a U.S. spacecraft that is designed to map the surface of the moon and to help select ideal sites for unmanned and eventually manned lunar landers. It is scheduled to launch on April 24, 2009, from Cape Canaveral, Fla., on an Atlas (Atlas rocket) rocket that also will launch the Lunar Crater Observation and Sensing Satellite, which is designed to seek water at the lunar south pole. The transfer from Earth orbit to lunar orbit will take four days. LRO will be placed in an elliptical, polar commissioning orbit for up to 60 days and then use onboard thrusters to lower its orbit to a height of 50 km (30 miles) for one year of operations. An extended five-year mission at a higher altitude orbit may be added.

The U.S. National Aeronautics and Space Administration has given highest priority to characterization of the radiation environment in lunar orbit since this will be a major health consideration for space crews on future missions of the manned Constellation program. To that end, the Cosmic Ray Telescope for the Effects of Radiation will carry two special silicon and plastic detectors, one aimed toward the lunar surface and the other spaceward. These detectors are designed to absorb radiation in the same way as human bone and muscle tissue.

The Lunar Reconnaissance Orbiter Camera will map most of the surface (including regions covered by Apollo (Apollo program) and other missions) in order to determine crater formation rates and hazards as well as smaller features that may be hazardous to spacecraft landing on the Moon. Sites suitable for in situ resource utilization have the highest importance. Data from the Lunar Orbiter Laser Altimeter will be used to produce topographic maps with a vertical accuracy of 1 metre (3 feet).

The search for water that can be used by future lunar bases will be aided by three instruments. The Lyman-Alpha Mapper will looking for the ultraviolet (ultraviolet radiation) glow specific to hydrogen in permanently shadowed regions. The Diviner Lunar Radiometer will chart how surface materials heat and cool during lunar day and night, and the Lunar Exploration Neutron Detector will measure neutrons (neutron) scattered back to space by hydrogen nuclei (nucleus).