Electrostatic accelerometers for the Equivalence Principle test in space Original Research Article

Several missions aiming at a test of the Universality of Free Fall up to a resolution of 10−17 are presently being studied by space agencies. Electrostatic cryogenic differential accelerometers, including two concentric test masses made of different materials can be especially designed for these missions. The position and attitude of each test mass are measured with capacitive sensors and are servo-controlled through linear electrostatic actuators. In this way, a full electrostatic suspension is realised and the applied voltages on the electrodes constitute the accelerometer outputs. The sum of the measured accelerations will be nullified by the satellite drag-compensation system while the difference in the direction of the Earth (considered as the source of the gravitational attraction in this test) will be exploited for the detection of any violation signal. The proposed sensor-head configuration and the associated electrical functions have been optimised and the accelerometer performance is evaluated on the basis of realistic assumptions on the quality of the mechanics, the electronics and the instrument environment.