U. S. Orbital mission to Mars, part of NASA's Mars Exploration Program, launched in April, 2001 and arrived at Mars in October, 2001. The mission's goals are to map chemical elements and minerals, look for water, and analyze the low-orbit radiation environment using three primary instruments: Thermal Emission Imaging System (THEMIS), Gamma Ray Spectrometer (GRS), and Mars Radiation Environment Experiment (MARIE). During and after its science mission, the Odyssey orbiter will also support other missions in the Mars Exploration program. It is providing communications relay for U. S. And international landers, including the Mars Exploration Rovers launched in June and July, 2003. 2001 Mars Odyssey website.