Charging of Geostationary Satellite Electro-L2 in the Earth Shadow

Magnetosphere plasma electron and proton fluxes in the energy range 0.04-11.3 keV were measured using electrostatic spectrometers established onboard the geostationary Electro-L2 spacecraft (point of standing 76 degrees EL). Measurements were done in the lit orbit segments and in the Earth shadow during the periods of vernal and autumn equinox in 2016-2017. In terms of the observation data, fluxes, and parameters of the plasma particles for different geomagnetic activity levels and potentials of the spacecraft metal base were determined. The measured values of the negative spacecraft metal base potential achieve 5-10 kV in the Earth shadow. Interpretation of the measurement results was done using the results of the spacecraft charging modeling obtained with the COULOMB-2 program package. Electric field gauges (EFGs) and electrostatic discharge (ESD) gauges were established on the spacecraft surface as well. The electrostatic spectrometers data and the COULOMB-2 results coincide with the EFGs data. ESDs were registered onboard the spacecraft during the spacecraft entrance into the Earth shadow and exit from the shadow.