{{Short description|Defense satellite communications project}} {{Use American English|date = March 2019}} {{Use dmy dates|date = March 2019}} [[File:DSCS-3 1.jpg|300px|thumb|Illustration of the DSCS III satellite]] The '''Defense Satellite Communications System''' ('''DSCS''')<ref name=Burroughs>{{cite book |last=Burroughs |first=William E. |year=1986 |title=Deep Black |location=New York |publisher=Berkley Publishing Group |isbn=0-425-10879-1 |pages=[https://archive.org/details/deepblackspacees00burr/page/187 187] |url-access=registration |url=https://archive.org/details/deepblackspacees00burr/page/187 }}</ref> 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]] [[Space Shuttle Atlantis|''Atlantis'']] in 1985 during the [[STS-51-J]] flight. As of 14 September 2021, six DSCS-III satellites were still operational.<ref>{{cite web |url=http://www.af.mil/About-Us/Fact-Sheets/Display/Article/104555/defense-satellite-communications-system/ |title=DSCS III Constellation |work=Air Force Fact Sheet |access-date=26 April 2017 |archive-url=https://web.archive.org/web/20170427103500/http://www.af.mil/About-Us/Fact-Sheets/Display/Article/104555/defense-satellite-communications-system/ |archive-date=27 April 2017 |url-status=dead }}</ref> DSCS operations are currently run by the [[4th Space Operations Squadron]] out of [[Schriever Space Force Base]].
==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|military]] [[Communications satellite|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]].<ref>{{cite web |url=http://www.southpolestation.com/trivia/10s/10s.html#goes |title=DSCS III use for Antarctica |work=Amundsen-Scott South Pole Station |access-date=26 April 2017 |archive-url=https://web.archive.org/web/20170427103507/http://www.southpolestation.com/trivia/10s/10s.html#goes |archive-date=27 April 2017 |url-status=live }}</ref>
==IDCSP== [[File:Idcspdep.jpg|thumb|Artist's rendering of a Transtage deploying IDSCP satellites|alt=Artist's rendering of a Transtage deploying IDSCP satellites]] {{Main|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).<ref name=Martin>{{cite book |last=Martin |first=Donald H. |year=1986|title=Communication Satellites 1958-1988|location=El Segundo |publisher=Aerospace Corp.|pages=285}}</ref>
A total of 34 IDSCS satellites were built, with 8 lost in a launch failure in August 1966.<ref name=cat>{{Cite web|url=https://www.planet4589.org/space/log/satcat.txt|title=Satellite Catalog|last=McDowell|first=Jonathan|publisher=Jonathon's Space Report|access-date=27 April 2021}}</ref>
==DSCS II== {{multiple image |align=right |total_width=450 |image1=DSCS-2 2.jpg |caption1=Illustration of a DSCS II satellite |image2=US DoD DSCS Overview-1977.ogv |caption2=Overview of DSCS II, circa 1977 }}
DSCS II, developed under Program 777<ref>{{Cite book |url=https://books.google.com/books?id=_azf94TByF8C&q=777+DSCS&pg=PA181 |title=Communication Satellites |last=Martin |first=Donald H. |date=2000 |publisher=AIAA |isbn=9781884989094 |language=en}}</ref> provided secure [[circuit switching|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 cell]]s, which produced 535 [[watt]]s. Three [[Nickel–cadmium battery|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 [[transponder]]s were supported by steerable narrow beam [[Antenna (radio)|antenna]]s and drive mechanism for communications privacy.
The first DSCS II launch was in 1971.<ref>{{cite encyclopedia |url=http://www.astronautix.com/d/dscsii.html |title=DSCS II |encyclopedia=Encyclopedia Astronautica |access-date=27 April 2017 |archive-url=https://web.archive.org/web/20170626195308/http://www.astronautix.com/d/dscsii.html |archive-date=26 June 2017 |url-status=dead }}</ref>
==DSCS III== On 12 December 1975, [[research and development]] contracts were awarded to [[General Electric]] and [[Hughes Aircraft Company]]<ref>[https://babel.hathitrust.org/cgi/pt?id=mdp.39015074749436;view=1up;seq=719 Fiscal year 1977 authorization for military procurement], pt. 6, p. 3769.</ref> to begin DSCS III design studies, with the first Block 1 launch on 30 October 1982.<ref name=Martin/>
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.<ref>{{cite web |url=http://www.af.mil/About-Us/Fact-Sheets/Display/Article/104555/defense-satellite-communications-system/ |title=DSCS III |work=Air Force Fact Sheet |access-date=26 April 2017 |archive-url=https://web.archive.org/web/20170427103500/http://www.af.mil/About-Us/Fact-Sheets/Display/Article/104555/defense-satellite-communications-system/ |archive-date=27 April 2017 |url-status=dead }}</ref>
