The Defense Satellite Communications System (DSCS) [1] is a United States Space Force 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 Atlantis in 1985 during the STS-51-J flight. As of 14 September 2021, six DSCS-III satellites were still operational. [2] DSCS operations are currently run by the 4th Space Operations Squadron out of Schriever Space Force Base.
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 satellite communications. All DSCS III satellites have exceeded their 10-year design life. The National Science Foundation 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. [3]
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 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). [4]
A total of 34 IDSCS satellites were built, with 8 lost in a launch failure in August 1966. [5]
DSCS II, developed under Program 777 [6] provided secure voice and data transmission for the United States Armed Forces. The program was managed by the Defense Communications Agency (DCA), now the Defense Information Systems Agency.
The space vehicles were spin stabilized with a de-spun antenna platform. The body was mounted with solar cells, which produced 535 watts. 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 transponders were supported by steerable narrow beam antennas and drive mechanism for communications privacy.
The first DSCS II launch was in 1971. [7]
On 12 December 1975, research and development contracts were awarded to General Electric and Hughes Aircraft Company [8] to begin DSCS III design studies, with the first Block 1 launch on 30 October 1982. [4]
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. [9]
Spacecraft Name | Other Designation | Launch date/time (UTC) | NSSDCA/COSPAR ID | Rocket | Status/Remarks |
---|---|---|---|---|---|
DSCS III-01 | DSCS III-A1 | 1982-10-30, 04:05:00 | 1982-106B | Titan 34D | Decommissioned/Launched with DSCS II-16 |
USA-11 | DSCS III-B4 | 1985-10-03, 15:15:30 | 1985-092B | Space Shuttle Atlantis | Decommissioned [10] |
USA-12 | DSCS III-B5 | 1985-10-03, 15:15:30 | 1985-092C | Space Shuttle Atlantis | Decommissioned [10] |
USA-43 | DSCS III-06 or DSCS III-A2 | 1989-09-04, 05:54:00 | 1989-069A | Titan 34D | Decommissioned [10] |
USA-44 | DSCS III-07 | 1989-09-04, 05:54:00 | 1989-069B | Titan 34D | |
USA-78 | DSCS III-08 | 1992-02-10, 00:41:00 | 1992-006A | Atlas II | Decommissioned [10] |
USA-82 | DSCS III-09 | 1992-07-02, 21:54:00 | 1992-037A | Atlas II | Decommissioned [10] |
USA-93 | DSCS III-10 | 1993-07-19, 22:04:00 | 1993-046A | Atlas II | Decommissioned [10] |
USA-97 | DSCS III-11 | 1993-11-28, 23:40:00 | 1993-074A | Atlas II | |
USA-113 | DSCS III-B7 | 1995-07-31, 23:30:00 | 1995-038A | Atlas IIA | Decommissioned on 9 December 2022. [11] |
USA-134 | DSCS III-B13 | 1997-10-25, 00:46:00 | 1997-065A | Atlas IIA | Operational [10] |
USA-148 | DSCS III-B11 | 2000-01-25, 01:03:00 UTC | 2000-001A | Atlas IIA | Operational [10] |
USA-167 | DSCS III-A3 | 2003-03-11, 00:59:00 UTC | 2003-008A | Delta IV | Operational [10] |
USA-170 | DSCS III-B6 | 2003-08-29, 23:13:00 UTC | 2003-040A | Delta IV | Operational [10] |
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. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit 22,236 miles (35,785 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently.
Syncom started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by the Space and Communications division of Hughes Aircraft Company. Syncom 2, launched in 1963, was the world's first geosynchronous communications satellite. Syncom 3, launched in 1964, was the world's first geostationary satellite.
Skynet is a family of military communications satellites, now operated by Babcock International on behalf of the United Kingdom's Ministry of Defence (MoD). They provide strategic and tactical communication services to the branches of the British Armed Forces, the British intelligence agencies, some UK government departments and agencies, and to allied governments. Since 2015 when Skynet coverage was extended eastward, and in conjunction with an Anik G1 satellite module over America, Skynet offers near global coverage.
The Indian National Satellite System or INSAT, is a series of multipurpose geostationary satellites launched by the Indian Space Research Organisation (ISRO) to satisfy telecommunications, broadcasting, meteorology, and search and rescue operations. Commissioned in 1983, INSAT is the largest domestic communication system in the Indo-Pacific Region. It is a joint venture of the Department of Space, Department of Telecommunications, India Meteorological Department, All India Radio and Doordarshan. The overall coordination and management of INSAT system rests with the Secretary-level INSAT Coordination Committee.
A military satellite is an artificial satellite used for a military purpose. The most common missions are intelligence gathering, navigation and military communications.
