Science Fair Project Encyclopedia
Military Strategic and Tactical Relay satellite
Military Strategic and Tactical Relay satellite (MILSTAR) is a United States government satellite communications system that provides secure, jam resistant, worldwide communications to meet wartime requirements for United States military users.
Milstar is the most advanced U.S. military communications satellite system to date. It is a joint service system, i.e. it serves the communication requirements of the United States Army, Navy, and Air Force. The operational Milstar satellite constellation consists of five satellites positioned around the Earth in geosynchronous orbits. Each mid-latitude satellite weighs approximately 10,000 lb (4,536 kg) and has a design life of 10 years.
Each Milstar satellite serves as a smart switchboard in space by directing traffic from terminal to terminal anywhere on the Earth. Since the satellite actually processes the communications signal and can link with other Milstar satellites through crosslinks, the requirement for ground controlled switching is significantly reduced. The satellite establishes, maintains, reconfigures and disassembles required communications circuits as directed by the users. Milstar terminals provide encrypted voice, data, teletype or facsimile communications. A key goal of Milstar is to provide interoperable communications among the users of Army, Navy, and Air Force Milstar terminals.
Geographically dispersed mobile and fixed control stations provide survivable and enduring operational command and control for the Milstar constellation.
The first Milstar satellite was launched 7 Feb , 1994 aboard a Titan IV expendable launch vehicle. The second was launched 5 Nov 1995. The third launch on 30 April 1999, placed the satellite in a non-usable orbit. The fourth through six satellites have a greatly increased capacity because of an additional medium data rate payload and were launched on 27 Feb 2001, 15 Jan 2002, and 8 April 2003.
The Milstar system is composed of three segments: space (the satellites), terminal (the users) and mission control. Air Force Space Command's Space and Missile Systems Center at Los Angeles Air Force Base , California, is responsible for development and acquisition of the Milstar space and mission control segments. The Electronic Systems Center at Hanscom AFB, Massachusetts, is responsible for the Air Force portion of the terminal segment development and acquisition. The 4th Space Operations Squadron at Schriever AFB, Colorado, is the front line organization providing real-time satellite platform control and communications payload management.
- Primary function: Global military communications system
- Primary contractor: Lockheed Martin Missiles and Space
- Power plant: Solar panels generating 8 kW
- Weight: ~10,000 lb (4,500 kg)
- Orbit altitude: 22,250 nautical miles (41,200 km) geosynchronous
- Low data rate communications (voice, data, teletype and facsimile) at 75 bit/s to 2,400) bit/s (All satellites)
- Medium data rate communications (voice, data, teletype, facsimile) at 4.8 kbit/s to 1.544 Mbit/s (Satellites 4 through 6 only)
- Launch vehicle: Titan IVB/Centaur upper stage
- Inventory: 5
- Unit Cost: $800 million
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