Satellite Data System

The current SDS-3 constellation, consisting of three Molniya orbit type and two geostationary satellites

The Satellite Data System (SDS) is a system of United States military communications satellites. At least three generations have been used: SDS-1 from 1976 to 1987; SDS-2 from 1989 to 1996; SDS-3 from 1998 to the present. It is believed that these satellites were known by the code name Quasar.^[1] The first generation were named simply 'SDS', the second generation were named 'Quasar' and the third generation each carried their own designation names.^[2]

Orbital characteristics

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. In addition, two geostationary satellites appear to be part of the system. The SDS satellites were constructed by Hughes Aircraft.

Mission

The primary purpose of the SDS satellites is to relay imagery from low-flying reconnaissance satellites, notably the Keyhole optic reconnaissance and Lacrosse/Onyx radar reconnaissance satellites to ground stations in the United States.^[3]

SDS-1

Releasable Picture of NRO satellite, possible SDS-1

The SDS 3-4 satellite (USA 179, 2004-034A) created a tiny trail perpendicular to the star trails in this 10 second exposure with a Zeiss Sonnar MC 2.8/180mm lens made by amateur satellite observer Marco Langbroek

Each SDS-1 satellite had 12 channels available for ultra-high frequency communication. They were cylindrical in shape, roughly 25 feet (7.6 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.^[4]

SDS-2

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 several satellites, possibly on missions STS-28, STS-38, and STS-53. Other launches have used the Titan-4 rocket.

SDS-3

Satellites

Name	COSPAR ID^[5] SATCAT №	Launch date	Launch vehicle	Launch site	NROL designation	Remarks

OPS 7837	1976-050A 08871	1976-06-02	Titan III(34)B	VAFB SLC-4W	N/A
OPS 7940	1976-080A 09270	1976-08-06	Titan III(34)B	VAFB SLC-4W
OPS 7310	1978-075A 10993	1978-08-05	Titan III(34)B	VAFB SLC-4W
OPS 5805	1980-100A 12093	1980-12-13	Titan III(34)B	VAFB SLC-4W
USA-4	1984-091A 15226	1984-08-28	Titan III(34)B	VAFB SLC-4W
USA-9	195-014A 15546	1985-02-08	Titan III(34)B	VAFB SLC-4W
USA-21	1987-015A 17506	1987-02-15	Titan III(34)B	VAFB SLC-4W

USA-40	1989-061B 20167	1989-06-02	Space Shuttle Columbia STS-28/Orbus-21S	KSC LC-39B	N/A
USA-67	1990-097B 20963	1990-11-15	Space Shuttle Atlantis STS-38/Orbus-21S	KSC LC-39A		Geosynchronous satellite, deployed along with Prowler and initially misidentified as a Magnum SIGINT spacecraft
USA-89	1992-086B 22518	1992-12-02	Space Shuttle Discovery STS-53/Orbus-21S	KSC LC-39A
USA-125	1996-038A 23945	1996-07-03	Titan IV(405)A	CCAFS LC-40

USA-137	1998-005A 25148	1998-01-29	Atlas IIA	CCAFS SLC-36A	NROL-5	Capricorn
USA-155	2000-080A 26635	2000-12-06	Atlas IIAS	CCAFS SLC-36A	NROL-10	Great Bear, geosynchronous satellite at 10° West
USA-162	2001-046A 26948	2001-10-11	Atlas IIAS	CCAFS SLC-36B	NROL-12	Aquilla, geosynchronous satellite at 144° West
USA-179	2004-034A 28384	2004-08-31	Atlas IIAS	CCAFS SLC-36A	NROL-1	Nemesis, final Atlas II launch
USA-198	2007-060A 32378	2007-12-10	Atlas V 401	CCAFS SLC-41	NROL-24	Scorpius
USA-227	2011-011A 37377	2011-03-11	Delta IV-M+(4,2)	CCAFS SLC-37B	NROL-27	Gryphon, geosynchronous satellite at 10° West, replaced USA-155
USA-236	2012-033A 38466	2012-06-20	Atlas V 401	CCAFS SLC-41	NROL-38	Drake, geosynchronous satellite at 144° West, replacement for USA-162
USA-252	2014-027A 39751	2014-05-22	Atlas V 401	CCAFS SLC-41	NROL-33	Geosynchronous satellite

References

↑ Jonathan's Space Report: NRO Satellite Names
↑ Jonathan's Space Report: Satellite Catalogue
↑ Richelson J.T., 2001: The Wizards of Langley. Inside the CIA's Directorate of Science and Technology. Westview press, Boulder
↑ National Reconnaissance Office: "NRO Brochure circa 1997"
↑ Jonathan's Space Report: List of satellite launches

Vick, Berman, Lindborg, Fellow (March 19, 1997). SDS-1 Military Communications Satellite. Federation of American Scientists. Accessed April 24, 2004.
Vick, Berman, Lindborg, Fellow, Pike, Aftergood (March 19, 1997). SDS-2 Military Communications Satellite. Federation of American Scientists. Accessed April 24, 2004.

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