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 purpose of telecommunications...

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

In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

, going from about 300 kilometers at perigee

Perigee

Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...

 to roughly 39,000 km at apogee in order to allow communications with polar

Geographical pole

A geographical pole is either of the two points—the north pole and the south pole—on the surface of a rotating planet where the axis of rotation 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. In addition, two geostationary satellites appear to be part of the system. The SDS satellites were constructed by Hughes Aircraft

Hughes Aircraft

Hughes Aircraft Company was a major American aerospace and defense contractor founded in 1932 by Howard Hughes in Culver City, California as a division of Hughes Tool Company...

.

The primary purpose of the SDS satellites is to relay imagery from low-flying reconnaissance satellites, notably the Keyhole

Key Hole

Key Hole is the designation for a series of American optical reconnaissance satellites:* KH-1 Corona* KH-2 Corona* KH-3 Corona* KH-4 Corona* KH-5 Argon* KH-6 Lanyard* KH-7 Gambit* KH-8 Gambit 3* KH-9 Hexagon/Big Bird...

 optic reconnaissance and Lacrosse/Onyx

Lacrosse (satellite)

For the 2009 Lunar Impactor Mission designed to crash into the moon, see LCROSS.Lacrosse and Onyx are the code names for the United States' National Reconnaissance Office terrestrial radar imaging reconnaissance satellite. While not officially confirmed by the NRO or anybody in the U.S...

 radar 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 basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 in shape, roughly 25 feet (7.6 m) long. 980 watt

Watt

The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

s of electrical power were available from solar panel

Photovoltaic module

A solar panel is a packaged, connected assembly of solar cells, also known as photovoltaic cells...

s and batteries

Battery (electricity)

An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

. The SDS-1 had a mass of 1385 pound

Pound (mass)

The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

s (630 kilogram

Kilogram

The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

s) and was launched on Titan-3B

Titan (rocket family)

Titan was a family of U.S. expendable rockets used between 1959 and 2005. A total of 368 rockets of this family were launched, including all the Project Gemini manned flights of the mid-1960s...

 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

K band designates certain portions of the electromagnetic spectrum, in either the microwave domain or in the infrared domain. The microwave K bands are used primarily for radar and satellite communications while the infrared K band is used for astronomical observations.-NATO K band:The NATO 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

Space Shuttle program

NASA's Space Shuttle program, officially called Space Transportation System , was the United States government's manned launch vehicle program from 1981 to 2011...

 has been used to launch several satellites, possibly on missions STS-28

STS-28

STS-28 was the 30th NASA Space Shuttle mission, the fourth shuttle mission dedicated to United States Department of Defense purposes, and the eighth flight of Space Shuttle Columbia. The mission launched on 8 August 1989, lasted just over 5 days, and traveled 2.1 million miles during 81 orbits...

, STS-38

STS-38

-Mission parameters:*Mass:**Payload: Magnum ELINT satellite ~ **Booster: IUS upper stage ~ **Total: ~ *Perigee: *Apogee: *Inclination: 28.5°*Period: 87.5 min-Preparations and Launch:...

, and STS-53

STS-53

-Mission parameters:*Mass:**Orbiter landing with payload: **Payload: *Perigee: *Apogee: *Inclination: 57.0°*Period: 92.0 min-Mission highlights:...

. 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 Cabo Cañaveral, is a headland in Brevard County, Florida, United States, near the center of the state's Atlantic coast. Known as Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated from it by the Banana River.It is part of a region known as the...

 on August 31, 2004 by an Atlas 2AS rocket.

