The Clementine mission and its lost asteroid

A 1994 spacecraft mapped the Moon brilliantly — then a stuck thruster ended its trip to Geographos.

Published 2026-10-23

Clementine, officially the Deep Space Program Science Experiment, was a joint project of the Ballistic Missile Defense Organization and NASA, launched on 25 January 1994.^[4]

Two targets

Its goals were to test sensors and spacecraft parts in long-term space exposure and to observe both the Moon and asteroid 1620 Geographos.^[4] At the asteroid, the plan was to measure size, shape, rotation, surface properties and craters during a flyby closer than 100 km.^[4]

A success at the Moon

At the Moon, Clementine imaged the surface in visible, ultraviolet and infrared light, used a laser altimeter and measured gravity. Over two months its camera covered the Moon completely.^[4]

What went wrong

On 7 May 1994, after leaving the Moon, a malfunction caused one attitude thruster to fire for 11 minutes, using up the fuel and spinning the spacecraft at about 80 rpm. A useful flyby was no longer possible.^[4]

What it would have seen

Its camera would have reached about 25 m per pixel at closest approach, with images about 7 × 10 km — enough to frame the whole asteroid.^[4] Instead, Goldstone radar provided the best views later that year.^[2]

Numbered citations link to the sources list on the Geographos overview page.