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<div>The '''Defense Satellite Communications System''' ('''DSCS''') provides the [[United States]] with military communications to support globally distributed military users.<br />
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== Background ==<br />
DSCS went though three major phases. Since the first launch, DSCS has been the "workhorse" of military [[satellite communications]]. DSCS III satellites currently exceed their 10-year design life.<br />
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==Initial Defense Satellite Communications System (IDSCS)==<br />
[[Image:IDCSP 1.jpg|thumb|Eight IDSCS satellites]]<br />
The first stage of the DSCS program, initially called IDSCS, consisted of clusters of small (80 cm, 45-kg) satellites in slightly sub-synchronous (22.2 hour) orbits that drifted about thirty degrees to the east each day. Four out of the five launch attempts between June 1966 and June 1968 were successful. The program was renamed DSCS I when the system became operational, and the system transmitted reconnaissance photographs and other data during the Vietnam war. <br />
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*'''IDSCS 1''' launched 1966-06-16 [http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1966-053A 1966-053] six satellites<br />
*'''IDSCS ''' launched 1966-08-26 (launch failure)<br />
*'''IDSCS 2''' launched 1967-01-18 [http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1967-003A 1967-003] eight satellites<br />
*'''IDSCS 3''' launched 1967-07-01 [http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1967-066A 1967-066] six satellites<br />
*'''IDSCS 4'''launched 1968-06-13 [http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1968-050A 1968-050] eight satellites<br />
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==DSCS II==<br />
[[Image:DSCS-2 1.jpg|thumb|DSCS II satellite]]<br />
DSCS II provided secure [[circuit switching|voice]] and [[data communications]] for the U.S. military. The program was managed by the Defense Communications Agency (DCA), now [[DISA]].<br />
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The space vehicles were spin stabilized with a despun antenna platform. The body was mounted with [[solar cell]]s which produced 535 [[watt]]s. Three NiCd [[battery (electricity)|batteries]] provided electrical power and it was supported by a [[hydrazine]] propulsion subsystem.<br />
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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.<br />
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==DSCS III==<br />
[[Image:DSCS-3 1.jpg|thumb|DSCS III satellite]]<br />
DSCS III provides secure voice and data communications for the U.S. military. The program was also managed by DISA and the [[U.S. Air Force]]. <br />
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The spacecraft vehicle is 3-axis stabilization using reaction wheels, earth and sun sensors. Two articulated [[Photovoltaic module|solar array]]s produce 1240 watts and the space vehicle was supported with NiCd batteries. [[S-band]] and X-bands supported command and telemetry links. The propulsion subsystem was supported by a hydrazine as well.<br />
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The communications payload included six [[Super high frequency|SHF]] channels with full Earth and narrow coverage capabilities. Receive antennas included two Earth coverage horns and one configurabe 61-beam nulling antenna. Transmit antennas included two Earth coverage horns, two configurable 19-beam antennas and one high gain [[parabolic antenna|parabolic]] gimballed dish.<br />
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===DSCS III Service Life Enhancement Program (SLEP)===<br />
The DSCS SLEP provided performance enhancements for the last four DSCS III satellites. The enhancements were designed to increase the DSCS capacity by over 200 percent.<br />
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== References ==<br />
*[http://www.lockheedmartin.com/wms/findPage.do?dsp=fec&ci=11466&rsbci=12970&fti=0&ti=0&sc=400 Lockheed Martin's Page on DSCS]<br />
*[http://www.fas.org/spp/military/program/com/dscs_3.htm Federation of American Scientists - DSCS 3]<br />
*[http://www.losangeles.af.mil/SMC/MC/dscs.htm U.S. Air Force MILSATCOM - DSCS] <br />
*[http://msl.jpl.nasa.gov/Programs/dscs.html NASA JPL - DSCS]<br />
*[http://www.af.mil/factsheets/factsheet.asp?fsID=95 Air Force - DSCS III]<br />
*[http://nssdc.gsfc.nasa.gov/nmc/sc-query.html NASA's National Space Science Data Center (NSSDC) - Master Catalog - Spacecraft Query]<br />
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== See Also ==<br />
*[[Military_satellite|Military Satellite]]<br />
*[[Communications_satellite|Communications Satellite]]<br />
*[[Military_Strategic_and_Tactical_Relay_satellite|Milstar]]<br />
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[[Category:Communications satellites]]<br />
[[Category:Military communications]]</div>Gunter.krebs