)
*SDS F-6 launched 1987-02-12 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1987-015A 1987-015A] (USA-21)

DS-2

*USA-40 launched 1989-08-08 on STS-28 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1989-061B 1989-061B] (USA-40)
*USA-67 launched 1990-11-15 on STS-38 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1990-097B 1990-097B] )(USA-67)(Some sources identify USA-67 as a Magnum SIGINT satellite)
*USA-89 launched 1992-12-02 on STS-53 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1992-086B 1992-086B] (USA-89)
*USA-125 launched by Titan IV 1996-07-03 [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1996-038A 1996-038A] (USA-125)

DS-3

*USA-137 "Capricorn" launched by Atlas IIA 1998-01-29
*USA-155 "Great Bear" launched by Atlas IIAS 2000-12-06
*USA-162 "Aquilla" launched by Atlas IIAS 2001-10-11
*USA-179 "Nemesis" launched by Atlas IIAS 2004-08-31
*USA-198 "Scorpius" launched by Atlas V 401 2007-12-10

References

*Vick, Berman, Lindborg, Fellow (March 19, 1997). [http://www.fas.org/spp/military/program/com/sds_1.htm SDS-1 Military Communications Satellite] . "Federation of American Scientists". Accessed April 24, 2004.
*Vick, Berman, Lindborg, Fellow, Pike, Aftergood (March 19, 1997). [http://www.fas.org/spp/military/program/com/sds_2.htm SDS-2 Military Communications Satellite] . "Federation of American Scientists". Accessed April 24, 2004.