Spacecraft above the Moon.

Artist's conception, Lunar Prospector spacecraft just before impact on Moon.

Goals: Lunar Prospector was designed to provide answers to long-standing questions about the Moon, its resources, its structure and its origins.

Accomplishments: For a year and a half its five instruments mapped lunar resources, gravity and magnetic fields, and even outgassing events. After a year and a half of ground-breaking science, Lunar Prospector took a bold step towards furthering its science legacy by intentionally impacting a targeted south polar crater of the Moon, in the hopes that ejecta from the impact could be seen from Earth and analyzed for the existence of water ice.

6 Jan 1998: Launch
11 Jan 1998: Arrival at Moon
31 Jul 1999: Moon Impact

Mission Type: Orbiter
Launch Vehicle: Athena-2 (LM-004)
Launch Site: WSMC / SLC-46
NASA Center: Ames Research Center
Spacecraft Mass: 300 kg
Spacecraft Instruments:
1) MAG magnetometer
2) ER electron reflectometer
3) GRS gamma-ray spectrometer
4) NS neutron spectrometer
5) APS alpha particle spectrometer
6) DGE Doppler gravity experiment (using S-band antenna)
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24

Lunar Prospector was designed to create the first complete compositional and gravity maps of the Moon during its one-year mission. This mission was the first competitively selected and the third to launch in a series of missions in NASA's Discovery program. This program was developed to produce frequent, low-cost missions to explore the solar system.

Lunar Prospector was a simple and reliable spin-stabilized spacecraft. It rotated around its own central axis in order to control its orientation en route to the Moon. Prospector was small -- when full of fuel, the spacecraft weighed only 295 kg (650 lb). That's about a quarter as heavy as an average-sized car!

After two midcourse corrections, Lunar Prospector entered orbit around the Moon 105 hours after launch. Initial parameters were 92 x 153 km. After two further corrections on 13 and 15 January, the spacecraft entered its operational 100- x 100-km orbit at 90ý inclination.

Perhaps of most interest to scientists was continued investigation into the signs of water ice on the Moon as found by the Clementine probe. Lunar Prospector's data showed an estimated six billion tons of water ice trapped in the shadows of the lunar polar regions. The spacecraft also detected strong localized magnetic fields; mapped the global distribution of major rock types; and discovered signs of a tiny, iron-rich core.

On 10 December 1998, Lunar Prospector's orbit was lowered to 40 km to perform high resolution studies. A subsequent maneuver on 28 January 1999 changed the orbit to 15 x 45 km and ended the space probe's primary mission.

Lunar Prospector was deliberately landed on a shadowed crater on the lunar surface at 09:52:02 UT on 31 July 1999. During the descent, the spacecraft failed to find any observable signature of water. The vehicle carried the cremated remains of geologist Eugene Shoemaker to the lunar surface.

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