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Clementine - Lunar Mission

From Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24, for About.com

Clementine Lunar Mission

Clementine Lunar Mission

NASA
  • Nation: U.S. (66)
  • Objective(s): lunar orbit
  • Spacecraft: Clementine
  • Spacecraft Mass: 424 kg
  • Mission Design and Management: BMDO and NASA
  • Launch Vehicle: Titan IIG (no. 23G-11)
  • Launch Date and Time: 25 January 1994 / 16:34 UT
  • Launch Site: WSMC / SLC-4W
Clementine Scientific Instruments:
  1. ultraviolet/visible camera
  2. near-infrared camera
  3. long-wave infrared camera
  4. high-resolution camera
  5. two star tracker cameras
  6. laser altimeter
  7. bistatic radar experiment
  8. gravity experiment
  9. charged-particle telescope
Results: Clementine was the first U.S. spacecraft launched to the Moon in over twenty years (since Explorer 49 in June 1973).

The Clementine spacecraft, also known as the Deep Space Program Science Experiment (DSPSE), was designed and built to demonstrate a set of lightweight technologies such as small imaging sensors for future low-cost missions flown by the Department of Defense. Clementine carried fifteen advanced flight-test components and ten science instruments.

After launch, the Clementine spacecraft remained in a temporary orbit until 3 February 1994, at which time a solid-propellant rocket ignited to send the vehicle to the Moon. After two subsequent Earth flybys on 5 February and 15 February, Clementine successfully entered an elliptical polar orbit on 19 February with a period of 5 days and a perilune of 400 kilometers.
In the following two months, Clementine transmitted about 1.6 million digital images of the lunar surface; in the process, it provided scientists with their first look at the total lunar landscape, including polar regions.
After completing its mission goals over 297 orbits around lunar orbit, controllers fired Clementine’s thrusters on 3 May to inject it on a rendezvous trajectory in August 1994 with the asteroid 1620 Geographos. Due to a computer problem at 14:39 UT on 7 May that caused a thruster to fire and use up all propellant, the spacecraft was put into an uncontrollable tumble at about 80 rpm with no spin control. Controllers were forced to cancel the asteroid flyby and return the vehicle to the vicinity of Earth. A power supply problem on 20 July further diminished the operating capacity of the vehicle.

Eventually, lunar gravity took control of Clementine and propelled it into heliocentric orbit. The mission was terminated in June 1994 when falling power supply levels no longer allowed clear telemetry exchange. On 3 December 1996, DoD announced that Clementine data indicated that there was ice in the bottom of a permanently shadowed crater on the lunar south pole.

Scientists estimated the deposit to be approximately 60,000 to 120,000 cubic meters in volume— comparable to a small lake that is 4 football fields in surface area and 5 meters deep. This estimate was very uncertain, however, due to the nature of the data.

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