Radiation-induced voltage on spacecraft internal surfaces

Abstract

The charging of surfaces of insulators beneath the thermal control blankets on spacecraft has been numerically simulated. Such insulators are found on wiring harnesses, bulkhead feed-throughs, component mounting hardware, tiewraps, thermal sensors, etc. These insulators are shielded from the low energy space plasma by the grounded solar blankets. It is determined that the surfaces of these insulators rise to many tens of kV in the Earth's electron belts unless sufficient conduction to the spacecraft frame is established. Secondary electron emission is not sufficient to hold the potential to low values. The dependence of charging upon insulator thickness, electron energy spectra, and material properties is investigated. This phenomena is posited as an explanation for the Spacecraft Anomalies seen on many spacecraft, and on the CRRES satellite in particular .

Evolution of the Electron Yield Curves of Insulators as a Function of Impinging Electron Fluence and Energy

“…These data were consistent with predictions from Cazaux [17] and Reimer [11] that steady state yields should decrease with continued incident electron irradiation due to radiation induced conductivity as well as the additional defects and electron trapping that are created by the incident beam and high internal electric fields due to internal charge build up. Furthermore, Liehr et al [41] reported similar decreases in electron yield parameters with continued electron irradiation on polyethylene, finding a decrease in E 2 by 26% after irradiating with 20 mC of incident charge. Figure 6a shows the emission spectra of a negatively biased conducting gold sample measured using a 1 keV incident beam.…”

Methods for High Resistivity Measurements Related to Spacecraft-Charging

“…We concluded then that the classical resistivity method may not be most appropriate test method for spacecraft charging problem [1,12]. The charge storage method was developed by Frederickson et al [7,8,[13][14][15][16], Levy et al [17][18][19] and others [20,21] to measure the resistivity in a more applicable configuration. In this method, charge is deposited near the surface of an insulator and allowed to migrate through the dielectric to a grounded conductor.…”

Review of an Internal Charging Code, NUMIT

“…On other occasions, Frederickson developed versions of NUMIT that have even more varied capabilities. Examples include the following: a version that can take semiisotropic [4] or isotropic electron sources [unpublished], a version that incorporates incoming electron motion in an electric field generated in dielectrics [5], a version that can take spectrum input, etc. Unfortunately, Frederickson recently passed away.…”