Milstar

Description: Milstar is a constellation of geosynchronous satellites built by Lockheed Martin to provide secure, jam resistant and worldwide communications for high priority military users. The communications spectrum covers voice, data, imagery and video teleconferencing. This constellation supports the United States joint services linking command authorities with a wide variety of resources, including ships, submarines, aircraft and ground stations. Milstar is deemed the most advanced communication satellites deployed to date. Five spacecraft with a mass of 10,000 pounds and a planned service life of 10 years into Earth orbit at an altitude of 22,250 nautical miles (41,000+ km) form the Milstar constellation. Into space the power supply comes from 8,000 watts solar panels.

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. The ground stations are both mobile and fixed-position providing durable and survivable command and control over the satellite constellation.

Milstar I or Milstar Block I satellites were equipped with a UHF (Ultra High Frequency) and Low Data Rate EHF (Extremely High Frequency) payload provided by Northrop-Grumman as well as with crosslink payloads to communicate with other on-orbit satellites. The first Milstar I was launched February 7, 1994; the second November 5, 1995; and the third April 30, 1999, with this satellite placed into a non-usable orbit. Milstar II or Milstar Block II feature increased capacity through the addition of Medium Data Rate payload provided by Boeing. This payload process data at speeds up to 1.5 megabits per second. The Milstar II satellites were launched February 27, 2001; January 15, 2002; and April 8, 2003. All Milstar satellites were put into orbit by Centaur upper stage carried by a Titan IVB space launch vehicle.

Milstar systems consists of three segments: space (the satellites), terminal (the users) and mission control. Milstar I payload provides data rate communications at 75 bps to 2,400 bps. Milstar II provides the same data rate of Miltar I plus a data rate communications at 4.8 kbps to 1.544 bps from the medium data rate payload. The system was widely used in support of Operation Iraqi Freedom in 2003 and during hurricane relief operations in 2005. In November 2005 the US Air Force had five Milstar satellites operational. Three of those satellites should be replaced by AEHF, also known as the Milstar III, satellites starting in 2007. In the long run, US Air Force plans for the Milstar constellation to be superseded by TSAT starting in the next decade.

Specifications
Weights: Max Weight 4,536 kg (10,000 lb)

Performance: Orbit 41,207 km (22,250 nm), Service Life 10 yr