The NEAR XRS is part of the X-Ray/Gamma-Ray Spectrometer (XGRS) suite on the NEAR mission.  It is 
 an X-ray resonance fluorescence spectrometer that detects the characteristic X-ray line emissions 
 excited by solar X-rays from major elements in the asteroid's surface. It covers X-rays in the 
 energy range from 1 to 10 keV using three gas proportional counters.  The balanced, differential 
 filter technique is used to separate the closely spaced Mg, Al, and Si lines lying below 2 keV. The 
 gas proportional counters directly resolve higher energy line emissions from Ca and Fe. A mechanical     
 collimator gives the XRS a 5 deg FOV, with which it will map the chemical composition of the asteroid 
 at spatial resolutions as great as 2 km in the low orbits. It also includes a separate solar monitor 
 system to measure continuously the incident spectrum of solar X-rays, using both a gas proportional 
 counter and a high-spectral-resolution silicon X-ray detector. The XRS performs in-flight calibration 
 using a calibration rod with Fe-55 sources that can be rotated into or out of the detector FOV.