Lunar Prospector was the third mission selected by NASA for full development and construction as part of the Discovery Program. The 19-month mission was designed for a low polar orbit investigation of the Moon, including mapping of surface composition including polar ice deposits, measurements of magnetic and gravity fields, and study of lunar outgassing events. The mission ended July 31, 1999, when the orbiter was deliberately crashed into a crater near the lunar south pole, after the presence of water ice was successfully detected.