Orbital tests of the CACTUS accelerometer

The CACTUS accelerometer (French acronym meaning ultrasensitive, three-axis, capacitive accelerometric transducer) was developed at ONERA with a view to utilization in space experiments. Its measuring range is between 10 to the minus 8th power and 10 to the minus 4th power m/sec sq. The French satellite CASTOR, designed and placed in orbit by CNES (the French Space Agency) on May 17, 1975, had as primary objective the qualification in flight of the CACTUS accelerometer. After a brief historical account and a general presentation, the instrument, its means of calibration on the ground and in space, an analysis of causes of perturbations, and the corresponding verifications performed in orbit, as well as detailed results of the qualification experiments are described in detail. It appears evident that the resolution of the instrument is 2.10 to the minus 9th power m/sec sq.