Defense Satellite Communications System






Defense satellite communications project





Illustration of the DSCS III satellite


The Defense Satellite Communications System (DSCS)[1] 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 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 23 November 2015, seven DSCS-III satellites were still operational.[2] DSCS operations are currently run by the 3d Space Operations Squadron out of Schriever Air Force Base.




Contents






  • 1 Background


  • 2 IDCSP


  • 3 DSCS II


  • 4 DSCS III


    • 4.1 DSCS III Spacecraft




  • 5 Image gallery


  • 6 See also


  • 7 References


  • 8 External links





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 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]



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. 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 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.[4]



DSCS II


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Illustration of a DSCS II satellite




File:US DoD DSCS Overview-1977.ogvPlay media

Overview of DSCS II, circa 1977



DSCS II, developed under Program 777[5] 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.[6]



DSCS III


On 12 December 1975 research and development contracts were awarded to General Electric and Hughes Aircraft Company.[7] 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.[8]



DSCS III Spacecraft



























































































































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

USA-12
 DSCS III-B5
 1985-10-03, 15:15:30
1985-092C
Space Shuttle Atlantis

USA-43
 DSCS III-06 or DSCS III-A2
 1989-09-04, 05:54:00
1989-069A
Titan 34D

USA-44
 DSCS III-07
 1989-09-04, 05:54:00
1989-069B
Titan 34D

USA-78
 DSCS III-08
 1993-07-19, 22:04:00
1993-046A
Atlas II

USA-82
 DSCS III-09
 1993-07-19, 22:04:00
1993-046A
Atlas II

USA-93
 DSCS III-10
 1993-07-19, 22:04:00
1993-046A
Atlas II

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

USA-134
 DSCS III-B13
 1997-10-25, 00:46:00
1997-065A
Atlas IIA

USA-148
 DSCS III-B11
 2000-01-25, 01:03:00 UTC
2000-001A
Atlas IIA

USA-167
 DSCS III-A3
 2003-03-11, 00:59:00 UTC
2003-008A
Delta IV

USA-170
 DSCS III-B6
 2003-08-29, 23:13:00 UTC
2003-040A
Delta IV


Image gallery






  • DSCS-2 diagram







  • DSCS-3 diagram






See also


  • Milstar


References





  1. ^ Burroughs, William E. (1986). Deep Black. New York: Berkley Publishing Group. p. 187. ISBN 0-425-10879-1..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output .citation q{quotes:"""""""'""'"}.mw-parser-output .citation .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-maint{display:none;color:#33aa33;margin-left:0.3em}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}


  2. ^ "DSCS III Constellation". Air Force Fact Sheet.


  3. ^ "DSCS III use for Antarctica". Amundsen-Scott South Pole Station.


  4. ^ ab Martin, Donald H. (1986). Communication Satellites 1958-1988. El Segundo: Aerospace Corp. p. 285.


  5. ^ Martin, Donald H. (2000). Communication Satellites. AIAA. ISBN 9781884989094.


  6. ^ "DSCS II". Encyclopedia Astronautica.


  7. ^ Fiscal year 1977 authorization for military procurement, pt. 6, p. 3769.


  8. ^ "DSCS III". Air Force Fact Sheet.




External links



  • Lockheed Martin's Page on DSCS

  • Federation of American Scientists - DSCS 3

  • U.S. Air Force MILSATCOM - DSCS

  • NASA JPL - DSCS

  • Air Force - DSCS III

  • NASA's National Space Science Data Center (NSSDC) - Master Catalog - Spacecraft Query











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