The Defense Satellite Communications System (DSCS) is a

United States Space Force The United States Space Force (USSF) is the space force branch of the United States Department of Defense. It is one of the six United States Armed Forces, armed forces of the United States and one of the eight uniformed services of the Unite ...

satellite constellation that provides the United States with military communications to support globally distributed military users. Beginning in 2007, DSCS began being replaced by the Wideband Global SATCOM 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 launch system, 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. ...

''Atlantis'' in 1985 during the STS-51-J 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 (4 SOPS) 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/Adv ...

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, Col ...

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. Militaries are typically authorized and maintained by a sovereign state, with their members identifiable by a d ...

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 U.S. National Science Foundation (NSF) is an Independent agencies of the United States government#Examples of independent agencies, independent agency of the Federal government of the United States, United States federal government that su ...

use the DSCS satellites to provide additional bandwidth to

Amundsen–Scott South Pole Station The Amundsen–Scott South Pole Station is a science and technology in the United States, United States scientific research station at the South Pole of the Earth. It is the List of extreme points of the United States, southernmost point under ...

and

McMurdo Station McMurdo Station is an American Antarctic research station on the southern tip of Ross Island. It is operated by the United States through the United States Antarctic Program (USAP), a branch of the National Science Foundation. The station is ...

Ross Island Ross Island is an island in Antarctica lying on the east side of McMurdo Sound and extending from Cape Bird in the north to Cape Armitage in the south, and a similar distance from Cape Royds in the west to Cape Crozier in the east. The isl ...

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 (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

IDCSP

In April 1960, the Advanced Research Projects Agency (ARPA) initiated the Advent program, aiming to deliver a military communication satellite. However, the design concept surpassed the technological capabilities of the time, leading to the cancellation of the program in May 1962. The Initial Defense Communications Satellite Program (IDCSP) was proposed as 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 or satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, ...

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, comprising 7 satellites, took place 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 produ ...

and

data transmission Data communication, including data transmission and data reception, is the transfer of data, signal transmission, transmitted and received over a Point-to-point (telecommunications), point-to-point or point-to-multipoint communication chann ...

for the

United States Armed Forces The United States Armed Forces are the Military, military forces of the United States. U.S. United States Code, federal law names six armed forces: the United States Army, Army, United States Marine Corps, Marine Corps, United States Navy, Na ...

. 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. It is composed of military, federal civilians, and contractors. D ...

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

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s, which produced 535

watt The watt (symbol: W) is the unit of Power (physics), 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 quantification (science), quantify the rate of Work ...

s. Three NiCd batteries provided electrical power and it was supported by a

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...

propulsion subsystem. The communications payload included two 20-watt

X band The X band is the designation for a band of frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is set at approximately 7.0–11.2&nbs ...

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 Research and development (R&D or R+D), known in some countries as OKB, experiment and design, is the set of innovative activities undertaken by corporations or governments in developing new services or products. R&D constitutes the first stage ...

contracts were awarded to

General Electric General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...

and

Hughes Aircraft Company The Hughes Aircraft Company was a major American aerospace and defense contractor founded on February 14, 1934 by Howard Hughes in Glendale, California, as a division of the Hughes Tool Company. The company produced the Hughes H-4 Hercules air ...

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 III

NASA'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