Robert V. Hilmer

Best Geosynchronous Earth Orbit Daytime Spacecraft Charging Index

Recently, the debate on what is the best daytime Geosynchronous Earth Orbit spacecraft charging index has been reopened. In this paper, the conclusions of one of the recent papers on the subject are verified by comparing Nascap-2k results with charging and fluxes measured on the Spacecraft Charging at the High Altitudes, Intelsat, Defense Satellite Communications System, and Los Alamos National Laboratory Geosynchronous Earth Orbit satellites. In addition, a refined measure of charging is presented as the total thermal electron flux above a certain minimum energy that is well above the second crossover point in secondary electron emission. The use of this type of index is justified by correlations between Nascap-2k simulation results and total fluxes above a range of energies. The best minimum energy to use is determined for spacecraft of different design and surface materials. Finally, the optimum Geosynchronous Earth Orbit daytime spacecraft charging index is obtained, and its use for predicting and res...

Space environment simulation and sensor calibration facility

The Mumbo space environment simulation chamber discussed here comprises a set of tools to calibrate a variety of low flux, low energy electron and ion detectors used in satellite-mounted particle sensors. The chamber features electron and ion beam sources, a Lyman-alpha ultraviolet lamp, a gimbal table sensor mounting system, cryogenic sample mount and chamber shroud, and beam characterization hardware and software. The design of the electron and ion sources presented here offers a number of unique capabilities for space weather sensor calibration. Both sources create particle beams with narrow, well-characterized energetic and angular distributions with beam diameters that are larger than most space sensor apertures. The electron and ion sources can produce consistently low fluxes that are representative of quiescent space conditions. The particle beams are characterized by 2D beam mapping with several co-located pinhole aperture electron multipliers to capture relative variation in beam intensity and a large aperture Faraday cup to measure absolute current density.