On the spacecraft photo-emission efficiency in inner magnetosphere Original Research Article

The emission of photoelectrons from the surface of a satellite in conditions of low density plasma plays crucial role for the spacecraft structure potential, which sets up on the value defined by condition of the currents balance - at steady state conditions total current to the satellite body should be zero. It is commonly believed that in high-latitude inner magnetosphere at altitudes exceeding ∼1RE the spacecraft potential Usat is always positive. On the other side, two experiments at Interball-2 have shown (Smimova et al., 2002) that its potential was predominantly negative. One of possible reasons may be lowered photo emission efficiency in the Interball-2 case. As largest photo-emitting part of Interball-2 structure were flat solar panels, the photo-emission for flat model of a satellite have been calculated for variety of the satellite parameters, including the negative spacecraft potential, and ambient conditions using close-to-real model of electric field distribution around the satellite body. Results of modeling are presented. The largest impact on spacecraft potential comes from the presence of the ambient magnetic field, its orientation, and the size of spacecraft body. In particular, it is shown that in some cases large input to the photoemission efficiency arises from collection of photoelectrons by backward surface of the satellite.