Satellites

Name	ID International Designator The International Designator, also known as COSPAR designation, and in the United States as NSSDC ID, is an international naming convention for satellites...	Launch date	Launch vehicle	Launch site	NROL designation	Perigee Perigee Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...	Apogee	Inclination	Remarks
First generation
	1976-050A	1976-06-02	Titan III(34)B	VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....  SLC-4W Vandenberg AFB Space Launch Complex 4 Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...	N/A
OPS 7940	1976-080A	1976-08-06	Titan III(34)B	VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....  SLC-4W Vandenberg AFB Space Launch Complex 4 Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...
OPS 7310	1978-075A	1978-08-05	Titan III(34)B	VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....  SLC-4W Vandenberg AFB Space Launch Complex 4 Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...
OPS 5805	1980-100A	1980-12-13	Titan III(34)B	VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....  SLC-4W Vandenberg AFB Space Launch Complex 4 Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...
USA-4	1978-091A	1984-08-28	Titan III(34)B	VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....  SLC-4W Vandenberg AFB Space Launch Complex 4 Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...
USA-9	1985-014A	1985-02-08	Titan III(34)B	VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....  SLC-4W Vandenberg AFB Space Launch Complex 4 Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...
USA-21	1987-015A	1987-02-15	Titan III(34)B	VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....  SLC-4W Vandenberg AFB Space Launch Complex 4 Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...
Second generation
USA-40	1989-061B	1989-06-02	STS-28 STS-28 STS-28 was the 30th NASA Space Shuttle mission, the fourth shuttle mission dedicated to United States Department of Defense purposes, and the eighth flight of Space Shuttle Columbia. The mission launched on 8 August 1989, lasted just over 5 days, and traveled 2.1 million miles during 81 orbits... /Orbus-21S	KSC Kennedy Space Center The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...  LC-39B Kennedy Space Center Launch Complex 39 Launch Complex 39 is a rocket launch site at the John F. Kennedy Space Center on Merritt Island in Florida, USA. The site and its collection of facilities were originally built for the Apollo program, and later modified to support Space Shuttle operations. NASA began modifying LC-39 in 2007 to...	N/A
USA-67	1990-097B	1990-11-15	STS-38 STS-38 -Mission parameters:*Mass:**Payload: Magnum ELINT satellite ~ **Booster: IUS upper stage ~ **Total: ~ *Perigee: *Apogee: *Inclination: 28.5°*Period: 87.5 min-Preparations and Launch:... /Orbus-21S	KSC Kennedy Space Center The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...  LC-39A Kennedy Space Center Launch Complex 39 Launch Complex 39 is a rocket launch site at the John F. Kennedy Space Center on Merritt Island in Florida, USA. The site and its collection of facilities were originally built for the Apollo program, and later modified to support Space Shuttle operations. NASA began modifying LC-39 in 2007 to...					Geosynchronous satellite, deployed along with Prowler and initially misidentified as a Magnum Magnum (satellite) Magnum is the code name for a class of SIGINT spy satellites reportedly operated by the National Reconnaissance Office for the United States Central Intelligence Agency...  SIGINT spacecraft
USA-89	1992-086B	1992-12-02	STS-53 STS-53 -Mission parameters:*Mass:**Orbiter landing with payload: **Payload: *Perigee: *Apogee: *Inclination: 57.0°*Period: 92.0 min-Mission highlights:... /Orbus-21S	KSC Kennedy Space Center The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...  LC-39A Kennedy Space Center Launch Complex 39 Launch Complex 39 is a rocket launch site at the John F. Kennedy Space Center on Merritt Island in Florida, USA. The site and its collection of facilities were originally built for the Apollo program, and later modified to support Space Shuttle operations. NASA began modifying LC-39 in 2007 to...
USA-125	1996-038B	1996-07-03	Titan IV(405)A Titan IV The Titan IV family of space boosters were used by the U.S. Air Force. They were launched from Cape Canaveral Air Force Station, Florida, and Vandenberg Air Force Base, California. At the time of its introduction, the Titan IV was the "largest unmanned space booster used by the Air Force."The...	CCAFS Cape Canaveral Air Force Station Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...  LC-40
Third generation
USA-137	1998-005A	1998-01-29	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...	CCAFS Cape Canaveral Air Force Station Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...  SLC-36A	NROL-5				Capricorn
USA-155	2000-080A	2000-12-06	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...	CCAFS Cape Canaveral Air Force Station Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...  SLC-36A	NROL-10				Great Bear, geosynchronous satellite
USA-162	2001-046A	2001-10-11	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...	CCAFS Cape Canaveral Air Force Station Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...  SLC-36B	NROL-12				Aquilla, geosynchronous satellite
USA-179	2004-034A	2004-08-31	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...		NROL-1				Nemesis, final Atlas II launch
USA-198	2007-060A	2007-12-10	Atlas V Atlas V Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...  401	CCAFS Cape Canaveral Air Force Station Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...  SLC-41	NROL-24				Scorpius
USA-227 USA-227 USA-227, known before launch as NRO Launch 27 , is an American communications satellite which was launched in 2011. It is operated by the United States National Reconnaissance Office....	2011-011A	2011-03-11	Delta IV-M+(4,2)	CCAFS Cape Canaveral Air Force Station Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...  SLC-37B	NROL-27				Gryphon, geosynchronous satellite