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Clementine (officially called the Deep Space Program Science Experiment (DSPSE)) was a joint space project between the Ballistic Missile Defense Organization (previously the Strategic Defense Initiative Organization) and NASA, launched on January 25, 1994. Its objective was to test sensors and spacecraft components in long-term exposure to space and to make scientific observations of both the Moon and the near-Earth asteroid 1620 Geographos.
Its lunar observations included imaging at various wavelengths in the visible as well as in ultraviolet and infrared, laser ranging altimetry, gravimetry, and charged particle measurements. These observations were for the purposes of obtaining multi-spectral imaging of the entire lunar surface, assessing the surface mineralogy of the Moon, obtaining altimetry from 60°N to 60°S latitude, and obtaining gravity data for the near side. There were also plans to image and determine the size, shape, rotational characteristics, surface properties, and cratering statistics of Geographos. However, observation of the asteroid was not made due to a malfunction in the spacecraft.
Spacecraft design
thumb|3D model of Clementine
The spacecraft was an octagonal prism 1.88 m high and 1.14 m across, with two solar panels protruding on opposite sides parallel to the axis of the prism. A high-gain fixed dish antenna was at one end of the prism, and the 489 N thruster at the other end. The spacecraft was three-axis stabilized in lunar orbit via reaction wheels with a precision of 0.05 deg in control and 0.03 deg in knowledge. An image compression system was provided by the French space agency CNES.
Mission
thumb|left|200px|Clementine launch
thumb |right |Animation of Clementines trajectory around the [[Moon from February 19, 1994 to May 3, 1994<br />]]
On January 25, 1994, Clementine was launched from Space Launch Complex 4 West at Vandenberg Air Force Base, California, using a Titan II launch vehicle. The mission had two phases. After two Earth flybys, lunar insertion was achieved approximately one month after launch. Lunar mapping took place over approximately two months, in two parts. The first part consisted of a five-hour elliptical polar orbit with a periapsis of about 400 km at 13 degrees south latitude and an apoapsis of 8,300 km. Each orbit consisted of an 80-minute lunar mapping phase near periapsis and 139 minutes of downlink at apoapsis.
After one month of mapping the orbit was rotated to a periapsis at 13 degrees north latitude, where it remained for one more month. This allowed global imaging and altimetry coverage from 60° south to 60° north, over a total of 300 orbits.
After a Moon to Earth transfer and two more Earth flybys, the spacecraft was to head for 1620 Geographos, arriving three months later for a flyby, with a nominal approach closer than 100 km. Unfortunately, on May 7, 1994, after the first Earth transfer orbit, a malfunction aboard the craft caused one of the attitude control thrusters to fire for 11 minutes, using up its fuel supply and causing Clementine to spin at about 80 rpm. Under these conditions, the asteroid flyby could not yield useful results, so the spacecraft was put into a geocentric orbit passing through the Van Allen radiation belts to test the various components on board.
The mission ended in June 1994 when the power level onboard dropped to a point where the telemetry from the spacecraft was no longer intelligible. However, "because the spacecraft was fortuitously in the correct attitude to power up again, ground controllers were able to briefly regain contact between 20 February and 10 May 1995".
Partial failure and fate
thumb|Clementine at the Smithsonian Air and Space Museum
On May 7, 1994 (UTC), Clementine experienced a computer failure after it left Lunar orbit. The failure caused it to use up its remaining propellant, spinning the spacecraft up to 80 rotations per minute. It was utilized in a geocentric orbit until the end of its mission, but the asteroid trip was aborted.
Artifacts
The engineering model of the Clementine spacecraft hangs in the National Air and Space Museum in Washington, D.C.
See also
- List of missions to the Moon