LLR data analysis and impact on lunar dynamics from recent developments at OCA LLR Station

International audienceSince late 2014, OCA LLR station has been able to range with infrared wavelength (1064nm). IR ranging provides both temporal and spatial improvement in the LLR observations. IR detection also permits in densification of normal points, including the L1 and L2 retroreflectors due to better signal to noise ratio. This contributes to a better modelisation of the lunar libration. The hypothesis of lunar dust and environmental effects due to the chromatic behavior noticed on returns from L2 retroreflector is discussed. In addition, data analysis shows that the effect of retroreflector tilt and the use of calibration profile for the normal point deduction algorithm, contributes to improving the precision of normal points, thereby impacting lunar dynamical models and inner physics

LLR data analysis and impact on lunar dynamics from recent developments at OCA LLR Station

International audienceSince late 2014, OCA LLR station has been able to range with infrared wavelength (1064nm). IR ranging provides both temporal and spatial improvement in the LLR observations. IR detection also permits in densification of normal points, including the L1 and L2 retroreflectors due to better signal to noise ratio. This contributes to a better modelisation of the lunar libration. The hypothesis of lunar dust and environmental effects due to the chromatic behavior noticed on returns from L2 retroreflector is discussed. In addition, data analysis shows that the effect of retroreflector tilt and the use of calibration profile for the normal point deduction algorithm, contributes to improving the precision of normal points, thereby impacting lunar dynamical models and inner physics

Recent Progress in Lunar Laser Ranging at Grasse Laser Ranging Station

International audienceBased on a fully passive space segment, the Lunar Laser Ranging experiment is the last of the Apollo Lunar Surface Experiments Package to operate. Observations from Grasse Lunar Laser Ranging station have been realized on a daily basis since the first echoes obtained in 1981. We will give a brief summary of the progress made at Grasse Laser Ranging facility (Observatoire de la Côte d'Azur, Calern Plateau on the french riviera) since the first echoes. The current performances, driven by the use of infrared wavelength, are presented for the year 2018. The capacities of Grasse Lunar Laser Ranging station have been clearly improved in terms of budget link, reflectors numbers and synodic period observation

Recent Progress in Lunar Laser Ranging at Grasse Laser Ranging Station

International audienceBased on a fully passive space segment, the Lunar Laser Ranging experiment is the last of the Apollo Lunar Surface Experiments Package to operate. Observations from Grasse Lunar Laser Ranging station have been realized on a daily basis since the first echoes obtained in 1981. We will give a brief summary of the progress made at Grasse Laser Ranging facility (Observatoire de la Côte d'Azur, Calern Plateau on the french riviera) since the first echoes. The current performances, driven by the use of infrared wavelength, are presented for the year 2018. The capacities of Grasse Lunar Laser Ranging station have been clearly improved in terms of budget link, reflectors numbers and synodic period observation

Recent Progress in Lunar Laser Ranging at Grasse Laser Ranging Station

International audienceBased on a fully passive space segment, the lunar laser ranging experiment is the last of the Apollo Lunar Surface Experiments Package to operate. Observations from the Grasse lunar laser ranging station have been made on a daily basis since the first echoes obtained in 1981. In this paper, first, we review the principle and the technical aspects of lunar laser ranging. We then give a brief summary of the progress made at the Grasse laser ranging facility (Observatoire de la Côte d'Azur, Calern Plateau on the French Riviera) since the first echoes. The current performance, driven by the use of an infrared wavelength laser, is presented in the last section for the year 2018

Downlink communication experiments with OSIRISv1 laser terminal onboard Flying Laptop satellite

Downlink measurement campaigns from the optical downlink terminal OSIRISv1 onboard the LEO satellite Flying Laptop were carried out with the French Observatoire de la Cote d Azur and with two Optical Ground Stations of the German Aerospace Center. On/off keyed data at 39 Mb/s were modulated on the laser signal, and according telecom reception was performed by the ground stations. The pointing of the laser terminal was achieved by open-loop body pointing of the satellite orientation, with its star sensor as attitude control signal. We report here on the measurements and investigations of the downlink signal and the data transmission

Paris Observatory Lunar Analysis Center: from LLR predictions to tests of fundamental Physics

