Purging sensitive science instruments with nitrogen in the STS environment

Potential contamination of extremely sensitive science instruments during prelaunch, launch, and earth orbit operations are a major concern to the Galileo and International Solar Polar Mission (ISPM) Programs. The Galileo Program is developing a system to purify Shuttle supplied nitrogen gas for in-flight purging of seven imaging and non-imaging science instruments. Monolayers of contamination deposited on critical surfaces can degrade some instrument sensitivities as much as fifty percent. The purging system provides a reliable supply of filtered and fried nitrogen gas during these critical phases of the mission when the contamination potential is highest. The Galileo and ISPM Programs are including the system as Airborne Support Equipment (ASE).