Milstar

History

The Milstar program began with two Block I spacecraft, designated Milstar Developmental Flight Satellite (DFS)-1 and -2. DFS-1 launched on 7 February 1994 aboard the first Titan IV(401)A rocket, with its classified communication payload deactivated. DFS-2 followed on 7 November 1995, carrying a precision machined aluminum block as ballast in place of the classified payload. Both Block I satellites remain operational as of March 2025.

Four later satellites were Block II spacecraft, which added a medium data-rate payload. The first Block II satellite, DFS-3m, launched on 30 April 1999 using a Titan IV(401)B rocket. A database error in the Centaur upper stage's attitude control system placed it in a lower orbit than planned and damaged it; it could not reach its operational orbit and was turned off after 10 days. The remaining three satellites—DFS-4, -5, and -6—launched on 27 February 2001, 15 January 2002, and 8 April 2003.

The Milstar system comprises three segments: the space segment of six satellites, ground terminals and users, and command and control stations. The Military Satellite Communications Systems Wing at Los Angeles AFB handled development and acquisition of the space and mission control segments, while the Electronic Systems Center at Hanscom AFB managed the terminal segment. The 4th Space Operations Squadron at Schriever SFB and the 148th Space Operations Squadron at Vandenberg SFB provide real-time satellite control and communications payload management.

Characteristics

Milstar satellites were built by Lockheed Martin Missiles and Space Corporation at a cost of US$800 million each, with a design life of 10 years. Each satellite has a mass of 4500 kg and solar panels generating eight kilowatts of power.

Block I and Block II satellites provide low data-rate communications from 75 bit/s to 2,400 bit/s; Block II spacecraft additionally offer medium data-rate communications between 4.8 kbit/s and 1.544 Mbit/s. Uplinks operate in the Q band (extremely high frequency), while downlinks operate in the K band (super high frequency). All six launches used Titan IV rockets with Centaur upper stages from Space Launch Complex 40 at Cape Canaveral Air Force Station.