Regolith X-Ray Imaging Spectrometer (REXIS) Aboard the OSIRIS-REx Asteroid Sample Return Mission

The Regolith X-ray Imaging Spectrometer (REXIS) is the student collaboration experiment proposed and built by an MIT-Harvard team, launched aboard NASA’s OSIRIS-REx asteroid sample return mission. REXIS complements the scientific investigations of other OSIRIS-REx instruments by determining the relative abundances of key elements present on the asteroid’s surface by measuring the X-ray fluorescence spectrum (stimulated by the natural solar X-ray flux) over the range of energies 0.5 to 7 keV. REXIS consists of two components: a main imaging spectrometer with a coded aperture mask and a separate solar X-ray monitor to account for the Sun’s variability. In addition to element abundance ratios (relative to Si) pinpointing the asteroid’s most likely meteorite association, REXIS also maps elemental abundance variability across the asteroid’s surface using the asteroid’s rotation as well as the spacecraft’s orbital motion. Image reconstruction at the highest resolution is facilitated by the coded aperture mask. Through this operation, REXIS will be the first application of X-ray coded aperture imaging to planetary surface mapping, making this student-built instrument a pathfinder toward future planetary exploration. To date, 60 students at the undergraduate and graduate levels have been involved with the REXIS project, with the hands-on experience translating to a dozen Master’s and Ph.D. theses and other student publications.     

Stereographic Projection in the National Airspace System

Consideration is given to the calculation of stereographic representations of airborne targets from observations of slant range, azimuth, amd altitude in a multiple radar tracking system. Emphasis is placed upon the translation of the accuracy of the surveillance information into the stereographic plane. Applications include air traffic control operations in which calculations must be performed repeatedly in real time for numerous targets without overtaxing available computational resources.     

Approximation of Corrected Slant Range in a Radar Surveillance System

Consideration is given to numerical procedures for evaluating the corrected slant range in a radar surveillance system. Applications include air traffic control operations in which such calculations must be performed repeatedly in real time for a multitude of targets without overtaxing available computational resources.