The Experts below are selected from a list of 40143 Experts worldwide ranked by ideXlab platform
John J Degnan - One of the best experts on this subject based on the ideXlab platform.
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The next generation of satellite Laser Ranging systems
Journal of Geodesy, 2018Co-Authors: Matthew Wilkinson, John J Degnan, Georg Kirchner, Ivan Prochazka, Peter J. Dunn, Zhang Zhongping, Ulrich Schreiber, Christopher Moore, Victor Shargorodskiy, Mikhail SadovnikovAbstract:Satellite Laser Ranging (SLR) stations in the International Laser Ranging Service (ILRS) global tracking network come in different shapes and sizes and were built by different institutions at different times using different technologies. In addition, those stations that have upgraded their systems and equipment are often operating a complementary mix of old and new. Such variety reduces the risk of systematic errors across all ILRS stations, and an operational advantage at one station can inform the direction and choices at another station. This paper describes the evolution of the ILRS network and the emergence of a new generation of SLR station, operating at kHz repetition rates, firing ultra-short Laser pulses that are timestamped by epoch timers accurate to a few picoseconds. It discusses current trends, such as increased automation, higher repetition rate SLR and the challenges of eliminating systematic biases, and highlights possibilities in new technology. In addition to meeting the growing demand for Laser tracking support from an increasing number of SLR targets, including a variety of Global Navigation Satellite Systems satellites, ILRS stations are striving to: meet the millimetre range accuracy science goals of the Global Geodetic Observing System; make Laser range measurements to space debris objects in the absence of high optical cross-sectional retro-reflectors; further advances in deep space Laser Ranging and Laser communications; and demonstrate accurate Laser time transfer between continents.
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Advancing tests of relativistic gravity via Laser Ranging to Phobos
Experimental Astronomy, 2010Co-Authors: Slava G. Turyshev, William Farr, André R. Girerd, Thomas W. Murphy, Hamid Hemmati, William M. Folkner, James G. Williams, John J DegnanAbstract:Phobos Laser Ranging (PLR) is a concept for a space mission designed to advance tests of relativistic gravity in the solar system. PLR’s primary objective is to measure the curvature of space around the Sun, represented by the Eddington parameter γ , with an accuracy of two parts in 10^7, thereby improving today’s best result by two orders of magnitude. Other mission goals include measurements of the time-rate-of-change of the gravitational constant, G and of the gravitational inverse square law at 1.5-AU distances—with up to two orders-of-magnitude improvement for each. The science parameters will be estimated using Laser Ranging measurements of the distance between an Earth station and an active Laser transponder on Phobos capable of reaching mm-level range resolution. A transponder on Phobos sending 0.25-mJ, 10-ps pulses at 1 kHz, and receiving asynchronous 1-kHz pulses from earth via a 12-cm aperture will permit links that even at maximum range will exceed a photon per second. A total measurement precision of 50 ps demands a few hundred photons to average to 1-mm (3.3 ps) range precision. Existing satellite Laser Ranging (SLR) facilities—with appropriate augmentation—may be able to participate in PLR. Since Phobos’ orbital period is about 8 h, each observatory is guaranteed visibility of the Phobos instrument every Earth day. Given the current technology readiness level, PLR could be started in 2011 for launch in 2016 for 3 yr of science operations. We discuss the PLR’s science objectives, instrument, and mission design. We also present the details of science simulations performed to support the mission’s primary objectives.
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advancing tests of relativistic gravity via Laser Ranging to phobos
arXiv: General Relativity and Quantum Cosmology, 2010Co-Authors: Slava G. Turyshev, André R. Girerd, Thomas W. Murphy, John J Degnan, Hamid Hemmati, William M. Folkner, James G. Williams, William H. FarrAbstract:Phobos Laser Ranging (PLR) is a concept for a space mission designed to advance tests of relativistic gravity in the solar system. PLR's primary objective is to measure the curvature of space around the Sun, represented by the Eddington parameter $\gamma$, with an accuracy of two parts in $10^7$, thereby improving today's best result by two orders of magnitude. Other mission goals include measurements of the time-rate-of-change of the gravitational constant, $G$ and of the gravitational inverse square law at 1.5 AU distances--with up to two orders-of-magnitude improvement for each. The science parameters will be estimated using Laser Ranging measurements of the distance between an Earth station and an active Laser transponder on Phobos capable of reaching mm-level range resolution. A transponder on Phobos sending 0.25 mJ, 10 ps pulses at 1 kHz, and receiving asynchronous 1 kHz pulses from earth via a 12 cm aperture will permit links that even at maximum range will exceed a photon per second. A total measurement precision of 50 ps demands a few hundred photons to average to 1 mm (3.3 ps) range precision. Existing satellite Laser Ranging (SLR) facilities--with appropriate augmentation--may be able to participate in PLR. Since Phobos' orbital period is about 8 hours, each observatory is guaranteed visibility of the Phobos instrument every Earth day. Given the current technology readiness level, PLR could be started in 2011 for launch in 2016 for 3 years of science operations. We discuss the PLR's science objectives, instrument, and mission design. We also present the details of science simulations performed to support the mission's primary objectives.
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Satellite Laser Ranging, status and impact for WEGENER
Journal of Geodynamics, 1998Co-Authors: Erik Vermaat, John J Degnan, Peter J. Dunn, Ron Noomen, Andrew T. SinclairAbstract:Abstract The principles of the technique of Satellite Laser Ranging are briefly explained and the current status and outlook for further development are described. Results for the application of this technique in the WEGENER program are reviewed and strategies for continued contributions to this program from stationary and transportable Laser Ranging systems are presented.
