The Apollo X-Ray Fluorescence Spectrometer

Located in the Science Instrument Module of Apollo 15 and 16, the X-ray Fluorescence Spectrometer measured the X-ray fluorescence induced in the lunar surface by the incident solar flux. The fluorescing radiation energy spectra is characteristic of the elemental composition of the lunar surface allowing qualitative and quantitative assessments of the lunar surface. This paper provides a description of the detectors, circuit functions, on-board data processing techniques, in-flight calibration, hardware and flight results of the spectrometer.