GFZ-1
GeoForschungsZentrum-1

GFZ-1 is a geodetic satellite designed to improve the current knowledge of the Earth's gravity field. The satellite, a passive system with no onboard sensors or electronics, is covered with retroreflectors that reflect laser beams sent from ground stations. By measuring the round trip time of the transmitted light, the distance between the satellite and the station can be determined with approximately 1 centimeter. These measurements are used to determine variations in the rotational characteristics of the Earth and for measurement of the Earth's gravitational field. As the vehicle's orbit decays, the satellite's orbital motion will also be used calculate to atmospheric densities. Deployed from the Mir space station, GFZ-1 was the first non-Russian satellite launched from MIR. GFZ-1 was developed in under 12 months and cost approximately $700,000 (including design, fabrication, test, and launch). Data collection, distribution and evaluation is coordinated by the project's scientists at the GeoForschungsZentrum Potsdam.

Spacecraft
The satellite consists of a spherical body made from brass with 60 corner cube reflectors distributed regularly over the satellite's surface. These retroreflectors are quartz prisms placed in special holders that are recessed in the satellite's body. External metallic surfaces are covered with white paint for thermal control purposes and to facilitate visual observation in space. The vehicle's size was limited by the maximum allowable dimensions of the Mir airlock (30 cm). The vehicle carries no electronics or sensors and is not attitude controlled.

Payload
No payload. Science is performed using the vehicle's 60 retroreflectors.

Country of Origin	Germany
Customer/User	GeoForschungsZentrum Potsdam Science Institute
Manufacturer(s)	Kayser-Threde GmbH, Institute of Space Device Engineering, Moscow
Size	0.21 m dia. sphere
Orbit	382 x 395 km, incl. = 51.6 deg.
Design Life	Approx. 4 years

Launch Facts

Name	Int'l Desig.	Date	Site	Vehicle	Orbit	Mass(kg)
Notes
GFZ 1	1986-017JE	4/9/95	Tyuratam	SL-4	LEO	20
Geodetic; carried retroreflectors for ground laser ranging; deployed from Mir 4/19/95