Lunar Prospector was the third mission selected by NASA for full development and construction as part of the Discovery Program. At a cost of $62. 8 million, the 19-month mission was put into a low polar orbit of the Moon, accomplishing mapping of surface composition and possible polar ice deposits, measurements of magnetic and gravity fields, and study of lunar outgassing events. Based on Lunar Prospector Neutron Spectrometer (NS) data, mission scientists have determined that there is indeed water ice in the polar craters of the Moon. The mission ended July 31, 1999, when the orbiter was guided to an impact into a crater near the lunar south pole in an (unsuccessful) attempt to analyze lunar polar water by vaporizing it to allow spectroscopic characterization from Earth telescopes.