, previously known as Chalet
, is a class of reconnaissance satellite
operated by the United States
during the 1980s and 1990s to collect signals intelligence
(SIGINT) from high Earth orbit. The Vortex satellites were operated by the National Reconnaissance Office
for the United States Air Force
and listened to radio transmissions originating from Earth or space. The intercepted data is believed to have been fed into and analyzed by the National Security Agency ECHELON
The satellites weigh approximately 1,800 kilograms and are operated from geosynchronous orbits. Each reportedly carried a 38-meter-diameter umbrella-like reflecting dish to collect radio signals from Earth. At least six launch attempts were made of Chalet/Vortex satellites between 1978 and 1989. The Chalet/Vortex satellites replaced the older generation of Canyon satellites, and were superseded by the larger, more capable Mercury SIGINT satellites.
- Richelson, Jeffrey T. ed. U.S. Military Uses of Space, 1945-1991 Vol 1, Guide. National Security Archive. 1991.