What is the Clementine Space Probe? Discovering Water on the Moon's Surface

The Deep Space Program Science Experiment, also known as the Clementine Space Probe, was a mid-1990s mission designed to explore the Moon and test long term space exposure to newly-built equipment. A secondary objective, uncompleted due to malfunctions, was a study of near-Earth asteroid 1620 Geographos. The project was overseen as a joint project between NASA and the Ballistic Missile Defense Organization.

The Clementine Space Probe was designed to take pictures and analyze different features of the Moon's surface. To accomplish this mission, a number of different imaging instruments and lasers were placed aboard. The major success of the mission was the possible identification of water on the lunar surface near the poles. However, while NASA announced this possibility in 1998, the testing conducted was under scrutiny by many in the scientific community. It wasn't until the Chandrayaan-1 mission from the Indian Space Research Organization and the Lunar Crater Observation and Sensing Satellite from NASA in 2009 that confirmation of water was made.

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The Clementine Space Probe was designed as an octagon and measured roughly 6 feet (1.88 m) tall and 3.75 feet (1.14 m) wide. At one end of the probe was a large dish antenna and the other contained the thruster that helped the spacecraft maneuver. NASA chose to use a monopropellant hydrazine for maintaining attitude control and a bipropellant of nitrogen tetroxide and monomethyl hydrazine for general maneuvers. It was powered by solar energy that continuously charged a battery. The computer system featured a 32-bit processor that could store information on a two gigabyte solid state hard drive.

Above left: Clementine Space Probe. (Supplied by NASA; Public Domain; http://upload.wikimedia.org/wikipedia/commons/a/a2/Clementine_lunar.jpg)

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NASA launched the Clementine Space Probe from Vandenberg Air Force Base on January 25, 1994 using a Titan II rocket. For one month, the probe conducted Earth flybys before finally being inserted into lunar orbit. During its mission, it conducted a series of experiments and research projects using the various equipment on board. A charged particle telescope measured the Moon's protons and electrons to look for flux and spectra. The main camera used ultraviolet and visible light to study five different wavelengths. A secondary camera, using high-resolution photography, took pictures of the Moon's surface for later research.

After two months, the Clementine Space Probe left orbit with the intent of repeating many of the experiments on the Geographos asteroid. However, on May 7 the probe attempted an Earth flyby when it malfunctioned. One of the control thrusters fired for a duration of 11 minutes, causing the spacecraft to loose control and begin spinning. The fuel was spent during the malfunction, effectively ending the mission. Despite this, it wasn't until June that the power levels dropped below sustainability and NASA lost contact.

Above right: Clementine Deployed. (Supplied by NASA; Public Domain; http://upload.wikimedia.org/wikipedia/commons/3/35/Clementine_Deployed.gif)

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While in lunar orbit, the mission controllers developed an impromptu experiment that utilized the probe's radio transmitters to gather more information. Known as the “Bistatic Radar Experiment,” the spacecraft's transmitter was directed at the polar caps of the Moon. As the signals reflected off the poles, they were picked up by the Deep Space Network of receivers on Earth. Analysis of the experiment led NASA to believe that water ice existed in these regions. A similar experiment was conducted, however, by the Arecibo radio telescope from Earth. This study did not obtain the same results and dispelled the theory that there was water on the Moon until 2009, when it was a primary focus of new missions.

Above left: South Pole of the Moon. (Supplied by NASA; Public Domain; http://upload.wikimedia.org/wikipedia/commons/0/0e/Moon_PIA00001_modest.jpg)

NASA: http://setas-www.larc.nasa.gov/CLEM/dspse.html

Space Policy Project: http://www.fas.org/spp/starwars/program/clem.htm