Rhyolite 1, 2, 3, 4 / Aquacade 1, 2, 3, 4

The Rhyolite (later renamed to Aquacade, when the former name became public) are geostationary signals intelligence satellites. Their purpose was to intercept missile telemetry from the Soviet Union and China (TELINT). Unlike the Canyon SIGINT crafts, they were positioned in geostationary orbit.

The Rhyolite satellites were also known as Program 720 and Program 472. After the second launch, they were renamed in 1977 to Aquacade as the original name was leaked.

Prime contractor for the Rhyolite satellites was the Defense and Space Systems Group of TRW Inc, which in 1966 was awarded the contract to develop and build four Rhyolites in close cooperation with the CIA project design team. They had reportedly a mass of 700 kg. The design was dominated by a large unfurlable dish antenna with a diameter of about 20 to 23 m.

The satellites were launched by Atlas-SLV3A Agena-D with an extremely long payload fairing into a geostationary transfer orbit with final geostationary orbit insertion performed by the onboard apogee propulsion system.

Rhyolite 1 was launched on 19 June 1970 and was initially positioned at 105� East to monitor both the Baikonur and Sary Shagan test areas. It was regularly repositioned to monitor other areas of interest, like the India-Pakistan War in 1971 or the Vietnam war area. After the second satellite became operational, it was dedicated to the China and Vietnam observations on a long-term basis. It operated at least for five years and was reported still to be operational in late 1975.

Rhyolite 2 followed on 6 March 1973 and operated initially from 70� East over the Horn of Africa to monitor microwave transmissions from the western Soviet Union and telemetry from Baikonur launched ICBM tests. It remained there for about five years. It is unknown, if it ceased operating or was relocated to another position.

The third satellite launched under the new name Aquacade 3 on 11 December 1977 to replace Rhyolite 2 at the 70� East location. This satellite was reported to be still active in December 1982, although at the end of life.

The last satellite, Aquacade 4, was launched on 7 April 1978. Reportedly it was operated from a position at 115� East to monitor the re-entry telemetry from ballistic missile re-entry vehicles impacting around the Kamchatka Peninsula. Also targeted were microwave transmissions from the central and eastern Soviet Union. Aquacade 4 was also reported to be still active in December 1982 in an end of life condition.

These satellites were operated from the Pine Gap, Australia, ground station.

A replacement program called Argus with a 40 m antenna was planned, but this was cancelled. They were eventually succeeded in the 1980s by the Magnum / Orion series.