GFZ-1 (GeoForschungsZentrum-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 轜,000 (including design, fabrication, test, and launch).
Data collection, distribution and evaluation is coor dinated 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.
[Source: NASA Mission and Spacecraft Library]