These measurements were intended to provide insight into the internal structures of the Moon as it tidally deformed due interaction with the gravitational fields of the Earth and Sun.
The sensor was based on a modified LaCoste and Romberg D-meter and consisted of an adjustable mass on a sprung lever attached to the instrument's measurement electronics.
[4][5] By the time of the development of the Apollo program, it was believed only the largest objects in the universe such as stars and galaxies would generate gravitational waves of sufficient magnitude to be detectable.
[6]: 1 Following his attendance a general relativity conference at Chapel Hill in 1957, Joseph Weber started work on designing and building detectors that could experimentally prove the existence of gravitational waves.
In 1960, he published his proposal for a mechanical detector that would consist of a suspended metal cylinder that would interact with gravitational waves and produce induced vibrations that could be detected.
[9] Weber presented at a National Aeronautics and Space Administration (NASA) organised conference on relativity in 1961, highlighting that using the Moon to detect gravitational waves was an attractive option due to being seismically quieter than the Earth.
[9] The devices used for these explorations included various prototype LaCoste and Romberg type gravimeters, that allowed extremely precise measurements.
[6]: 3 In 1964, the Director of the Office of Manned Space Science, Willis Foster, proposed four geophysics teams for the Apollo lunar surface exploration program.
[19] One of the teams was dedicated to gravimetry and consisted of Joseph Weber and Gordon J. F. MacDonald, who was at that time at the University of California, Los Angeles.
[19] The team evaluated a number of proposed gravimetry experiments but despite Weber's own work on LSG prototypes starting in 1964,[14] NASA's approval of the Lunar Surface Gravimeter only came late on in the planning process for Apollo 17.
[19][21]: 12-4 The LSG's sensor was developed and built by LaCoste Romberg, and the instrument's thermal control was provided by the Arthur D. Little company.
[23] The experiment was deployed on the Moon's surface by Apollo 17 astronauts Gene Cernan and Harrison Schmitt on December 12, 1972.
[23] Following the deployment of the LSG, it was discovered that the instrument's calibration weights were not heavy enough to allow the sprung level to be properly balanced.
Adjustments were made to the sensor via remote commands by placing the weight mechanism in contact with the sprung level, applying a small amount of force.
[22] Mass values that had been calculated for the flight-like test article were used for the weights on the actual flight hardware, and subsequently only found to be incorrect after deployment during the mission.
[22] This problem was compounded by that the fact that when modifying the D-meter design for use on the Moon, a decision was taken to reduce the extent with which fine adjustments could be made since the instrument was going to be static.
[22] Apollo 17's Schmitt claimed that Weber's team had refused to test the device on a slope in a way that would emulate lunar gravity, in order to protect the proprietary nature of the instrument.
[26][27] Due to the instrument's failure, the LSG did not manage to achieve two of its primary objectives, to identify any gravitational wave–induced oscillations in the Moon and to measure the isostatic response to tidal forces from the Sun and Earth.
[29] To get the instrument to operate as a seismograph, there was a need to use the weight caging mechanism to apply a force to the sprung lever in order to balance it.
[25] The investigation suggested that combining the LSG and other Apollo seismograph data might increase the resolution and understanding of the Moon's internal structure.
[25] Whilst the LSG failed in its original objectives, the potential for the Moon as an environment conducive to the study of gravitational waves remains.