The 2001 Mars Odyssey Orbiter is scheduled for launch on April 7, 2001. It will arrive at Mars on Oct. 20, 2001, if launched on schedule. After a propulsive maneuver into a 25-hour capture orbit, aerobraking will be used over the next 76 days to achieve the 2-hour science orbit. Aerobraking was utilized on the Mars Global Surveyor mission. The Orbiter will carry 3 science instruments, the Thermal Emission Imaging System (THEMIS), the Gamma Ray Spectrometer (GRS), and the Mars Radiation Environment Experiment (MARIE). THEMIS will map the mineralogy and morphology of the Martian surface using a high-resolution camera and a thermal infrared imaging spectrometer. The GRS will achieve global mapping of the elemental composition of the surface and determine the abundance of hydrogen in the shallow subsurface. The GRS is a rebuild of the instrument lost with the Mars Observer mission. The MARIE will characterize aspects of the near-space radiation environment as related to the radiation-related risk to human explorers.