Electrostatic charging of space-borne test bodies used in precision experiments

Space-borne physics experiments involving the measurement of small motions of test bodies are likely to be limited by disturbance forces. Of particular concern are forces arising from electrostatic charging of the test body due to interactions with particle radiation. Estimates of charging rates have been computed using Monte Carlo particle-transport codes in combination with semi-empirical particle flux models. Results are presented for the STEP and LISA geometries, and are extrapolated for GP-B. The consequences of the charging are assessed for each experiment, and a method for alleviating the problem is discussed which uses the photoemission technique already in the hardware development phase for GP-B.