TheDefense Satellite Communications System(DSCS)[1]is aUnited States Space Forcesatellite constellation that provides the United States with military communications to support globally distributed military users. Beginning in 2007, DSCS began being replaced by theWideband Global SATCOMsystem. A total of 14 DSCS-III satellites were launched between the early 1980s and 2003. Two satellites were launched aboard theSpace ShuttleAtlantisin 1985 during theSTS-51-Jflight. As of 14 September 2021, six DSCS-III satellites were still operational.[2]DSCS operations are currently run by the4th Space Operations Squadronout ofSchriever Space Force Base.
Background
editDSCS 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" ofmilitarysatellite communications.All DSCS III satellites have exceeded their 10-year design life. TheNational Science Foundationuse the DSCS satellites to provide additional bandwidth toAmundsen–Scott South Pole StationandMcMurdo StationonRoss Islandon the continent ofAntarctica.[3]
IDCSP
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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. TheInitial 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 satelliteplaced 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
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DSCS II, developed under Program 777[6]provided securevoiceanddata transmissionfor theUnited States Armed Forces.The program was managed by the Defense Communications Agency (DCA), now theDefense Information Systems Agency.
The space vehicles were spin stabilized with a de-spun antenna platform. The body was mounted withsolar cells,which produced 535watts.ThreeNiCd batteriesprovided electrical power and it was supported by ahydrazinepropulsion subsystem.
The communications payload included two 20-wattX bandchannels. Thetransponderswere supported by steerable narrow beamantennasand drive mechanism for communications privacy.
The first DSCS II launch was in 1971.[7]
DSCS III
editOn 12 December 1975,research and developmentcontracts were awarded toGeneral ElectricandHughes 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]
DSCS III Spacecraft
edit| 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] |
Image gallery
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DSCS-2 diagram -
DSCS-3 diagram
See also
editReferences
edit- ^Burroughs, William E. (1986).Deep Black.New York: Berkley Publishing Group. pp.187.ISBN0-425-10879-1.
- ^"DSCS III Constellation".Air Force Fact Sheet.Archivedfrom the original on 27 April 2017.Retrieved26 April2017.
- ^"DSCS III use for Antarctica".Amundsen-Scott South Pole Station.Archivedfrom the original on 27 April 2017.Retrieved26 April2017.
- ^abMartin, Donald H. (1986).Communication Satellites 1958-1988.El Segundo: Aerospace Corp. p. 285.
- ^McDowell, Jonathan."Satellite Catalog".Jonathon's Space Report.Retrieved27 April2021.
- ^Martin, Donald H. (2000).Communication Satellites.AIAA.ISBN9781884989094.
- ^"DSCS II".Encyclopedia Astronautica.Archived fromthe originalon 26 June 2017.Retrieved27 April2017.
- ^Fiscal year 1977 authorization for military procurement,pt. 6, p. 3769.
- ^"DSCS III".Air Force Fact Sheet.Archivedfrom the original on 27 April 2017.Retrieved26 April2017.
- ^abcdefghij"Defense Satellite Communications System".United States Air Force.November 2015. Archived fromthe originalon 7 January 2023.Retrieved7 January2023.
- ^Gibson, Hillary (14 December 2022)."SpOC officially retires DSCS satellite".Space Operations Command.United States Space Force.Retrieved2 January2023.
External links
edit- Lockheed Martin's Page on DSCS
- Federation of American Scientists - DSCS 3
- U.S. Air Force MILSATCOM - DSCS
- NASA JPL - DSCS
- Air Force - DSCS IIIArchived25 October 2016 at theWayback Machine
- NASA's National Space Science Data Center (NSSDC) - Master Catalog - Spacecraft Query
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