===DSCS III Spacecraft=== {| class="wikitable" |- ! Spacecraft Name ! Other Designation ! Launch date/time (UTC) ! [[International Designator|NSSDCA/COSPAR ID]] ! Rocket ! Status/Remarks |- |DSCS III-01 |DSCS III-A1 |1982-10-30, 04:05:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1982-106B 1982-106B] |[[Titan 34D]] |Decommissioned/Launched with DSCS II-16 |- |[[USA-11]] |DSCS III-B4 |1985-10-03, 15:15:30 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1985-092B 1985-092B] |[[Space Shuttle Atlantis]] |Decommissioned<ref name="af-dscs">{{cite web |url=https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104555/defense-satellite-communications-system/ |title=Defense Satellite Communications System |work=[[United States Air Force]] |date=November 2015 |access-date=7 January 2023 |archive-date=7 January 2023 |archive-url=https://web.archive.org/web/20230107212437/https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104555/defense-satellite-communications-system/ |url-status=dead }}</ref> |- |[[USA-12]] |DSCS III-B5 |1985-10-03, 15:15:30 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1985-092C 1985-092C] |[[Space Shuttle Atlantis]] |Decommissioned<ref name="af-dscs" /> |- |[[USA-43]] |DSCS III-06 or DSCS III-A2 |1989-09-04, 05:54:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1989-069A 1989-069A] |[[Titan 34D]] |Decommissioned<ref name="af-dscs" /> |- |[[USA-44]] |DSCS III-07 |1989-09-04, 05:54:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1989-069B 1989-069B] |[[Titan 34D]] | |- |[[USA-78]] |DSCS III-08 |1992-02-10, 00:41:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1992-006A 1992-006A] |[[Atlas II]] |Decommissioned<ref name="af-dscs" /> |- |[[USA-82]] |DSCS III-09 |1992-07-02, 21:54:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1992-037A 1992-037A] |[[Atlas II]] |Decommissioned<ref name="af-dscs" /> |- |[[USA-93]] |DSCS III-10 |1993-07-19, 22:04:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1993-046A 1993-046A] |[[Atlas II]] |Decommissioned<ref name="af-dscs" /> |- |[[USA-97]] |DSCS III-11 |1993-11-28, 23:40:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1993-074A 1993-074A] |[[Atlas II]] | |- |[[USA-113]] |DSCS III-B7 |1995-07-31, 23:30:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1995-038A 1995-038A] |[[Atlas II|Atlas IIA]] |Decommissioned on 9 December 2022.<ref>{{cite web |last=Gibson |first=Hillary |url=https://www.spoc.spaceforce.mil/News/Article-Display/Article/3245751/spoc-officially-retires-dscs-satellite |title=SpOC officially retires DSCS satellite |work=[[Space Operations Command]] |publisher=[[United States Space Force]] |date=14 December 2022 |access-date=2 January 2023}}</ref> |- |[[USA-134]] |DSCS III-B13 |1997-10-25, 00:46:00 |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1997-065A 1997-065A] |[[Atlas II|Atlas IIA]] |Operational<ref name="af-dscs" /> |- |[[USA-148]] |DSCS III-B11 |2000-01-25, 01:03:00 UTC |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2000-001A 2000-001A] |[[Atlas II|Atlas IIA]] |Operational<ref name="af-dscs" /> |- |[[USA-167]] |DSCS III-A3 |2003-03-11, 00:59:00 UTC |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2003-008A 2003-008A] |[[Delta IV]] |Operational<ref name="af-dscs" /> |- |[[USA-170]] |DSCS III-B6 |2003-08-29, 23:13:00 UTC |[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2003-040A 2003-040A] |[[Delta IV]] |Operational<ref name="af-dscs" /> |- |}
==Image gallery== <gallery> File:DSCS 2 diagram.PNG|DSCS-2 diagram File:DSCS 3 diagram.PNG|DSCS-3 diagram </gallery>
==See also== *[[Milstar]] *[[SpaceX Starshield]]
==References== {{reflist}}
==External links== *[http://www.lockheedmartin.com/us/products/dscs.html Lockheed Martin's Page on DSCS] *[http://www.fas.org/spp/military/program/com/dscs_3.htm Federation of American Scientists - DSCS 3] *[https://www.losangeles.spaceforce.mil/?id=5322 U.S. Air Force MILSATCOM - DSCS] *[https://web.archive.org/web/20070429104831/http://msl.jpl.nasa.gov/Programs/dscs.html NASA JPL - DSCS] *[https://web.archive.org/web/20130917233415/http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104555/defense-satellite-communications-system.aspx Air Force - DSCS III] *[http://nssdc.gsfc.nasa.gov/nmc/SpacecraftQuery.jsp NASA's National Space Science Data Center (NSSDC) - Master Catalog - Spacecraft Query]
{{USAF space vehicles}}
[[Category:Communications satellite constellations]] [[Category:Military communications of the United States]] [[Category:Military satellites of the United States]] [[Category:Spacecraft launched by Atlas rockets]] [[Category:Spacecraft launched by Delta IV rockets]] [[Category:Spacecraft launched by the Space Shuttle]] [[Category:Spacecraft launched by Titan rockets]] [[Category:Equipment of the United States Space Force]] [[Category:Military equipment introduced in the 1960s]]
[[ja:アメリカ軍の衛星通信#DSCS]]