Encyclopedia Astronautica
HS 381



hs381sy4.jpg
HS-381 / Syncom 4
Credit: Hughes
American military communications satellite. 4 launches, 1984.08.30 (Syncom IV-2) to 1985.08.27 (Syncom IV-4). The Leasat HS 381 series was developed as a commercial venture to provide dedicated communications services to the U. S. military.

Owned by Hughes Communications, the satellites were designed to provide global UHF communications to military air, sea, and ground forces.

The Leasat program was initiated as a result of Congressional reviews in 1976 and 1977 which advised increased use of leased commercial facilities. The system's primary user was 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 had the option of purchasing the satellite for $15M. The Leasats, along with the Navy's FLTSATCOM spacecraft, were later replaced by the UFO (UHF Follow-on) spacecraft. The spacecraft used a Hughes HS-381 bus, spin stabilized at 30 rpm with despun communications and antenna section. Body mounted solar cells provided 1500 W BOL and NiCd batteries provided power in eclipse. A solid rocket motor was used for perigee burn, and a bipropellant system for apogee burn. A hydrazine system was used for station-keeping. The design was optimized for Shuttle launch and deployment. The payload included five antennas on the despun platform, which provided full Earth coverage. These included two UHF helices (30 cm diameter, 3.8 m long) were fitted, one for one transmit, one for receive; two X-Band horns (one beacon, one receive); and one omni TT&C antenna. Channel 1 was used for X-Band uplink, UHF downlink, 25 kHz bandwidth for fleet broadcast using spread-spectrum anti-jamming protection. Channel 2 was UHF, with 500 kHz bandwidth. Channels 3 to 8 were UHF, 25 kHz bandwidth. Channels 9 to 13 were UHF, 5 kHz bandwidth.

AKA: Leased Satellite.
Gross mass: 1,330 kg (2,930 lb).
Height: 2.70 m (8.80 ft).
First Launch: 1984.08.30.
Last Launch: 1985.08.27.
Number: 4 .

More... - Chronology...


Associated Countries
Associated Engines
  • R-4D Marquardt N2O4/MMH rocket engine. 0.490 kN. Isp=312s. Developed as attitude control thruster for the Apollo Service and Lunar Modules in 1960s. In production for numerous satellites for apogee / perigee maneuvers, orbit adjustment, and attitude control. More...

See also
  • Shuttle The manned reusable space system which was designed to slash the cost of space transport and replace all expendable launch vehicles. It did neither, but did keep NASA in the manned space flight business for 30 years. More...

Associated Launch Vehicles
  • Shuttle American winged orbital launch vehicle. The manned reusable space system which was designed to slash the cost of space transport and replace all expendable launch vehicles. It did neither, but did keep NASA in the manned space flight business for 30 years. Redesign of the shuttle with reliability in mind after the Challenger disaster reduced maximum payload to low earth orbit from 27,850 kg to 24,400 kg. More...

Associated Manufacturers and Agencies
  • USN American agency overseeing development of rockets, spacecraft, and rocket engines. USN Joint Task Force 7, USA. More...
  • USAF American agency overseeing development of rockets and spacecraft. United States Air Force, USA. More...
  • Hughes American manufacturer of rockets, spacecraft, and rocket engines. Hughes Aircraft Co. , USA More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: here.
  • McDowell, Jonathan, Launch Log, October 1998. Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Cape Canaveral LC39A Shuttle, Saturn V launch complex. LC39A and LC39B, part of the Kennedy Space Center, were built on Merritt Island (north/northwest of the Cape) to support the Saturn V/Apollo lunar landing program. The sites were modified in the last half of the 1970s to support the manned Space Shuttle program. Construction began in December 1963. Complex 39A was completed on 4 October 1965. Complex 39A supported two unmanned and nine manned Saturn V/Apollo missions between 9 November 1967 and 8 December 1972. The site also supported the launch of the Skylab space station on 14 May 1973. Both complexes were modified to support Space Shuttle missions later on. Complex 39A supported the first Space Shuttle launch on 12 April 1981. More...

