Clementine, or the USA's Return to the Moon
Clementine was the first U.S. moon mission since the Apollo program. And the moon was more than ready for a follow-up. After all, what goes on below the surface? The deepest core sample was just 3 meters deep. Noninvasive methods exist, but they require proximity and lots of different wavelengths. Also, a general temperature map existed, but the resolution was very poor, just like the topology of the surface of the moon. It was time to find out more details about the moon (Burnham 34, 37-8).
This mission would not have gotten off the ground without NASA teaming up with the Department of Defense. They joined the project with the intention of testing some missile detector sensors, the durability of surveillance technology, and other technology which would have been a violation of the Antiballistic Missile Treaty had they been used on a manmade object. For NASA, they would get the chance to map the moon’s surface as well as visit an asteroid (which did not pan out, as we shall see later on), plus the costs would be greatly reduced (Burnham 34-5, Talcott 43).
The Ballistic Missile Defense Organization, or the engineers behind the proposed “Star Wars” missile defense system, was tasked with retrofitting a rocket to purpose Clementine. The actual probe was built by the Naval Research Laboratory. As far as the hardware of the probe was concerned, the military was able to meet most of the scientists’ requests for instruments including
- a laser imaging and ranging (LIDAR) CCD to map the surface to a resolution of 10-30 meters
- a UV/Visible wavelength CCD with an average resolution of 125 by 325 meters
- an infrared camera for temperature readings
- an ion detector
However, a few cuts had to be made if the military was going to get their money’s worth out of the mission. The Laurence Livermore National Laboratory was put in charge of conducting the missile testing while the Goddard Space Flight Center charted the course of the mission and had JPL gather data (Burnham 35-6).
Altogether, the probe was ready to launch just two years after planning started, a very fast turnaround. At the time, the cost was $75 million (over $125 million in 2015 dollars, still a bargain). Yes, some older technology was used but it was more than capable and helped reduce the cost of the mission. On January 25, 1994, Clementine was launched on a Titan II G rocket that had spent the past 25 years sitting in an Aransas ICBM silo before being repurposed. Now that is recycling! (34)
Amazingly, the 71-day mission ended on May 3, 1994. By this time, over 2 million images were taken of the Moon’s surface, 38 million square kilometers catalogued, and the rarely imaged South Pole-Aitken Basin was heavily studied. Over 10,000 of the images were high res with some showing details as small as 10 meters. Thanks to gravity readings, a better idea of the crust distribution was established and theories about thinner portions occurring near the floor of basins were confirmed. And to top that off the 11 wavelength filters that came equipped with the two cameras were able to look at wavelengths from 490 nanometers to 1900 nanometers (from visible to infrared), giving scientists a great view into the chemical makeup of the moon’s surface. A majority of the surface seems to be covered in plagioclase, pyroxene, and olivine with the northern hemisphere being a good mix of them all. Below the crust appears to be the remnants of the lunar surface reheating based on the levels of pure anorthosite found, which only forms under such conditions (Spudis, Talcott 43-4).
Of course, the biggest find of Clementine was found at the poles of the moon. Around them, where temperatures can get as low as -233 degrees Celsius, the probe found traces of “enhanced circular polarization ratio” (CPR) which is normally a great indicator for water ice. This data was obtained by firing the transmitter of Clementine into the perpetually darkened craters near the poles of the moon and recording the reflection. However, rocky terrain could also give off the same readings and so it took much more analysis for the science teams to definitely say that it indeed was water ice causing the readings. While Clementine looked at the south pole, a 300 kilometer crater was discovered and the South-Pole-Aitken Basin was studied in more detail and this found to be 2,500 kilometers in diameter and 12 kilometers deep. This makes it the largest impact crater in the south pole (Spudis, Talcott 45-6).
The 71 day mission was not the only planned activity for Clementine. After its moon mission, engineers had it set a course to visit 1620 Geographos in August of 1994. But while en route, an error occurred that caused the probe to burn all its remaining fuel and fall far off course, lost to the ravages of space. Somewhere out there, it still roams... (Talcott 47)
Burnham, Robert. “The Moon Miner’s Daughter.” Astronomy Feb. 1994: 34-8. Print.
Spudis, Paul. “Clementine – The Legacy, Twenty Years On.” Airspacemag.com. Air and Space Magazine, 21 Jan. 2014. Web. 09 Oct. 2015.
Talcott, Richard. "The Moon Comes into Focus." Astronomy Sept. 1994: 43-7. Print.
© 2015 Leonard Kelley