International audiencePOLAC (Paris Observatory Lunar Analysis Center) is an ILRS analysis center founded by J. Chapront, M. Chapront-Touzé and G. Francou in 1996. They developed in the 80's a semi-analytical solution of the lunar motion named ELP (Ephémérides lunaires Parisienne). Thus, the original purpose of POLAC was the adjustment of ELP to the lunar laser ranging observations (LLR) for improving the determination of fundamental astronomical parameters, such as the free modes of lunar physical librations, the tidal secular acceleration of the lunar longitude, or the transformation between celestial reference systems. Since the beginning, POLAC worked in close collaboration with the laser ranging station of Grasse (MéO) by providing a posteriori validation of their LLR normal points in order to avoid calibration and format issues. <P />Since 2010 POLAC has evolved. Firstly, it additionally provides predictions for laser ranging observations - mainly for the Moon tracking but also, in an experimental mode, for two ways LRO (Lunar Reconnaissance Orbiter) tracking . The POLAC LLR predictions, originally dedicated and optimized for MéO station, are now the official ILRS prediction for LLR. Secondly, with the elaboration of a new lunar ephemeris called ELPN (Ephéméride lunaire Parisienne Numérique), POLAC also takes part to the long legacy of testing fundamental Physics with laser ranges to the Moon. Indeed, even if ELPN was built originally in the General Relativity (GR) framework, it allows for GR alternative theories of gravity as well. One of particular interest is the Standard Model Extension (SME) which parametrizes Lorentz symmetry violations, notably in the pure gravity sector and in the matter sector of the formalism. By fitting ELPN in the SME framework to the 50 years of collected data, we have been able to provide stringent and realistic estimates on possible Lorentz symmetry violations arising at the level of the weak and the strong Einstein equivalence principles

Paris Observatory Lunar Analysis Center: from LLR predictions to tests of fundamental Physics

International audiencePOLAC (Paris Observatory Lunar Analysis Center) is an ILRS analysis center founded by J. Chapront, M. Chapront-Touzé and G. Francou in 1996. They developed in the 80's a semi-analytical solution of the lunar motion named ELP (Ephémérides lunaires Parisienne). Thus, the original purpose of POLAC was the adjustment of ELP to the lunar laser ranging observations (LLR) for improving the determination of fundamental astronomical parameters, such as the free modes of lunar physical librations, the tidal secular acceleration of the lunar longitude, or the transformation between celestial reference systems. Since the beginning, POLAC worked in close collaboration with the laser ranging station of Grasse (MéO) by providing a posteriori validation of their LLR normal points in order to avoid calibration and format issues. <P />Since 2010 POLAC has evolved. Firstly, it additionally provides predictions for laser ranging observations - mainly for the Moon tracking but also, in an experimental mode, for two ways LRO (Lunar Reconnaissance Orbiter) tracking . The POLAC LLR predictions, originally dedicated and optimized for MéO station, are now the official ILRS prediction for LLR. Secondly, with the elaboration of a new lunar ephemeris called ELPN (Ephéméride lunaire Parisienne Numérique), POLAC also takes part to the long legacy of testing fundamental Physics with laser ranges to the Moon. Indeed, even if ELPN was built originally in the General Relativity (GR) framework, it allows for GR alternative theories of gravity as well. One of particular interest is the Standard Model Extension (SME) which parametrizes Lorentz symmetry violations, notably in the pure gravity sector and in the matter sector of the formalism. By fitting ELPN in the SME framework to the 50 years of collected data, we have been able to provide stringent and realistic estimates on possible Lorentz symmetry violations arising at the level of the weak and the strong Einstein equivalence principles

Optical bench development for laser communication OSIRIS mission at Grasse (France) station

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Time Transfer by Laser Link - T2L2: Current status and future experiments

International audienceT2L2 (Time Transfer by Laser Link), developed by both CNES and OCA permits the synchronization of remote ultra stable clocks over intercontinental distances. The principle is derived from laser telemetry technology with dedicated space equipment deigned to record arrival time of laser pulses at the satellite. Using laser pulses instead of radio frequency signals, T2L2 permits to realize some links between distant clocks with a time stability of a few picoseconds and accuracy better than 100 ps. The T2L2 space instrument is in operation onboard the satellite Jason 2 since June 2008. Several campaigns were done to demonstrate both the ultimate time accuracy and time stability capabilities. It includes some experiments implemented in co-location to directly compare T2L2 time transfer residuals with the direct link between stations, and some ground to ground time transfer between ultra stable clocks. Important works have been done, between OCA and OP, to accurately compare T2L2 with microwave time transfer GPS and TWSTFT. These comparisons are based on laser station calibrations with a dedicated T2L2 calibration station designed to accurately set the optical reference of the laser station within the PPS reference of the microwave systems. Other experiments are also planned in the future: 3D localization with the lunar space vehicle LRO, T2L2 coverage extension over the Pacific Ocean (Tahiti), DORIS comparison and a third international campaign