 Complete the following phrase:  He has been on six treks to Mount Everest as expedition doctor and climber; four were with the National Geographic Society deploying laser telescopes and global positioning satellite receivers to measure the exact height of Everest as well as the tectonic motion of the Asian continental plate. On two other expeditions to Everest, he served as Chief High Altitude Physician for NASA-sponsored research on human physiological responses to extreme altitude, and monitored remote body sensors worn by climbers to provide real-time medical data as they ascended the mountain. Dr. Kamler himself has climbed to within 900 vertical feet of the summit of Everest and claims to have been the only doctor high on the mountain, during the infamous 