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astronautix.com HS 381

HS-381 / Syncom 4
HS-381 / Syncom 4 -

Credit: Hughes. 9,995 bytes. 240 x 263 pixels.



Other Designations: Leased Satellite. Class: Communications. Nation: United States. Agency: USAF, US Navy, DCA. Manufacturer: Hughes.

The Leasat series was developed as a commercial venture to provide dedicated communications services to the U. S. military. The program was initiated as a result of Congressional reviews in 1976 and 1977 which advised increased use of leased commercial facilities. Owned by Hughes Communications, the satellites were designed to provide global UHF communications to military air, sea, and ground forces. The system's primary user is the US Navy, with some support also provided to the Air Force and ground mobile forces (using FLTSATCOM terminals). Hughes was paid $84M per year for each operational satellite. At the end of each satellites' designed 7 year life, the Navy has the option of purchasing the satellite for $15M. The Leasats, along with the Navy's FLTSATCOM spacecraft, are being replaced by the UFO (UHF Follow-on) spacecraft. Spacecraft: Hughes HS-381 bus. Spin stabilised at 30 rpm with despun communications and antenna section. Body mounted solar cells provide 1500 W BOL and NiCd batteries provide power in eclipse. Solid rocket motor for perigee burn, bipropellant system for apogee burn. Hydrazine system for station-keeping. The design is optimised for Shuttle launch and deployment. Payload: Five antennas on the despun platform provide full Earth coverage. Two UHF helices (30 cm diameter, 3.8 m long) one transmit, one receive. Two X-Band horns (one beacon, one receive). One omni TT&C antenna. Channel 1: X-Band uplink, UHF downlink, 25 kHz bandwidth for fleet broadcast using spread-spectrum anti-jamming protection. Channel 2: UHF, 500 kHz bandwidth. Channels 3 to 8: UHF, 25 kHz bandwidth. Channels 9 to 13: UHF, 5 kHz bandwidth.


Specification

Design Life: 7 years. Total Length: 2.7 m. Maximum Diameter: 4.2 m. Total Mass: 1,330 kg.


HS 381 Chronology


30 August 1984 Syncom IV-2 Launch Site: Cape Canaveral . Launch Vehicle: Shuttle. Mass: 1,315 kg. Perigee: 35,780 km. Apogee: 35,788 km. Inclination: 4.8 deg.

Released from STS 41D 8/31/84; 105 deg W; leased to U.S. government. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C).


08 November 1984 Syncom IV-1 Launch Site: Cape Canaveral . Launch Vehicle: Shuttle. Mass: 1,315 kg. Perigee: 36,144 km. Apogee: 36,413 km. Inclination: 3.1 deg.

Released from STS 51A 11/10/84; 105 deg W; leased to U.S. government. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C).


12 April 1985 Syncom IV-3 Launch Site: Cape Canaveral . Launch Vehicle: Shuttle. Mass: 1,315 kg. Perigee: 35,771 km. Apogee: 35,802 km. Inclination: 4.1 deg.

Released by STS 51D 4/13/85; failed to orbit and subsequently repaired by STS 51-I on 8/31/85; 178 deg E; leased by U.S. government. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C).


27 August 1985 Syncom IV-4 Launch Site: Cape Canaveral . Launch Vehicle: Shuttle. Mass: 1,388 kg. Perigee: 35,809 km. Apogee: 35,829 km. Inclination: 4.0 deg.

Released by STS 51I 8/29/85; 178 deg E; leased by U.S. government. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C).



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Last update 12 March 2001.
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© Mark Wade, 2001 .