The Lunar Prospector is designed for a low-polar orbit investigation of the Moon, including mapping of surface composition and possible polar ice deposits, measurements of magnetic and gravity fields, and study of lunar outgassing events. Data from the 1- to 3-year mission will allow construction of a detailed map of the surface composition of the Moon, and will improve our understanding of the origin, evolution, current state, and resources of the Moon. The spacecraft is scheduled for launch in October 1997.
The spacecraft will be a graphite-epoxy drum, 1.4 meters in diameter and 1.22 meters high with three radial instrument booms. It will be spin-stabilized and controlled by 6 hydrazine monopropellant 22-Newton thrusters. Communications are through two S-band transponders and a slotted, phased-array medium gain antenna and omnidirectional low-gain antenna. There will be no on-board computer, ground command will be through a 3.6 kbps telemetry link. Total mission cost will be $51 million (in 1992 dollars). After launch, the Lunar Prospector will have a 110 hour cruise to the Moon, followed by insertion into a 100 kilometer altitude circular lunar polar orbit with a period of 118 minutes.
The gamma ray spectrometer and the neutron spectrometer will return global data on elemental abundances, which will be used to help understand the evolution of the lunar highland crust and the duration and extent of basaltic volcanism, and to assess lunar resources. The neutron spectrometer will also locate any significant quantities of water ice which may exist in the permanently shadowed areas near the lunar poles.
The magnetometer/electron reflectometer experiments will return data on the lunar crustal magnetic field and the lunar induced magnetic dipole. These data will help provide an understanding of the origin of lunar paleomagnetism and the degree to which impacts can produce paleomagnetism, and allow constraints on the size and composition of the (possible) lunar core.
The alpha particle spectrometer instrument will be used to find radon outgassing events on the lunar surface by detecting alpha particles from the radon gas itself and its decay product, polonium. Observations of the frequency and locations of the gas release events will help characterize one possible source of the tenuous lunar atmosphere. Determination of the relationship of outgassing sites with crater age and tectonic features may be possible. This may in turn be used to characterize the current level of lunar tectonic activity.
The Doppler gravity experiment will use Doppler tracking of S-Band radio signals to characterize the spacecraft orbit and determine the lunar gravity field. These data will provide information on the lunar interior and, combined with lunar topographic data, will allow modelling of the global crustal asymmetry, crustal structure, and subsurface basin structure. The data can also be used for planning future lunar missions.
The Lunar Prospector mission has been selected by NASA for full development and construction as part of NASA's Discovery program. This program funds spacecraft that can be developed in less than three years for under $150 million.