Gamma Ray Spectrometer (2001 Mars Odyssey)

The Gamma Ray Spectrometer (GRS) is a gamma-ray spectrometer on the 2001 Mars Odyssey spacecraft, a space probe orbiting the planet Mars since 2001.

Part of NASA's Mars Surveyor 2001 program, it returns geological data about Mars's surface such as identifying elements and the location of water.

It is maintained by the Lunar and Planetary Laboratory at the University of Arizona in the United States.

[1] The Gamma Ray Spectrometer weighs 30.5 kilograms (67 lb) and uses 32 watts of power.

The detector is a photodiode made of a 1.2-kilogram (2.6 lb) germanium crystal, reverse biased to about 3 kilovolts, mounted at the end of a 6-metre (20 ft) boom to minimize interferences from the gamma radiation produced by the spacecraft itself.

A diagram of the scientific instruments present on 2001 Mars Odyssey; the Gamma Ray Spectrometer consists of the Gamma Sensor Head, the Neutron Spectrometer and HEND (High Energy Neutron Detector).
How GRS collects data from surface