2 December 2019
In the context of future space missions in fundamental physics (SAGAS, STE-QUEST, OSS, ….) a coherent laser link for clock comparisons, navigation, and data transmission will be essential. This is the long term aim of DOLL (Deep Space Optical Laser Link).
- The 1.5 m lunar/satellite ranging telescope at the Observatoire de la côte d’Azur (Calern site) used for Mini-DOLL.
In a terrestrial environment a satellite to ground coherent optical link (Mini-DOLL project) has applications for clock comparison, satellite orbit determination (optical Doppler ranging) and high bandwidth data transmission by phase modulation.
In this type of link the atmosphere is the main limiting factor because of atmospheric turbulence that adds phase and amplitude noise (scintillation) both of which diminish the link performance. The main objectives of the Mini-DOLL project are:
- Demonstrate the feasibility of a coherent optical link through the turbulent atmosphere.
- Study and quantify the phase and amplitude noise introduced by atmospheric turbulence on the up and down link.
- Study transverse phase coherence and the required degree of adaptive optics.
The project is carried out in collaboration with Observatoire de la Côte d’Azur and ONERA. The tests take place at the Calern observation site using the 1.5 m lunar and satellite ranging telescope Méo.
At present we are studying turbulence induced amplitude and phase noise by numerical simulation (collaboration with ONERA) for realistic satellite-ground links, and the possibility of reducing that noise by two-way compensation techniques [Robert et al., Phys. rev. A, 93, 033860, 2016].
More recently we have started a collaboration with CNES and the university of Western Australia to build a link between two ground stations via a low altitude platform (drone, plane, balloon, stratospheric carrier) for applications in chronometric geodesy.