Aquacade (satellite)

Aquacade, previously designated Rhyolite, was a class of SIGINT spy satellites operated by the National Reconnaissance Office for the United States Central Intelligence Agency. The National Security Agency (NSA) was also reportedly involved. The program, also known by SIGAD AFP-720 and SIGAD AFP-472, respectively, is still classified. During the same period, the Canyon SIGINT satellites were in use with an apparently somewhat different set of capabilities.
History.
The name of the program, originally "Rhyolite", was changed to "Aquacade" in 1975 following the disclosure of the codeword "Rhyolite" in the trial of Christopher Boyce and Andrew Lee.
The Rhyolite/Aquacade satellites, made by TRW, are rumored to have an umbrella-like reflecting dish 20 meters in diameter. They were succeeded by the Magnum/Orion and Mentor series of satellites.
A major purpose of the Rhyolite satellites was reportedly the interception of Soviet and Chinese microwave relay signals traffic. During the 1960s-1970s, much of the long distance telephone and data traffic in both the US and Eastern Europe was carried by terrestrial microwave relay links, each consisting of a dish antenna on a microwave tower that transmitted a narrow beam of microwaves to a receiving dish in a nearby city. A good deal of the microwave beam would miss the receiving dish and, because of the curvature of the Earth, radiate out into space. By placing a satellite in a geosynchronous orbit at a position in the sky where it could intercept the beam, the US government was able to listen in on Soviet telephone calls and telex cables during the Cold War.
Satellites.
It is believed that at least four Rhyolite/Aquacade satellites were launched from Cape Canaveral between June 1970 and April 1978 on Atlas-Agena D launch vehicles, all of which sported distinctive elongated payload shrouds (presumably to house the satellite's large parabolic antenna). Secrecy around the program was tight and the initial Rhyolite mission in 1970 was the first space launch at Cape Canaveral in seven years that reporters were not invited to cover. These were among the final Atlas-Agena launches as well as the last use of LC-13 at CCAS. The satellites had a mass of approximately 700 kg and operated in near-geosynchronous orbits over the Middle East. Signals were relayed to a remote NSA Earth station in Australia, Pine Gap, out of range of Soviet detection. From there, they would be encrypted and sent via another satellite to the NSA's headquarters at Fort Meade for analysis.