Model to Estimate the Flux of Background Particles Expected to Accumulate on theCollector Foils of the Interstellar Gas Experiment on the Long Duration Exposure Facility Spacecraft

摘要

The Interstellar Gas Experiment (IGE) on board the Long Duration ExposureFacility (LDEF) exposed metallic foils to the interstellar wind to collect noble gas particles from outside of the solar system. The terrestrial helium present in the atmosphere at low Earth orbit altitudes was also collected on the foils, along with the interstellar helium particles. In order to discriminate between the desired interstellar helium and the background terrestrial helium particles, an analysis of the expected distribution of atmospheric helium on the foils was conducted. This analysis used the principles of the kinetic theory of gases to simulate the state of the thermosphere for the entire 69-month flight of LDEF. The key parameters needed to apply the kinetic theory of gases were the temperature and density of the helium at LDEF altitude. This information was calculated using the Mass Spectrometer and Incoherent Scatter (MSIS) model. The entire duration of the flight was split into 70 month-long intervals. For each of these intervals, mean values for the kinetic temperature and helium density were calculated. (Author)