The REXIS (Regolith X-Ray Imaging Spectrometer) Student Experience: From Concept to Operation

The Regolith X-Ray Imaging Spectrometer (REXIS) is a student instrument onboard NASA’s OSIRIS-REx asteroid sample return mission. REXIS is an X-ray imaging spectrometer that uses CCDs developed at the Massachusetts Institute of Technology (MIT) Lincoln Laboratory in conjunction with a coded-aperture mask to measure the elemental abundance properties of the asteroid Bennu and map the spatial distribution of the abundances on the surface. The instrument was conceived, designed, implemented, and operated through a collaboration between MIT and Harvard College Observatory (HCO). The REXIS team, at all stages of instrument development, consisted primarily of students. MIT undergraduates developed the instrument requirements and navigated the instrument through a NASA System Requirements Review (SRR) and System Design Review (SDR) as part of the capstone class in the Aeronautics and Astronautics Department. Graduate students matured the instrument design through Preliminary Design Review (PDR) and Critical Design Review (CDR). The graduate student team consisted of three to five graduate students and was joined by undergraduate students through the MIT Undergraduate Research Opportunity Program (UROP). The graduate team continued after CDR into instrument integration and testing and ultimately delivered a fully functional flight instrument for installation on the OSIRIS-REx spacecraft in December 2015. The instrument remained healthy through launch and cruise to Bennu and completed asteroid science operations at the end of 2019. The REXIS project has engaged nearly 100 graduate and undergraduate students at MIT, Harvard, and other universities. The program has thus far resulted in twelve master’s theses and three PhD dissertations and has provided a test case for engineering research in the areas of requirements definition, model-based system engineering, and uncertainty analysis for thermal design. Students have experienced first-hand: requirements definition, instrument design, subsystem analysis, integration and testing, and interplanetary flight operations. REXIS students worked closely with subject matter experts at MIT, Harvard, MIT Lincoln Laboratory, NASA Goddard Spaceflight Center, University of Arizona, and Lockheed Martin Space Systems. Our model of student/mentor collaboration is a cornerstone of the instrument’s success that allows the project to remain flexible and robust through student transitions. In this poster, we highlight the hands-on learning and educational outcomes for the REXIS students and discuss lessons learned for future student projects.