Numerical simulation of high-voltage charging of rotating satellites at high altitude

Summary form only given. Computer simulation of spacecraft (SC) charging is one of the main means for the analysis of SC interaction with the hot plasma space environment. Results of two computer codes are presented: NASCAP (NASA Charging Analyzer Program, USA) and ECO-M (Electrization of Cosmic Objects, Russia). Both were applied to the simulation of high-voltage charging of a rotating SC. The analysed SC model is a conducting cylinder (height 1 m, diameter 0.5 m.) covered by thin (0.1 mm) dielectric material. The cylinder rotates (1 rpm) around its long axis which is normal to the Sun direction. The plasma environment is described by an isotropic Maxwell distribution function for electrons and ions with equal temperatures (n/sub e/=n/sub i/=1 cm/sup -3/, T/sub e/=T/sub i/=10 keV). Secondary emission processes such as SEE, SIE and photo-emission have been taken into account. Together with solar irradiation all parameters correspond to realistic conditions for SC in geostationary orbit during a magnetic substorm. The currents to the satellite surfaces are computed by treating each surface element as a current-collecting probe. Time dependency is included in the analysis. Two cases were analysed by both codes: (a) a continuously rotating cylinder; (b) rotation starts after equilibrium charging was reached for a fixed orientation. In the first case the potential of illuminated SC surfaces increases steadily from 0 up to a steady-state level of about -10 kV relative to space with oscillations resulting from the SC rotation frequency. The oscillation amplitude is about 60-80 V. In the second case a rapid potential jump after the beginning of rotation is observed.