Henize, on leave from NASA at the time, went on a hiking expedition to Mount Everest with British research group High Adventure BVI. Henize intended to test the Tissue Equivalent Proportional Counter (TEPC) at different altitudes: 17,000 ft, 19,000 ft, and 21,000 ft. The TEPC would reveal how people's bodies would be affected, including the way bodily tissues behaved, when struck by radiation, and this was important for the planning of long duration space missions. The data would be shared with NASA and BVI.