Castor (satellite)

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Castor
Type: Research satellite
Country: FranceFrance France
Operator: CNES
COSPAR-ID : 1975-039B
Mission dates
Dimensions: 76 kg
Size: 80 cm diameter
Begin: 17th May 1975
Starting place: Kourou
Launcher: Diamond BP-4 No 2
Status: burned up February 18, 1979
Orbit data
Rotation time : 100.3 min
Orbit inclination : 28.9 °
Apogee height :  272 km
Perigee height :  1271 km
Eccentricity : 0.07

Castor (also known as D5-B ) is a French small satellite that was launched with the help of a diamond rocket together with the Pollux satellite.

Purpose and structure

Castor was almost spherical because the friction with the rest of the atmosphere should be independent of the orientation of the satellite. The surface was covered with 26 solar cells , which generated an electrical output of 20 W, as well as 26 laser reflectors , which enabled precise location by the ground stations.

The main payload was the accelerometer CACTUS (Capteur Accélérométrique Capacitif Triaxal UltraSensible), with which accelerations of 10 −5 to 10 −9  m / s 2 could be measured with an accuracy of 1.5%. This made it possible to determine the air resistance of the remaining atmosphere and thus also the density of the upper layers of the atmosphere. Further measurements of the orbit disturbances were used for geodesy , and micrometeorites were to be recorded.

The data acquisition was performed at intervals of either 0.1 s or 2.8 s. The telemetry data could be transmitted to the ground station in real time either with 256 bit / s or with 512 bit / s. The transfer of the memory with 131 kbit capacity was even possible with 1024 bit / s.

Mission history

Pollux (above) with Castor (below)

The first attempt to start on May 22, 1973 in Kourou failed because a protective cover did not come off. The start on May 17, 1975, however, was successful. Castor worked satisfactorily for several years until it re-entered the earth's atmosphere on February 18, 1979 and burned up.

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