Lunar Reconnaissance Orbiter
2009-present
The Moon-mapping orbiter that has been photographing the lunar surface since 18 June 2009 - still operational.
Specs
1,916 kg; ~50 km orbit; mapped >99% of the lunar surface; found water ice in permanently shadowed craters.
Why it matters
It has photographed the Apollo landing sites in detail - the landers, the rovers, even the astronauts' footprints. Independent, ongoing confirmation of where the hardware really is.