Contamination Control Modeling for Europa Clipper’s MASPEX Instrument Aperture Cover Deployment

MASPEX (Mass Spectrometer for Planetary Exploration/Europa) is a mass spectrometer flying aboard the Europa Clipper mission to identify gases in the Europa exosphere. As a mass spectrometer looking for trace species, the instrument is highly sensitive to outgassing contamination. A single monolayer of a species of interest collected on MASPEX may impact the science measurement. MASPEX has a one-time deployable vacuum sealed door to protect it from outgassing contamination. The initial plan was to deploy the door after Jupiter Orbit Insertion (JOI), however it was proposed that the door open earlier in cruise to accommodate concerns about the door deployment mechanism operating at cold temperatures. As part of the assessment to determine if the aperture cover door could be opened early, the Contamination Control Engineering group at the NASA Jet Propulsion Laboratory was tasked with assessing the contamination levels expected to make it into the MASPEX inlet. The main contamination environments for MASPEX during cruise and JOI are outgassing and propellant droplets. Outgassing follows three transport mechanisms to deposit on sensitive surfaces; direct line of sight, reflected, and return flux. The JPL Contamination Control team evaluated the contamination environments and mechanisms and found that the primary vector for contamination to reach MASPEX on Europa Clipper is reflected flux. This presentation discusses the modeling approach used to predict outgassing deposition on MASPEX resulting from opening the aperture cover door earlier in cruise. The focus is on the impact of the thermal environment on spacecraft outgassing, the extended duration over which contamination accumulation can occur, and the orientation of the solar array inducing a reflective path for outgassing.