The Defense Satellite Communications System (DSCS) is a

United States Space Force The United States Space Force (USSF) is the space service branch of the U.S. Armed Forces, one of the eight U.S. uniformed services, and the world's only independent space force. Along with its sister branch, the U.S. Air Force, the Space ...

satellite constellation that provides the United States with military communications to support globally distributed military users. Beginning in 2007, DSCS is being replaced by the

Wideband Global SATCOM The Wideband Global SATCOM system (WGS) is a high capacity United States Space Force satellite communications system planned for use in partnership by the United States Department of Defense (DoD), Canadian Department of National Defence (DND) ...

system. A total of 14 DSCS-III satellites were launched between the early 1980s and 2003. Two satellites were launched aboard the

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program ...

''Atlantis'' in 1985 during the

STS-51-J STS-51-J was the 21st NASA Space Shuttle mission and the first flight of Space Shuttle ''Atlantis''. It launched from Kennedy Space Center, Florida, on October 3, 1985, carrying a payload for the U.S. Department of Defense (DoD), and landed a ...

flight. As of 14 September 2021, six DSCS-III satellites were still operational. DSCS operations are currently run by the

4th Space Operations Squadron The United States Space Force's 4th Space Operations Squadron is a satellite operations unit located at Schriever Space Force Base, Colorado. 4 SOPS is part of Space Delta 8 and responsible for command and control of the Milstar/Advanced E ...

out of

Schriever Space Force Base Schriever Space Force Base, previously Schriever Air Force Base, Falcon Air Force Base, and Falcon Air Force Station, is a base of the United States Space Force located approximately east of Peterson Space Force Base near Colorado Springs in ...

Background

DSCS went through three major phases — IDCSP (Interim Defense Communication Satellite Program), DSCS-II, and DSCS-III. Since the first launch, DSCS has been the "workhorse" of

military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...

satellite communications A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. ...

. All DSCS III satellites have exceeded their 10-year design life. The

National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National ...

use the DSCS satellites to provide additional bandwidth to Amundsen–Scott South Pole Station and McMurdo Station on Ross Island on the continent of

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

IDCSP

In April 1960, the Advanced Research Projects Agency (ARPA) began work on the Advent program, which was intended to deliver a military communication satellite. The design concept proved too advanced for the technology of the time, and the program was cancelled in May 1962. The

Initial Defense Communications Satellite Program The Initial Defense Communications Satellite Program or IDCSP was the first United States Department of Defense communications satellite constellation and the first stage of the Defense Communications Satellite Program (DCSP). Launched in five ...

(IDCSP) was one of two recommended follow up approaches to deliver a working satellite. Philco (now Ford Aerospace) was contracted for the work. The IDCSP delivered a simple,

spin-stabilized satellite Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle/satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, e ...

placed into a sub-synchronous orbit that did not require station-keeping or active altitude control. The capacity was approximately 1 Mbit/s digital data. The first launch of 7 satellites was conducted in June 1966. The system was declared operational with the 1968 launch and renamed to Initial Defense Satellite Communication System (IDSCS). A total of 34 IDSCS satellites were built, with 8 lost in a launch failure in August 1966.

DSCS II

DSCS II, developed under Program 777 provided secure

voice The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound producti ...

and

data transmission Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal transmitted over a point-to-point o ...

for the

United States Armed Forces The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is ...

. The program was managed by the Defense Communications Agency (DCA), now the

Defense Information Systems Agency The Defense Information Systems Agency (DISA), known as the Defense Communications Agency (DCA) until 1991, is a United States Department of Defense (DoD) combat support agency composed of military, federal civilians, and contractors. DISA pro ...

. The space vehicles were spin stabilized with a de-spun antenna platform. The body was mounted with

solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

s, which produced 535

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

s. Three NiCd batteries provided electrical power and it was supported by a hydrazine propulsion subsystem. The communications payload included two 20-watt X band channels. The

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

s were supported by steerable narrow beam antennas and drive mechanism for communications privacy. The first DSCS II launch was in 1971.

DSCS III

On 12 December 1975 research and development contracts were awarded to

General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable en ...

and Hughes Aircraft Company to begin DSCS III design studies, with the first Block 1 launch on 30 October 1982. DSCS III satellites support globally distributed Department of Defense (DoD) and national security users. The final 4 of 14 satellites received Service Life Enhancement Program (SLEP) modifications. These changes provided substantial capacity improvements through higher power amplifiers, more sensitive receivers, and additional antenna connectivity options. The DSCS communications payload includes six independent Super High Frequency (SHF) transponder channels that cover a 500 MHz bandwidth. Three receive and five transmit antennas provide selectable options for Earth coverage, area coverage and/or spot beam coverage. A special purpose single-channel transponder is also on board.

DSCS III Spacecraft

Image gallery

File:DSCS 2 diagram.PNG, DSCS-2 diagram File:DSCS 3 diagram.PNG, DSCS-3 diagram

References

External links

Lockheed Martin's Page on DSCSU.S. Air Force MILSATCOM - DSCSAir Force - DSCS IIINASA's National Space Science Data Center (NSSDC) - Master Catalog - Spacecraft Query
{{Use American English, date=January 2014 6 Communications satellite constellations Military communications of the United States Military satellites of the United States Spacecraft launched by Atlas rockets Spacecraft launched by Delta IV rockets Spacecraft launched by the Space Shuttle Spacecraft launched by Titan rockets Equipment of the United States Space Force Military equipment introduced in the 1960s ja:アメリカ軍の衛星通信#DSCS