Defense Satellite Communications System
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The Defense Satellite Communications System (DSCS) provides the United States with military communications to support globally distributed military users.
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[edit] Background
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.
[edit] Initial Defense Satellite Communications System (IDSCS)
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.
- IDSCS 1 launched 1966-06-16 1966-053 six satellites
- IDSCS launched 1966-08-26 (launch failure)
- IDSCS 2 launched 1967-01-18 1967-003 eight satellites
- IDSCS 3 launched 1967-07-01 1967-066 six satellites
- IDSCS 4launched 1968-06-13 1968-050 eight satellites
[edit] DSCS II
DSCS II provided secure voice and data communications for the U.S. military. The program was managed by the Defense Communications Agency (DCA), now DISA.
The space vehicles were spin stabilized with a despun 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.
[edit] DSCS III
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.
The spacecraft vehicle is 3-axis stabilization using reaction wheels, earth and sun sensors. Two articulated solar arrays 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.
The communications payload included six 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 gimballed dish.
[edit] DSCS III Service Life Enhancement Program (SLEP)
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.
[edit] References
- 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
