GROUND BASED TESTS OF ULTRA SENSITIVE ACCELEROMETERS FOR SPACE MISSION

摘要

Both CNES MICROSCOPE and ESA GOCE mission payloads are based on electrostatic accelerometers containing a proof mass whose position is controlled in six degrees of freedom (three translations, three rotations) via electrostatic forces. Their operations rely on the very precise control of the position and orientation of proof masses. Given the range of the accelerometer (a few 10~(-6) ms~(-2)), the performance verification requires a low gravity environment for on ground tests. Pendulum test benches, controlled on horizontality, and Drop Tower for free fall tests are the main facilities allowing complete accelerometer verification prior to launch.. A pendulum test bench, developed for laboratory tests, is a platform slaved to the horizontal by an active control of the inclination with respect to the vertical. The projection of the gravity g on the platform is limited within the accelerometer range by an appropriate design if the horizontal controls in the measurement range of the two ultra sensitive axes of the accelerometers. This test facility is used for verifying functionally and extensively the accelerometer channels.For an exhaustive verification, as microgravity environment is the only mean to fully test the accelerometers along all the three axes, freefall tests are conducted in the 120-meter high Bremen tower in ZARM that offers 4.7 seconds of freefall under vacuum.The paper illustrates the interest and efficiency of these facilities through the examples of the verification results of the two GOCE and MICROSCOPE missions.