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Aviation History
1985
1985 - 0114.PDF
INTERNATIONAL SATELLITE DIRECTORY Milstar Milstar is the next generation of US defence communications satellite, de signed to be highly survivable. The space craft themselves will be protected against attack by Soviet anti-satellite weapons, with orbital manoeuvring and shielding against radiation and lasers. The com munications payload will include extra high frequency (EHF) channels. This part of the radio frequency spectrum recovers more rapidly from the electromagnetic interference caused by high-altitude nuclear bursts intended to disrupt communications. The first Milstar will be launched in the late 1980s. The opera tional network will comprise four geo stationary satellites, plus three in highly elliptical polar orbit, plus several spares in 180,000km-high "dark" orbit. Payload UHF and EHF (44/20GHz) channels Owner US Department of Defence Manufacturer Lockheed Missiles & Space Orbit Geostationary and polar Cost $l,049m (1983)—one satellite, plus one option and long-lead items for a third. Remarks Hughes Aircraft and TRW are responsible for the payload. E-Systems will supply the UHF transponder suite. Satellites will have laser crosslinks to improve survivability. Nato III Nato III is the current generation of Nato-funded communications satellites, providing secure SHF links within Western Europe and between Europe and the USA. The operational network com prises four satellites, one an in-orbit spare. Nato III is interoperable with the US DSCS network. Purpose Communications satellite Payload 3 7/8GHz transponders Owner Nato Manufacturer Ford Aerospace Orbit Geostationary Launch/status Nato IIIA Apr 1976 Delta B Jan 1977 Delta/ used in DSCS C Nov 1978 Delta D Novl984/Delta/in-orbit spare Stabilisation Spin Power 0-4kW Weight (at launch) 700kg Design life 7 years. Navsat (Transit/Nova) Developed to provide periodic precise position updates to Polaris submarines, the US Navy's Navsat system services a wide range of military and civil users. RCA built 15 Transit spacecraft. Three were launched between 1968 and 1973, and they have so exceeded their three- year design lives that the remaining 12 were placed in ground storage. The US Navy has now decided to place eight more Transits in orbit, two at a time starting in 1985, under the Stacked Oscars On Scout programme. The Nova Satellite is an improved version of the Transit first launched in 1981. Three Novas have been ordered. Purpose Navigation satellite Operation Each satellite transmits continuously on 150 MHz and 400MHz. A user locates itself in relation to the satellite by measuring the Doppler shift of one or both of these signals during a Transit pass. As the satellite signal contains accurate orbit details, period ically updated by the Navsat ground station, the user is able to determine its own position to within 100m. Addi tionally, the Nova satellite introduces a pseudo-random noise ranging signal which enables the user to determine range and time. A constellation of five satellites provides an interval between fixes of 30-100min depending on latitude. Owner US Navy Manufacturer RCA Astro-Electronics Orbit Polar, circular, 1,075km high Launch Transit 18 Mar 1968 Scout 19 Aug 1970 Scout 20 Oct 1973 Scout 21-28 in pairs by Scout start ing in 1985. Nova 1 May 1981 Scout 2 Oct 1984 Scout Stabilisation Gravity gradient Power Transit 0-2kW Nova 0-65kW Weight (at launch) Transit 60kg Nova 165kg Remarks Nova features onboard station- seeking and station-keeping, requiring fewer updates from the ground and resulting in a more accurate system. Four Ford Aerospace-built Nato III communications satellites have been launched 1 42 FLIGHT International, 12 January 1985
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