Mission Safety for Repair of the Alpha Magnetic Spectrometer using the Extravehicular Mobility Unit Space Suit Assembly

The Alpha Magnetic Spectrometer (AMS) installed on the International Space Station (ISS) is a particle detector uniquely positioned to advance knowledge of the Universe by determining characteristics of cosmic ray particles. AMS was installed in 2011 with an operational life expectancy of three years. The thermal control system for one of the detectors has now degraded so that only one of four cooling pumps is functioning. NASA has directed repair requiring multiple Extra-Vehicular Activities (EVA)s. AMS repair will involve crewmembers working in areas that were not intended to be accessed on-orbit. Performing off-nominal activities during EVA is not exceptional over the history of 200 plus space station EVAs, and NASA has a risk management process in place to assure mission safety.
Risks to the Extra-vehicular Mobility Unit Space Suit Assembly (SSA) have been characterized for the activities to be executed during AMS repair. Risks include potential suit puncture and abrasion due to sharp edges and debris generated during the repair. Material testing established a reasonable estimate of the worst-case debris that could damage the SSA glove. Manned glove cycle testing was then performed to formulate an engineering risk assessment and recommendation for acceptability of the glove for EVA use. This paper will discuss the AMS mission risks and the testing completed to provide rationale for acceptable risk to the SSA.