Geosat

Geosat ( Geodetic Satellite ) was an Earth observation satellite of the U.S. Navy, which was equipped with a radar altimeter, and satellite geodesy and the ocean topography served. The satellite was launched on 12 March 1985 at a scaled down and to the satellite carrier converted Atlas -E ICBM from Vandenberg AFB into a polar orbit (757 x 814 km, 108.1 °).

Construction of the satellite

The based on the structure of the GEOS -3 satellite body of the satellite weighed 635 kg and was developed by the Applied Physics Laboratory of Johns Hopkins University.

As a scientific instrument, the GRA ( Geosat radar altimeter ), which was developed based on the altimeter of the NASA satellite Seasat served. Thus, the sea level could be measured with a vertical accuracy of 3 cm. The horizontal resolution was 10 - 15 km. The data of up to 12 hours of measurements were recorded using two tape recorders and transfer when flying over the ground station via a S- band telemetry system.

The power supply was secured by eight solar boom is folded down. The satellite was aligned on a full- Retracted on a boom weight due to gravitational stabilization with a deviation of less than 1 ° perpendicular to the ground.

Mission

Geosat determined by means of the radar altimeter the exact distance between the sea surface and its accurately known orbit. The aim was to determine the spatial and temporal changes of sea level.

The mission of Geosat was divided into two phases:

• In the first 18 months was operated as a primary mission a secret geodetic surveying the oceans. Therefore, the satellite was in an orbit with non- repetitive overflight cycle. The data from this survey allowed a more accurate image of the Earth's gravity and thus an increased accuracy of submarine launched ballistic missiles.

• In the second phase, which lasted from September 1986 to January 1990, the science accessible geodetic data were obtained. For the orbit has been changed so that the overflight repeated over a certain spot every 17 days. Due to the orbit, the mission phase as ERM ( Exact Repeating mission) was designated

In January 1990 ended the operability with the failure of both data recorder. By the year 1995, several steps were all released to date secret survey data.

Follow-up missions

After the end of the life of the Geosat satellite mission should be continued by a mounted on the planned for the early 1990s, ocean observation satellites N- ROSS radar altimeter. As N- ROSS was deleted for reasons of cost, the U.S. Navy was planning the radar altimeter as the sole instrument on the Mikrosateliten SALT to start, but this was also deleted. Only in 1998 was the Geosat Follow -On satellite will have a follow-up mission available.