Apollo Lunar Traverse Gravimeter Experiment (TGE)

Gold plated unit with a rotating carrying handle at the top, which was also used for locking the unit on the Lunar Rover.

Built by the Instrumentation Laboratory at MIT, the purpose of the gravimeter was to measure the moon’s gravitational field using a precise Vibrating String Accelerometer (VSA). The central sphere is the gimbal which housed the VSA sensor. While on the Moon, astronauts would drive the device to different locations and take readings of the gravitational force. Packaged as part of Apollo 17’s ALSEP package, the gravimeter was housed on the geopallet of the lunar rover. The TGE had a nine-digit display to read out gravity and internal temperature.

Only three other gravimeters are in existence, one left on the lunar surface by Apollo 17, the mission’s back-up at the Smithsonian, and one other at Columbia University. Here is a video clip of it on a rotating stand from the 2013 auction.

Details from NASA: ”The primary sensor which formed the heart of the system was a Bosch Arma D4E Vibrating String Accelerometer (VSA), which consisted of a pair of strings mounted inside an apparatus which very precisely measured their vibrations when an electric current was passed through them. The VSA assembly was in turn mounted inside a two-axis gimbal system which served to level the system inside the TGE housing before the measurements were taken.

The system was simple to use and operate by the crew. It could be operated both on and off the back of the LRV. First, the crewman ensured that the system was level within 15 degrees of vertical. He then pushed the “GRAV” button on the front of the housing. After approximately three minutes, during which time the system was required to be undisturbed, a nine-digit readout would appear on the display panel. These numbers were then read down to the ground by the crewmen. Another pushbutton, labeled “READ” was on the front face of the housing. It allowed the crewmen to read the display after it went out, as it was designed to remain illuminated for only 20 seconds, to conserve battery power. The third button was labeled “BIAS” which was used to obtain calibration readings when the system was “inverted”.

The TGE was operated a total of 26 times during the three EVAs on Apollo 17, with excellent results. The results suggest that the basalt layer filling the valley is about a kilometer thick.”

I also have a spare Beryllium gear housing, gold-plated phase lock loop, serial numbers 010 and 011, and the plated spare battery pack assembly, serial number 010.

Part of the Future Ventures’ 🚀 Space Collection.