Contamination effects and analysis
Contamination from outgassing, venting, leaks and thruster firing can degrade surfaces on which contaminants deposit. The contaminant cloud can also disrupt payload operations (e.g telescopes). On-orbit contamination may modify surfaces and invalidate ground-based characterisation, e.g. charging properties measurements. High contaminant levels may also contribute to the onset of electrostatic discharge.
ESABASE/Outgassing has been developed to compute deposition on surfaces of a 3-dimensional model of a spacecraft resulting from the outgassing of other surfaces. Account is taken of direct flux, flux reflected by other surfaces, reflections from other contaminant molecules ( using a simplified cloud model), and ambient gas scattering. A temperature -dependent residence-time model is used for the outgassing. Recently, a new software tool for contamination analysis has been developed: COntamination Modelling Outgassing & Vent Analysis tool (COMOVA). It was developed by the Space Environment Department (DESP) of ONERA (physics modelling) and HTS (interfacing and pre-processing) and was funded by Space Environments and Effects Analysis Section. Contamination is a serious problem for International Space Station payloads - both contaminant deposition on experiments and contaminants in fields of view of telescopes. A tool for contaminant cloud predictions leading to a better scattering model and giving column densities and irradiances in fields of view is required.
Last update: 29 March 2007