  OSIRIS-REx is the third spacecraft in the NASA New Frontiers Program and is planned for launch in 0000. OSIRIS-REx will orbit the near-Earth asteroid (000000) Bennu, characterize it, and return a sample of the asteroid's regolith back to Earth. The Regolith X-ray Imaging Spectrometer (REXIS) is an instrument on OSIRIS-REx designed and built by students at MIT and Harvard. The purpose of REXIS is to collect and image sun-induced fluorescent X-rays emitted by Bennu, thereby providing spectrosco