the island hosts one of four dedicated ground antennas that assist in the operation of the global positioning system (gps) navigation system (the others are on diego garcia (british indian ocean territory), kwajalein (marshall islands), and at cape canaveral, florida (us)). nasa and the us air force also operate a meter-class autonomous telescope (mcat) on ascension as part of the deep space surveillance system for tracking orbital debris, which can be a hazard to spacecraft and astronauts.