Experimental demonstration of bias rejection from electrostatic accelerometer measurements

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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.