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Defense Satellite Communications System

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Illustration of the DSCS III satellite

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.

Background

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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

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Artist's rendering of a Transtage deploying IDSCP satellites
Artist's rendering of a Transtage deploying IDSCP satellites
Main article: Initial Defense Communications Satellite Program

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

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Illustration of a DSCS II satellite
Overview of DSCS II, circa 1977

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]

DSCS III

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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]

DSCS III Spacecraft

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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]
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  • DSCS-2 diagram
    DSCS-2 diagram
  • DSCS-3 diagram
    DSCS-3 diagram

See also

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References

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  1. ^ Burroughs, William E. (1986). Deep Black. New York: Berkley Publishing Group. pp. 187. ISBN 0-425-10879-1.
  2. ^ "DSCS III Constellation". Air Force Fact Sheet. Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  3. ^ "DSCS III use for Antarctica". Amundsen-Scott South Pole Station. Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  4. ^ a b Martin, Donald H. (1986). Communication Satellites 1958-1988. El Segundo: Aerospace Corp. p. 285.
  5. ^ McDowell, Jonathan. "Satellite Catalog". Jonathon's Space Report. Retrieved 27 April 2021.
  6. ^ Martin, Donald H. (2000). Communication Satellites. AIAA. ISBN 9781884989094.
  7. ^ "DSCS II". Encyclopedia Astronautica. Archived from the original on 26 June 2017. Retrieved 27 April 2017.
  8. ^ Fiscal year 1977 authorization for military procurement, pt. 6, p. 3769.
  9. ^ "DSCS III". Air Force Fact Sheet. Archived from the original on 27 April 2017. Retrieved 26 April 2017.
  10. ^ a b c d e f g h i j "Defense Satellite Communications System". United States Air Force. November 2015. Archived from the original on 7 January 2023. Retrieved 7 January 2023.
  11. ^ Gibson, Hillary (14 December 2022). "SpOC officially retires DSCS satellite". Space Operations Command. United States Space Force. Retrieved 2 January 2023.
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