Spacecraft Charging for Microsatellite KITSAT-3

Abstract

Floating potentials for a microsatellite KITSAT-3 are measured with an electron temperature probe. The orbit of the satellite is 730-km altitude, sun-synchronous, with a fixed local time of descending node near 1200 hrs local time. The dimension of the satellite in stowed configuration is approximately 495 × × 614 × 852 mm 3 . The weight of the satellite is 112 kg. In the dayside, a series of attitude maneuvering is performed to rotate the satellite. Significant correlation between the currents generated from the solar arrays and the floating potentials is found. The initial floating potentials that are largely negative (<−10 V) when the solar arrays are directed toward the sun are found to increase up to ∼ ∼− 3V as the rotation of the spacecraft brings the solar arrays nearly perpendicular to the sunlight. The result of the potential variation is verified by a numerical simulation with NASCAP/LEO. The present investigation finds that the floating potentials for a microsatellite KITSAT-3 are determined by the negative charging of the satellite due to the presence of solar arrays. Nomenclature AC = conductive area of the satellite body, m 2 AS = surface area of the satellite, m 2 AW = conductive area of interconnectors, m 2 B = magnetic field, nT e = electron charge, 1.60 × 10 −19 C I = current, A ISC = current collected in the ram direction by the orbital motion of the satellite, A ITH = current collected due to the satellite potential, A k = Boltzmann constant q= charge, C Vp = satellite potential, V Vpp = peak-to-peak voltage, V Vsc = orbital speed of satellite, m/s α = angle between the orbital velocity and the normal vector of the conductive surface �� = potential difference between the solar cells, V θ = angle of satellite orientation relative to the orbital velocity, deg