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The Satellite Data System (SDS) is a system of United States military communications satellite
Communications satellite

A communications satellite is an artificial satellite stationed in space for the purposes of telecommunications. Modern communications satellites use a variety of orbits including geostationary orbits, Molniya orbits, other elliptical orbits and low Earth orbits....
s. 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. SDS satellites have a highly elliptical orbit
ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
, going from about 300 kilometers at perigee to roughly 39,000 km at apogee in order to allow communications with polar
Geographical pole

A geographical pole , is either of two points on the surface of a spinning planet or other spinning body, at 90 degrees from its equator, at one of the two points where the Axis of rotation around which the body spins meets the surface of the body....
 stations that cannot contact geosynchronous satellites.






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The Satellite Data System (SDS) is a system of United States military communications satellite
Communications satellite

A communications satellite is an artificial satellite stationed in space for the purposes of telecommunications. Modern communications satellites use a variety of orbits including geostationary orbits, Molniya orbits, other elliptical orbits and low Earth orbits....
s. 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. SDS satellites have a highly elliptical orbit
ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
, going from about 300 kilometers at perigee to roughly 39,000 km at apogee in order to allow communications with polar
Geographical pole

A geographical pole , is either of two points on the surface of a spinning planet or other spinning body, at 90 degrees from its equator, at one of the two points where the Axis of rotation around which the body spins meets the surface of the body....
 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
Hughes Aircraft

Hughes Aircraft Company was a major aerospace and defense company founded by Howard Hughes. The group was based near Ballona Creek, in Culver City, California....
.

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
Cylinder (geometry)

A cylinder is one of the most curvilinear basic geometric shapes: the surface formed by the points at a fixed distance from a given straight line, the axis of the cylinder....
 in shape, roughly long. 980 watt
WATT

WATT is a radio station broadcasting a News radio-Talk radio-Sports radio format. Licensed to Cadillac, Michigan, it first began broadcasting in 1945....
s of electrical power were available from solar panel
Photovoltaic module

In the field of photovoltaics, a photovoltaic module or photovoltaic panel is a packaged interconnected assembly of photovoltaic cells, also known as solar cells....
s and batteries
Battery (electricity)

In electronics, a battery or voltaic cell is a combination of one or more electrochemical cell Galvanic cells which store chemical energy that can be converted into electric potential energy, creating electricity....
. The SDS-1 had a mass of 1385 pound
Pound (mass)

The pound or pound-mass is a Units of measurement of massused in the Imperial unit, United States customary units and other systems of measurement....
s (630 kilogram
Kilogram

The kilogram or kilogrammeThe spelling kilogram is used by the International Committee for Weights and Measures and the U.S....
s) and was launched on Titan-3B
Titan (rocket family)

Titan was a family of United States expendable launch system rockets used between 1959 and 2005. A total of 368 rockets of this family were launched....
 rockets. The SDS-1 satellites had similar orbits to the Air Force's Jumpseat
Jumpseat (satellite)

Jumpseat, also known as AFP-711 is reportedly a code name for a class of SIGINT reconnaissance satellites operated by the National Reconnaissance Office for the United States Air Force in the 1970s and 1980s....
 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
K band

NATO K bandThe NATO K band is defined as a frequency band between 20 and 40 GHz ....
 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
Space Shuttle program

NASA's Space Shuttle, officially called Space Transportation System , is the United States government's current Human spaceflight launch vehicle....
 has been used to launch several satellites, possibly on missions STS-28
STS-28

STS-28 was the third shuttle mission dedicated to United States Department of Defense, and first flight of Space Shuttle Columbia since mission STS-61-C....
, STS-38
STS-38

STS-38 was a space shuttle mission by NASA using the Space Shuttle Atlantis. It was the 37th shuttle mission, and carried a classified information in the United States payload for the U.S....
, and STS-53
STS-53

STS-53 was a Space Shuttle Space Shuttle Discovery mission in support of the United States Department of Defense. The mission was launched on December 2, 1992 from Kennedy Space Center, Florida....
. 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
Cape Canaveral

Cape Canaveral, from the Spanish language Cabo Ca?averal, is a headlands and bays in Brevard County, Florida, United States, near the center of that state's Atlantic Ocean coast 45 minutes East of Orlando by car....
 on August 31, 2004 by an Atlas 2AS rocket.

Launches


SDS-1

  • SDS F-1 launched 1976-06-02 (OPS-7837)
  • SDS F-2 launched 1976-08-06 (OPS-7940)
  • SDS F-3 launched 1978-08-05 (OPS-7310)
  • SDS F-4 launched 1981-04-24 (OPS-7225)
  • SDS F-5A launched 1984-08-28 (USA-4)
  • USA-9 launched 1985-02-08 (USA-9)
  • SDS F-6 launched 1987-02-12 (USA-21)


SDS-2

  • USA-40 launched 1989-08-08 on STS-28
    STS-28

    STS-28 was the third shuttle mission dedicated to United States Department of Defense, and first flight of Space Shuttle Columbia since mission STS-61-C....
      (USA-40)
  • USA-67 launched 1990-11-15 on STS-38
    STS-38

    STS-38 was a space shuttle mission by NASA using the Space Shuttle Atlantis. It was the 37th shuttle mission, and carried a classified information in the United States payload for the U.S....
     )(USA-67)(Some sources identify USA-67 as a Magnum
    Magnum (satellite)

    Magnum is reportedly a code name for a class of SIGINT reconnaissance satellite operated by the National Reconnaissance Office for the United States Central Intelligence Agency....
     SIGINT
    SIGINT

    Signals intelligence is list of intelligence gathering disciplines by interception of signals, whether between people or between machines , or mixtures of the two....
     satellite)
  • USA-89 launched 1992-12-02 on STS-53
    STS-53

    STS-53 was a Space Shuttle Space Shuttle Discovery mission in support of the United States Department of Defense. The mission was launched on December 2, 1992 from Kennedy Space Center, Florida....
      (USA-89)
  • USA-125 launched by Titan IV
    Titan IV

    The Titan IV family of space boosters were used by the U.S. Air Force. They were rocket launch from Cape Canaveral Air Force Station, Florida, and Vandenberg Air Force Base, California....
     1996-07-03 (USA-125)


SDS-3

  • USA-137 Capricorn launched by Atlas IIA
    Atlas II

    Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. Atlas II was the last Atlas to use a three engine, "stage-and-a-half" design: two of its three engines were jettisoned during ascent, but its fuel tanks and other structural elements were retained....
     1998-01-29
  • USA-155 Great Bear launched by Atlas IIAS
    Atlas II

    Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. Atlas II was the last Atlas to use a three engine, "stage-and-a-half" design: two of its three engines were jettisoned during ascent, but its fuel tanks and other structural elements were retained....
     2000-12-06
  • USA-162 Aquilla launched by Atlas IIAS
    Atlas II

    Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. Atlas II was the last Atlas to use a three engine, "stage-and-a-half" design: two of its three engines were jettisoned during ascent, but its fuel tanks and other structural elements were retained....
     2001-10-11
  • USA-179 Nemesis launched by Atlas IIAS
    Atlas II

    Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. Atlas II was the last Atlas to use a three engine, "stage-and-a-half" design: two of its three engines were jettisoned during ascent, but its fuel tanks and other structural elements were retained....
     2004-08-31
  • USA-198 Scorpius launched by Atlas V 401
    Atlas V

    The Atlas V rocket is an expendable launch vehicle formerly built by Lockheed Martin and now built by the Lockheed Martin-Boeing joint venture United Launch Alliance....
     2007-12-10