Analytic and Observational Approaches to Spacecraft Auroral Charging.

Abstract : The objective of this report is to present a set of computational tools which can be used to process large quantities of observations of auroral electron and ion fluxes to yield estimates of the likelihood of spacecraft charging. The tools and procedures would be tested on the DMSP observations of environments and spacecraft charging, and then be used to predict the levels of charging for the shuttle in polar orbits. We have presented two approaches. The first approach, the subject of Section II, is to fit the observed spectra to analytic functions which can then be manipulated to find the charging potential. The analytic functions proposed by Fontheim, et al., (1985), to represent electron flux spectra, are parameterized by a set of observable physical parameters. The second approach, described in Section III, is to numerically integrate the observations directly. The second approach is more appropriate for large numbers of spectra, while the first provides physical parameters which give insight to the nature of the precipitating electron environment. The appendix of this report is a user's manual for the computer programs which perform these tasks.