Milstar is a constellation of military communications satellites in geosynchronous orbit, which are operated by the United States Space Force, and provide secure and jam-resistant worldwide communications to meet the requirements of the Armed Forces of the United States. Six spacecraft were launched between 1994 and 2003, of which only five were operational after launch; the third launch failed, both damaging the satellite and leaving it in an unusable orbit.
GPS Block III consists of the first ten GPS III satellites, which will be used to keep the Navstar Global Positioning System operational. Lockheed Martin designed, developed and manufactured the GPS III Non-Flight Satellite Testbed (GNST) and all ten Block III satellites. The first satellite in the series was launched in December 2018.
Space Systems Command (SSC) is the United States Space Force's space development, acquisition, launch, and logistics field command. It is headquartered at Los Angeles Air Force Base, California, and manages the United States' space launch ranges.
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) and the Australian Department of Defence. The system is composed of the Space Segment satellites, the Terminal Segment users and the Control Segment operators.
Advanced Extremely High Frequency (AEHF) is a constellation of communications satellites operated by the United States Space Force. They are used to relay secure communications for the United States Armed Forces, the British Armed Forces, the Canadian Armed Forces, the Netherlands Armed Forces and the Australian Defence Force. The system consists of six satellites in geostationary orbits. The final satellite was launched on 26 March 2020. AEHF is backward compatible with, and replaces, the older Milstar system and will operate at 44 GHz uplink and 20 GHz downlink. The AEHF system is a joint service communications system that provides survivable, global, secure, protected, and jam-resistant communications for high-priority military ground, sea and air assets.
USA-195, or Wideband Global SATCOM 1 (WGS-1) is a United States military communications satellite operated by the United States Air Force as part of the Wideband Global SATCOM programme. Launched in 2007, it was the first WGS satellite to reach orbit. It is stationed at a longitude of 174.8° East.
A hosted payload is a module attached to a commercial satellite with communications circuitry that operates independently of the main spacecraft but which shares the satellite's power supply and transponders. The concept has been also been referred to as "piggybacking" or "hitchhiking."
USA-204, or Wideband Global SATCOM 2 (WGS-2) is a United States military communications satellite which is operated by the United States Air Force as part of the Wideband Global SATCOM programme. Launched in 2009, it was the second WGS satellite to reach orbit, and operates in geostationary orbit at a longitude of 60° East.
X band or SHF Satellite Communication is widely used by military forces for beyond line of sight communications. X band is used because it provides a compromise between the characteristics of different frequency bands which is particularly suited to the needs of military users. The characteristics include interference and rain resilience, terminal size, data rates, remote coverage and whether it is reserved for governmental use.
GSAT-7A is an advanced military communications satellite meant primarily for the Indian Air Force with Indian Army using 30% of capacity.
While the United States Space Force gained its independence on 20 December 2019, the history of the United States Space Force can be traced back to the beginnings of the military space program following the conclusion of the Second World War in 1945. Early military space development was begun within the United States Army Air Forces by General Henry H. Arnold, who identified space as a crucial military arena decades before the first spaceflight. Gaining its independence from the Army on 18 September 1947, the United States Air Force began development of military space and ballistic missile programs, while also competing with the United States Army and United States Navy for the space mission.
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 groups by Titan IIIC launch vehicles to near equatorial, subsynchronous orbits between 1966 and 1968, they were intended to be experimental testbeds. They were so successful that, by the time of the launch of the last set of eight satellites, the IDCSP was deemed operational and renamed Initial Defense Satellite Communications System or IDSCS. This system allowed real-time collection of battlefield intelligence during the Vietnam War. A total of 35 IDCSP satellites were launched, 27 successfully.
USA-263, or Wideband Global SATCOM 7 (WGS-7) is a United States military communications satellite operated by the United States Air Force as part of the Wideband Global SATCOM programme. Launched in 2015, it was the seventh WGS satellite to reach orbit. It is stationed at a longitude of 135° West, in geostationary orbit. WGS-7 was procured by the United States Air Force.
USA-275, or Wideband Global SATCOM 9 (WGS-9) is a United States military communications satellite operated by the United States Air Force as part of the Wideband Global SATCOM programme. Launched in 2017, it was the ninth WGS satellite to reach orbit. It is stationed at a longitude of 135° West, in geostationary orbit. WGS-9 was procured by the United States Air Force.
Wideband Global SATCOM 11+, is a United States military communications satellite to be operated by the United States Space Force as part of the Wideband Global SATCOM Program. Scheduled for 2024, it is the eleventh WGS satellite and is expected to be in geostationary orbit. WGS 11+ was acquired by the United States Air Force.
6