urn:nasa:pds:context:instrument:xrs.mess 1.1 1.10.1.0 Product_Context 2016-10-01 1.0 extracted metadata from PDS3 catalog and modified to comply with PDS4 Information Model 2018-06-05 1.1 Minor updates to support PDS3 to PDS4 migrations. Added DOI for reference, removed optional attributes with N/A as values, added intstrument subtype, and did minor edits to the description field. urn:nasa:pds:context:instrument_host:spacecraft.mess instrument_to_instrument_host https://doi.org/10.1007/s11214-007-9248-5 Schlemm, C.E., II, R.D. Starr, G.C. Ho, K.E. Bechtold, S.A. Benedict, J.D. Boldt, W.V. Boynton, W. Bradley, M.E. Fraeman, R.E. Gold, J.O. Goldsten, J.R. Hayes, S.E. Jaskulek, E. Rossano, R.A. Rumpf, E.D. Schaefer, K. Strohbehn, R.G. Shelton, R.E. Thompson, J.I. Trombka, and B.D. Williams, The X-Ray Spectrometer on the MESSENGER spacecraft, Space Science Reviews, 131, 393-415, 2007. X-Ray Spectrometer Spectrometer X-Ray Spectrometer The X-Ray Spectrometer (XRS) experiment was comprised of three identical gas proportional counters (GPC) that measure X-rays emitted from the surface of Mercury in the energy range from about 1 to 10 keV. X-rays in this energy range sample the planetary surface to depths of a few tens of microns. The GPCs each had a 10-cm2 active area and used both anti-coincidence wires and pulse shape discrimination to minimize background. Balanced filters were used to resolve the lower energy X-ray lines from Mg, Al, and Si. This technique was used previously on other orbital X-ray experiments flown on the Apollo 15, 16 and NEAR-Shoemaker missions. One GPC had a thin aluminum filter, which filtered out Si photons, one had a thin Mg filter, which filtered out Al and Si photons, and the third GPC had no filter. The energy resolution of the gas counters was sufficient to resolve higher energy lines from S, Ca, Ti, and Fe. A small Si-PIN detector was used as a solar monitor, because the Sun is the source of the planetary X-ray fluorescence.