Milstar
constellation of American military satellites
Milstar (Military Strategic and Tactical Relay) is a constellation of military communications satellites in geosynchronous orbit, which are operated by the United States Space Force, and provide secure and jam-resistant worldwide communications to meet the requirements of the Armed Forces of the United States. Six spacecraft were launched between 1994 and 2003, of which only five were operational after launch; the third launch failed, both damaging the satellite and leaving it in an unusable orbit.
History
Milstar Block I spacecraft, or Milstar Developmental Flight Satellite (DFS)-1 and -2, were designed with a Low Data Rate (LDR) payload in the +X wing of the satellite that broadcast in the Super High Frequency (SHF) and Extremely High Frequency (EHF) ranges, and also a classified communication payload in the -X wing. The DFS-1 satellite was launched on 7 February 1994 aboard the first Titan IV(401)A rocket, but with the classified -X wing payload deactivated. It was followed by the DFS-2 spacecraft on 7 November 1995. DFS-2 was similar to DFS-1, but the classified payload was replaced by ballast in the form of a precision machined aluminum block to maintain the weight and balance characteristics of the satellite. Both Block I satellites (USA-99 and USA-115) are still operational as of March 2025, over 30 years since they were launched.
The four later satellites were Block II spacecraft, which featured an additional medium data-rate payload. The first Block II satellite (DFS-3m, a hybrid mix of largely Block I support systems and LDR payload and a MDR (Medium Data Rate) Block II payload) was launched on 30 April 1999, using a Titan IV(401)B rocket. Due to a database error affecting the attitude control system of the Centaur upper stage of its carrier rocket, it was placed into a lower orbit than had been planned, and damaged by deployment at excessive rates.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jun 26, 2026. The linked authority identifier is Q1759462. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1994, 2003, 1995 and 2025.
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This entry incorporates text from “Milstar” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.