The Cold Cathode Gauge Experiment (CCGE) was part of the ALSEP (Apollo Lunar Surface Experiments Package) for Apollo 12, 13 & 14. Also known as the Lunar Atmosphere Experiment, the CCGE was to measure the density and temperature of the Moon’s atmosphere. This would provide infor💖mation to address questions of the lunar ambient atmosphere pressure and “the rate of decay of contaminants left in the landing area by the astronauts and the LM” (ALSEP Handbook 3.4.2). 

The Apollo 12 CCGE was combined with the Lunar Ionosphere Detector. Unfortunatel♕y, a power supply failure necessitated modification and a second attempt. Improvements were made and the CCGE was spun off as a separate unit for Apollo 13. Of course, the crew never landed on the lunar surface and that unit went unused. The Apollo 14 crew brought the improved CCGE and were finally able to successfully place the unit. They also corrected some earlier errors like initiating the instrument later to allow for dissipation of the gasses from the Lunar Module and switching the unit off during higher temperature periods. 

The present example is a flight spare, a backup for the example that flew in the Apollo 13 Lunar Module. Plans were thwarted when an oxygen tank exploded 210,000 miles from Earth and suddenly changed the mission objective from a Moon landing to survival. That flown example was never used and was destroyed in the Lunar Module when it entered Earth’s atmosꦬphere. The flight spare also includes the corresponding manual that provides all quality control testing and inspection documents for this particular unit and which includes original photographs and blueprints.