Angular Response Characterization of the REXIS Solar X-ray Monitor (SXM)
The OSIRIS-REx spacecraft, launched on September 2016, is a NASA asteroid sample return mission to classify the near-Earth asteroid 101955 Bennu among the different meteorite groups. As part of the Regolith X-ray Imaging Spectrometer (REXIS), built by students in MIT and Harvard, the Solar X-ray Monitor (SXM), mounted on the Sun-facing side of the spacecraft, will measure the Solar X-rays incident to both Bennu and the OSIRIS-REx spacecraft. In conjunction with the data collected by REXIS’s primary spectrometer, the information provided by the SXM measurements will help reconstruct the elemental abundance of the asteroid.
The work presented here is the analysis and characterization of data taken from angular response measurements made with the SXM flight spare model, utilizing a 55Fe radiation source. From the data, plots of the count rate variability and off-axis response along the SXM FoV were made. In addition, individual measurements of the angular response tests were grouped according to their integration time and examined for variations in energy resolution and signal-to-noise ratio for the 5.9 keV and 6.5 keV iron emission lines. The goal of this project is to provide useful information that will help the calibration of the SXM on the OSIRIS-REx spacecraft for the fitting of the Solar spectra.