Gamma Ray and Neutron Detector (GRaND) is the scientific instrument carried by Dawn spacecraft to measure the elemental composition of both Vesta and Ceres. It uses a total of 21 sensors with a very wide field of view to measure the energy from gamma rays and neutrons that either bounce off or are emitted by a celestial body, revealing many of the important atomic constituents of the its surface down to a depth of 3 feet (1 meter).  
The instrument is provided by Los Alamos National Labs and operated by the Planetary Science Institute.
NASA/JPL-Caltech
2007
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