[Advanced VORTEX] The MERCURY signals intelligence spacecraft are designed to intercept transmissions from broadcast communications systems such as radios, as well as radars and other electronic systems. The interception of such transmissions can provide information on the type and location of even low power transmitters, such as hand-held radios. The MERCURY [Advanced VORTEX] spacecraft is believed to be built by Hughes, and to utilize a much larger military version of the special antenna that will be used on the commercial APMT mobile communications system.
Signals intelligence (SIGINT) consists of several categories. The VORTEX Communications intelligence (COMINT) system was originally developed by the Air Force for NRO to support NSA collection and exploitation of intercepted message traffic. The first CHALET spacecraft [as VORTEX was originally known] were first orbited in the late 1970's, and had an antenna with a diameter of several tens of meters. The most recent Advanced VORTEX spacecraft, since renamed MERCURY, have a very large deployable antennae with a diameter of approximately 100 meters. With the consolidation of all SIGINT programs under the NRO SIGINT Directorate, MERCURY has been redirected to additionally perform Electronic intelligence (ELINT) collection of non-communications electronic transmissions, to includ telemetry from missile tests (TELINT), or radar transmitters (RADINT).