Experimental demonstration of bias rejection from electrostatic accelerometer measurements

In order to test gravitation in the Solar System, it is necessary to improve the orbit restitution of interplanetary spacecrafts. The addition of an accelerometer on board is a major step toward this goal because this instrument measures the non-gravitational acceleration of the spacecraft. It must be able to perform measurements at low frequencies with no bias to provide an additional observable of interest. Since electrostatic accelerometers suffer a bias, a technological upgrade has been proposed by Onera. It consists in adding to an electrostatic accelerometer a rotating platform which allows modulating the signal of interest and retrieving it without bias after post-processing. Using this principle, a measurement method and a post-processing method have been developed. The objective of this article is to validate these methods experimentally. To do so, a horizontally controlled pendulum was used to apply a known signal to an accelerometer mounted on a rotating platform. The processing of the experimental data demonstrates the ability to make acceleration measurements with no bias. In addition, the experimental precision on the unbiased acceleration obtained after post-processing corresponds to the precision predicted theoretically.