In this project we are concerned with the Moon's deformation in response to tidal forces raised by the Earth and Sun. A purely elastic body would deform instantaneously under varying tidal forcing. However, the Moon is to a certain degree viscous, in which case the deformation occurs somewhat behind phase and the body dissipates energy through internal friction. Tidal response thus provides a constraint on the internal structure and rheology, which are in turn useful for studying the origin and evolution of the Earth-Moon system. A particular focus is the impact of lunar deformation on the motion of orbiting spacecraft, such as the Lunar Reconnaissance Orbiter (LRO). We use both numerical and analytical methods to analyze how spacecraft orbits evolve around the viscoelastic Moon and search for relevant and potentially detectable signals in time and spectral domains. We assess the impact of the dynamic effects in precise orbit computations and error budget of the published spacecraft orbits. If applicable, we aim for a consistent, viable strategy to improve the present orbit solutions.

This research is within the project “Lunar tidal Deformation from earth-based and orbital Laser Ranging”, which aims to synthesize observations and models based on Earth-based Lunar Laser Ranging and orbit-based Laser Altimetry in order to improve the determination of the tidal deformation of the Moon and consequently the present dissipation in the Earth-Moon system (funded jointly by the CNRS and DFG). Close collaboration exists with other institutes, e.g., Deutsches Zentrum für Luft- und Raumfahrt (Berlin-Adlershof), Observatoire de la Côte d'Azur (France), Technical University of Delft (The Netherlands), Observatoire de Paris (France), Università di Bologna (Italy), Sezione di Sismologia e Tettonofisica (Italy).