The Chalet / Vortex / Mercury ELINT satellites were the successors to the Canyon series of near GEO ELINT/SIGINT satellites of NRO's Program A. They were focussed on communications intelligence (COMINT), but had the capability added to intercept also missile telemetry. These satellites were launched under the designation Program 7500.
Reportedly they consist of a large (ca. 38 m diameter) antenna and are three axis stabilized. They were deployed into a 24 h orbit, which was not geostationary, so that triangulations of emitter sources can be made from different points. The satellites of this series were injected directly into the final orbit by the launch vehicle's upper stage, so they did not feature an apogee propulsion system.
The numbering sequence continued the earlier Canyon sequence. The name was changed from Chalet to Vortex, when the former name was disclosed in a New York Times report in 1979. They are also known as AFP-366 series. When the name Vortex was revealed in 1987, the satellites were renamed Mercury.
These satellites proved to be extraordinary long lived. Vortex 10 operated for more than 25 years.
The successor of these satellites were the Mercury 14 - 16 geostationary ELINT satellites.
|Type / Application:||SIGINT, COMINT, ELINT|
|Configuration:||~ 38 m Ø Dish Antenna, 3-Axis-Stabilization|
|Power:||Solar arrays, batteries|
|Lifetime:||+25 years (reached #10)|
|Mass:||932 kg ?|
|Orbit:||30200 km × 40800 km, 7.00° (typical)|
|Chalet 8 → Vortex 8 (Mission 7508, OPS 9454)||1978-058A||10.06.1978||CC LC-40||Titan-3(23)C|
|Vortex 9 (Mission 7509, OPS 1948) (ex Chalet 9)||1979-086A||01.10.1979||CC LC-40||Titan-3(23)C|
|Vortex 10 → Mercury 10 (Mission 7510, OPS 4029) (ex Chalet 10)||1981-107A||31.10.1981||CC LC-40||Titan-3(23)C|
|Vortex 11 → Mercury 11 (Mission 7511, OPS 0441) (ex Chalet 11)||1984-009A||31.01.1984||CC LC-40||Titan-34D Transtage|
|Mercury 12 (Mission 7512, USA 31) (ex Vortex 12 ex Chalet 12)||1988-077A||02.09.1988||CC LC-40||f||Titan-34D Transtage|
|Mercury 13 (Mission 7513, USA 37) (ex Vortex 13 ex Chalet 13)||1989-035A||10.05.1989||CC LC-40||Titan-34D Transtage|