HS 381 Chronology


1984 August 30 - . 12:41 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC39A. LV Family: Shuttle. Launch Vehicle: Shuttle. LV Configuration: Space Shuttle 41-D.
  • Syncom IV-2 - . Payload: Discovery F1 / SBS 4 [PAM-D] / Telstar 302 [PAM-D]. Mass: 1,315 kg (2,899 lb). Nation: USA. Agency: HCI. Class: Communications. Type: Civilian communications satellite. Spacecraft: HS 381. Completed Operations Date: 1996-10-10 . USAF Sat Cat: 15236 . COSPAR: 1984-093C. Apogee: 36,741 km (22,829 mi). Perigee: 36,448 km (22,647 mi). Inclination: 13.0000 deg. Period: 1,477.60 min. 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). Positioned in geosynchronous orbit at 105 deg W in 1984-1987; 177 deg W in 1987; 72 deg E in 1988-1990; 177 deg W in 1990-1996 As of 1 September 2001 located at 17.02 deg W drifting at 10.139 deg W per day. As of 2007 Mar 10 located at 57.99E drifting at 10.147W degrees per day.

1984 November 8 - . 12:15 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC39A. LV Family: Shuttle. Launch Vehicle: Shuttle. LV Configuration: Space Shuttle 51-A.
  • Syncom IV-1 - . Payload: Discovery F2 / Anik D2 / Syncom-4 1. Mass: 1,315 kg (2,899 lb). Nation: USA. Agency: HCI. Class: Communications. Type: Civilian communications satellite. Spacecraft: HS 381. Completed Operations Date: 1992-09-26 . USAF Sat Cat: 15384 . COSPAR: 1984-113C. Apogee: 36,403 km (22,619 mi). Perigee: 36,152 km (22,463 mi). Inclination: 7.6000 deg. Period: 1,461.20 min. Released from STS 51A 10 November 1984; 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). Positioned in geosynchronous orbit at 15 deg W in 1984-1992 As of 3 September 2001 located at 170.37 deg W drifting at 6.220 deg W per day. As of 2007 Mar 10 located at 100.08W drifting at 6.233W degrees per day.

1985 April 12 - . 13:59 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC39A. LV Family: Shuttle. Launch Vehicle: Shuttle. LV Configuration: Space Shuttle 51-D.
  • Syncom IV-3 - . Payload: Discovery F4 / Anik C1 [PAM-D] / Syncom-4 3 [Orbus. Mass: 1,315 kg (2,899 lb). Nation: USA. Agency: HCI. Class: Communications. Type: Civilian communications satellite. Spacecraft: HS 381. Completed Operations Date: 1996-09-30 . USAF Sat Cat: 15643 . COSPAR: 1985-028C. Apogee: 37,080 km (23,040 mi). Perigee: 36,401 km (22,618 mi). Inclination: 14.4000 deg. Period: 1,485.10 min. 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). Positioned in geosynchronous orbit at 175 deg W in 1985-1987; 105 deg W in 1987-1996 As of 31 August 2001 located at 106.85 deg E drifting at 11.920 deg W per day. As of 2007 Mar 10 located at 158.41W drifting at 11.917W degrees per day.

1985 August 27 - . 10:58 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC39A. LV Family: Shuttle. Launch Vehicle: Shuttle. LV Configuration: Space Shuttle 51-I.
  • Syncom IV-4 - . Payload: Discovery F6 / Syncom-4 4 [Orbus-7S] / Aussat A1 [. Mass: 1,388 kg (3,060 lb). Nation: USA. Agency: HCI. Class: Communications. Type: Civilian communications satellite. Spacecraft: HS 381. Completed Operations Date: 1996-10-30 . USAF Sat Cat: 15995 . COSPAR: 1985-076D. Apogee: 36,503 km (22,681 mi). Perigee: 36,486 km (22,671 mi). Inclination: 9.5000 deg. Period: 1,472.40 min. 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). Positioned in geosynchronous orbit at 177 deg W in 1985-1987 As of 3 September 2001 located at 149.81 deg W drifting at 8.908 deg W per day. As of 2007 Mar 10 located at 84.34W drifting at 8.912W degrees per day.

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