 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.jonathan's space report: nro satellite names the first generation were named simply 'sds', the second generation were named 'quasar' and the third generation each carried their own designation names.jonathan's space report: satellite catalogue ==orbital characteristics== sds satellites have a highly elliptical orbit, going from about 300 kilometers at perigee to roughly 39,000&nbsp;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.richelson j.t., 2001: the wizards of langley. inside the cia's directorate of science and technology. westview press, boulder ==sds-1== thumb|right|releasable picture of nro satellite, possible sds-1thumb|right|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  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.national reconnaissance office: "nro brochure circa 1997" ==sds-2== the sds-2 is significantly more massive at 5150 pounds (2335&nbsp;kg), with three separate communica
Communications_satellites Hughes_Aircraft_Company