The US Air Force launched a $800m military communication satellite into orbit in late February 2001, after problems with electronic equipment, scheduling conflicts and rocket safety concerns were overcome. From the final orbit 22,300 miles high, the Milstar provides jam-proof, ultra-high-frequency and high data rate communications, both tactical and strategic, over the next decade. It instantly links bombers, missiles and submarines, fighter pilots and troops on the ground.
A follow-on of the Milstar satellite communication system, advanced extremely high-frequency (AEHF), or Milstar 3, was unveiled on 4 March 2009. The AEHF will improve the communication connectivity to provide state-of-the-art communication and network-centric war capabilities.
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The first AEHF satellite will be launched on board Atlas V launch vehicle in 2010. The second satellite will be launched in 2011 and the third in 2012. The programme is currently in the initial stages of adding a fourth satellite to the AEHF system.
Milstar satellite communications constellation
Milstar is a military satellite communications system that provides the Department of Defense and troops in the field with reliable, secure, jam-proof communications between fixed-site, mobile and portable terminals.
The Milstar system is composed of three segments. These are the space segment, comprising six satellites, the terminal segment, composed of communications terminals installed on ships, submarines, aircraft and vehicles, and the mission control segment, based at Falcon Air Force Base, Colorado Springs, Colorado.
The Milstar programme is led by the MILSATCOM Joint Program Office at the Air Force Space and Missile Systems Center in El Segundo, CA. The in-orbit system is managed by the US Space Command at Falcon Air Force Base, CO.
Milstar block II spacecraft
Of the five Milstar satellites that constitute the constellation, two first-generation Milstar block I were deployed in 1994 and 1995. Block I satellites feature a low data rate payload built by TRW Space and Electronics Group, El Segundo, CA, and two satellite crosslink antennas, built by Boeing Satellite Systems, El Segundo, CA. Both of the Milstar I spacecraft, DFS-1 and DFS-2, were launched on Lockheed Martin Titan boosters from Cape Canaveral Air Station, FL.
Three subsequent launches deployed a second-generation Milstar block II spacecraft (DFS-4 through DFS-6), which carry the low data rate payload and a medium-data-rate payload. DFS-4 through DFS-6 operate in conjunction with both block I satellites. They provide secure communications with ultra-high-frequency (UHF), extremely-high-frequency (EHF) and super-high-frequency (SHF) band transmitters.
Milstar 3 AEHF satellite system
The Milstar 3 AEHF satellite system consists of four satellites that cover the Earth from 65°N to 65°S. It will provide ten times the data rate of the original Milstar and form an important part of the military satellite communication systems of the Department of Defense.
The total cost of the AEHF programme was $2.5bn.
Communication networks
Milstar was the first satellite communications system of any kind that uses signal processing algorithms on the satellites, allowing commanders from every service to establish customised networks within minutes. Current networks must be configured on the ground, require multiple remote locations and can take weeks to establish using existing commercial and military systems.
Milstar communicates via terminals that are compatible among all the military services, including shipborne, man-portable, vehicle-mounted and carried in command and control aircraft. Each terminal transmits and receives voice and data in the extremely-high-frequency and super-high-frequency spectrum.
The low-data-rate payload is designed to transmit voice, data and fax information at 75bps to 2,400bps. The medium data payload, making its debut on the first Milstar II spacecraft transmits 1.5Mbps.
This combination of data rates and operational frequencies provides US military forces with capabilities not available on current Defense Satellite Communications System satellites or through commercial systems. These capabilities include immunity to jamming and interception and increased mobility for sea, air and ground forces. The Milstar satellite provides enhanced communication security by frequency hopping, which is a first for communication satellites.
Contractors
Lockheed Martin Space Systems Sunnyvale Operations, Sunnyvale, California, is the prime contractor. TRW Space and Electronics Group provided the low-data-rate payload. Boeing Satellite Systems provided the medium-data-rate payload for Milstar block II. Space Systems Denver provided the Titan IV launch vehicle and the wide-body Centaur upper stage. Milstar launches are managed by the 45th Space Wing, Patrick Air Force Base, Florida.
The contract for the AEHF satellite system was awarded to a group of companies including Hughes, Lockheed Martin and TRW.
