The
Rhyolite series was a run of four
intelligence satellites produced and orbited by the
U.S. government. Used for
ELINT purposes, the
Rhyolites could pick up
microwave leakage from short-range
telephone connections; when the signal (which was typically aimed at a microwave horn receiver on a tower or building) was sent, some
radiation inevitably missed the horn and continued straight past it. This meant, naturally, that it reached earth
orbit some thousands of miles later. The
Rhyolite birds were parked in
geostationary orbits so as to be able to listen in on microwave leakage escaping from the
porous telecommunications network of the
Soviet Union during the
Cold War. Their other (and some say primary) purpose was to intercept
telemetry signals, such as those used to control and monitor
ballistic missile tests.
All four Rhyolites were launched from Cape Canaveral, Florida. The first was launched on June 19th, 1970, aboard an Atlas/Agena rocket; the second followed it nearly three years later. The third went up in December of 1977, and the fourth and final Rhyolite launched on April 7th, 1978. Although some sources claim the first was a failure, its inclination indicating that it was left in its transfer orbit without making it to its assigned geo-synchronous orbit position, the three-year gap before the next launch would seem to indicate that it was, in fact, usable.
During the espionage trial of Christopher Boyce (the Falcon, of the spy team The Falcon and the Snowman), the name of the Rhyolite program was used in public forum. To protect the source of further intelligence, the satellites and their supporting program were rechristened Aquacade and remained such until their unmasking and deactivation.
The Rhyolite/Aquacade birds orbited at geostationary altitude, around 33,769 km above the Earth At launch, the payload package weighed approximately 700 kg . The second through fourth satellites had an orbital inclination of 0.2 degrees or less, being true geosynch. Once deployed, these satellites boasted a receiving antenna that was 20 meters across.
Sources:
- Deep Black by William Burrows
- David Hastings' SIGINT Satellites page at http://users.ox.ac.uk/~daveh/Space/Military/milspace_sigint.html#rhyolite
- Rocketry.com's launch listings.