Mission Summary
The third mission chosen for NASA's budget-friendly Discovery program, an ongoing series of competitively selected, low-cost planetary science missions. To keep costs down, engineers skipped heavy cameras entirely. Instead, they mounted five specialized instruments on three long booms extending from the spacecraft body. The probe had one clear goal: map the chemical makeup of the entire lunar surface from above.
The flight to the Moon was fast and smooth. Arriving just four days after launch, Lunar Prospector settled into a circular orbit that took it directly over the lunar north and south poles. For nineteen months, it cruised just 60 miles above the ground, later dropping down even closer to get a sharper look. Its sensors quietly read the chemical signatures of the crust, tracking magnetic fields and mapping gravity changes across the entire globe.
The big moment of the mission came when one of its instruments noticed a strange dip in radiation reflections near the poles. This measurement proved that huge amounts of hydrogen were trapped in the soil. For scientists, this was the first clear sign that billions of tons of water ice were likely mixed into the dirt inside craters that never see sunlight. Its fuel finally running low, the probe ended its journey on July 31, 1999, with a planned crash into a crater at the south pole, completing an incredibly successful mapping run.
Sources and notes can be found on the Sources page.
