Correlation of self-contamination experiments in orbit and scattering return flux calculations

Gaseous emissions from a spacecraft modify the orbital environment degrade the observations of distant radiation sources, and provide contamination fluxes induced by self-scattering and scattering with ambient particles. Experiments were carried out on the orbiting Atmospheric Explorer-D satellite (AE-D) to verify the calculated return fluxes of a neon source. Known rates of neon were emitted in the direction of the velocity on command to the Molecular Return Measurement Unit (MRMU). At 250 km, the neutral mass spectrometer indicated a total neon return flux of .0246 times the emitted flux. The calculated fraction was .0123, including .00354 for the ambient scatter and .00354 for the altitude independent self-scatter. The pressure gages indicated return pressure less than .000933Pa .000007 at altitudes from 161 to 210 km. The maximum return pressure for 161-km orbit was calculated as 7.3 x 10-7 including a self scattering contribution of .000024 Pa .000000018.