Geodesy instrument package on the Moon for improving our knowledge of the Moon and the realization of reference frames

Abstract The use of passive Laser reflectors on the lunar surface has been the most attractive in the Apollo era among alternative measurement techniques, but the laser link margin is very small, permitting only very few stations to obtain valid measurements. Therefore the next generation of the LLR (Lunar Laser Ranging) technique should aim for a substantial improvement. We propose a one-way ranging concept involving Laser transponders. A particular strength of this proposed experiment is given when several stations are ranging to the Moon simultaneously and/or when several geodetic stations on the Moon are used simultaneously, as this is expected to improve the modeling geometry and data quality. The proposed experiment may well initiate the installation of new observing stations on Earth – perhaps within the infrastructure of existing astronomical observatories. At the same time it allows many more SLR (Satellite Laser Ranging) stations from the existing network to obtain measurements from the Moon. In the case of the beacon mode, only passive optical receivers are needed on the ground. In addition, we propose to deploy and operate a microwave receiver/transmitter with precisely known mechanical local ties to the laser beacon/receiver, which will permit observations of the tangential position of the Moon with respect to the celestial frame. We also propose to include a GNSS microwave transmitter into the equipment realizing a “GPS/Galileo satellite on the Moon” that is tracked together with GNSS satellites by receivers on the ground and possibly on a future generation of GNSS satellites. The ultimate objectives of our proposal are threefold, the improvement of the reference frames for the Earth, a better understanding of the Moon's interior, and a better determination of the parameters of General Relativity.