Gang+Bao

The test mass of ASTROD I (the Astrodynamical Space Test of Relativity using Optical Devices I) will become charged due to exposure of the spacecraft to energetic particles in the space environment. Test mass charging will result in Coulomb and Lorentz forces and hence spurious test mass motions. To estimate the size of these effects, it is important to accurately model the test mass charging process. Earlier work, using GEANT 4 and a simplified ASTROD I geometry, predicted that the acceleration noise associated with test mass charging would be well below the ASTROD I residual acceleration noise target. Here we present results of a more accurate simulation, implementing a more realistic geometry model. We have simulated the charging processes due to cosmic-ray protons and alpha particles using this geometry model, at solar minimum and maximum. The magnitude of acceleration noise and stiffness associated with charging are estimated.
 * Further computation of the test mass charging and disturbances in ASTROD I **
 * G. Bao **** a, b ****, L. Liu **** a ****// , //**** b **** , D. Shaul **** c **** , H. Araújo **** c **** , W.-T. Ni **** a ** ** and T. Sumner **** c **
 * a **** Purple **** Mountain **** Observatory, CAS **
 * b **** Graduate **** University of the Chinese Academy of Science, Beijing **
 * c **** Department of Physics, Imperial College London, London, SW7 2BZ, UK **