MMS Observatory TV Results Contamination Summary

The Magnetospheric Multiscale (MMS) mission is a constellation of 4 observatories designed to investigate the fundamental plasma physics of reconnection in the Earth's magnetosphere. The various instrument suites measure electric and magnetic fields, energetic particles, and plasma composition. Each spacecraft has undergone extensive environmental testing to prepare it for its minimum 2 year mission. In this paper, we report on the extensive thermal vacuum testing campaign. The testing was performed at the Naval Research Laboratory utilizing the "Big Blue" vacuum chamber. A total of ten thermal vacuum tests were performed, including two chamber certifications, three dry runs, and five tests of the individual MMS observatories. During the test, the observatories were enclosed in a thermal enclosure known as the "hamster cage". The enclosure allowed for a detailed thermal control of various observatory zone, but at the same time, imposed additional contamination and system performance requirements. The environment inside the enclosure and the vacuum chamber was actively monitored by several QCMs, RGA, and up to 18 ion gauges. Each spacecraft underwent a bakeout phase, which was followed by 4 thermal cycles. Unique aspects of the TV campaign included slow pump downs with a partial represses, thruster firings, Helium identification, and monitoring pressure spikes with ion gauges. Selected data from these TV tests is presented along with lessons learned.