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Eighth International Workshop on Laser Ranging Instrumentation
1993Co-Authors: John J DegnanAbstract:The Eighth International Workshop for Laser Ranging Instrumentation was held in Annapolis, Maryland in May 1992, and was sponsored by the NASA Goddard Space Flight Center in Greenbelt, Maryland. The workshop is held once every 2 to 3 years under differing institutional sponsorship and provides a forum for participants to exchange information on the latest developments in satellite and lunar Laser Ranging hardware, software, science applications, and data analysis techniques. The satellite Laser Ranging (SLR) technique provides sub-centimeter precision range measurements to artificial satellites and the Moon. The data has application to a wide range of Earth and lunar science issues including precise orbit determination, terrestrial reference frames, geodesy, geodynamics, oceanography, time transfer, lunar dynamics, gravity and relativity.
Slava G. Turyshev - One of the best experts on this subject based on the ideXlab platform.
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Extending Science from Lunar Laser Ranging
2020Co-Authors: Vishnu Viswanathan, Slava G. Turyshev, James G. Williams, Douglas G. Currie, Stephen M. Merkowitz, Erwan Mazarico, Anton I. Ermakov, Nicolas Rambaux, Agnès Fienga, C. CourdeAbstract:The Lunar Laser Ranging (LLR) experiment has accumulated 50 years of range data of improving accuracy from ground stations to the Laser retroreflector arrays (LRAs) on the lunar surface. The upcoming decade offers several opportunities to break new ground in data precision through the deployment of the next generation of single corner-cube lunar retroreflectors and active Laser transponders. This is likely to expand the LLR station network. Lunar dynamical models and analysis tools have the potential to improve and fully exploit the long temporal baseline and precision allowed by millimetric LLR data. Some of the model limitations are outlined for future efforts. Differential observation techniques will help mitigate some of the primary limiting factors and reach unprecedented accuracy. Such observations and techniques may enable the detection of several subtle signatures required to understand the dynamics of the Earth-Moon system and the deep lunar interior. LLR model improvements would impact multi-disciplinary fields that include lunar and planetary science, Earth science, fundamental physics, celestial mechanics and ephemerides.
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Corner-cube retro-reflector instrument for advanced lunar Laser Ranging
Experimental Astronomy, 2013Co-Authors: Slava G. Turyshev, William M. Folkner, James G. Williams, Gary M. Gutt, Richard T. Baran, Randall C. Hein, Ruwan P. Somawardhana, John A. Lipa, Suwen WangAbstract:Lunar Laser Ranging (LLR) has made major contributions to our understanding of the Moon’s internal structure and the dynamics of the Earth–Moon system. Because of the recent improvements of the ground-based Laser Ranging facilities, the present LLR measurement accuracy is limited by the retro-reflectors currently on the lunar surface, which are arrays of small corner-cubes. Because of lunar librations, the surfaces of these arrays do not, in general, point directly at the Earth. This effect results in a spread of arrival times, because each cube that comprises the retroreflector is at a slightly different distance from the Earth, leading to the reduced Ranging accuracy. Thus, a single, wide aperture corner-cube could have a clear advantage. In addition, after nearly four decades of successful operations the retro-reflectors arrays currently on the Moon started to show performance degradation; as a result, they yield still useful, but much weaker return signals. Thus, fresh and bright instruments on the lunar surface are needed to continue precision LLR measurements. We have developed a new retro-reflector design to enable advanced LLR operations. It is based on a single, hollow corner cube with a large aperture for which preliminary thermal, mechanical, and optical design and analysis have been performed. The new instrument will be able to reach an Earth–Moon range precision of 1-mm in a single pulse while being subjected to significant thermal variations present on the lunar surface, and will have low mass to allow robotic deployment. Here we report on our design results and instrument development effort.
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Advancing tests of relativistic gravity via Laser Ranging to Phobos
Experimental Astronomy, 2010Co-Authors: Slava G. Turyshev, William Farr, André R. Girerd, Thomas W. Murphy, Hamid Hemmati, William M. Folkner, James G. Williams, John J DegnanAbstract:Phobos Laser Ranging (PLR) is a concept for a space mission designed to advance tests of relativistic gravity in the solar system. PLR’s primary objective is to measure the curvature of space around the Sun, represented by the Eddington parameter γ , with an accuracy of two parts in 10^7, thereby improving today’s best result by two orders of magnitude. Other mission goals include measurements of the time-rate-of-change of the gravitational constant, G and of the gravitational inverse square law at 1.5-AU distances—with up to two orders-of-magnitude improvement for each. The science parameters will be estimated using Laser Ranging measurements of the distance between an Earth station and an active Laser transponder on Phobos capable of reaching mm-level range resolution. A transponder on Phobos sending 0.25-mJ, 10-ps pulses at 1 kHz, and receiving asynchronous 1-kHz pulses from earth via a 12-cm aperture will permit links that even at maximum range will exceed a photon per second. A total measurement precision of 50 ps demands a few hundred photons to average to 1-mm (3.3 ps) range precision. Existing satellite Laser Ranging (SLR) facilities—with appropriate augmentation—may be able to participate in PLR. Since Phobos’ orbital period is about 8 h, each observatory is guaranteed visibility of the Phobos instrument every Earth day. Given the current technology readiness level, PLR could be started in 2011 for launch in 2016 for 3 yr of science operations. We discuss the PLR’s science objectives, instrument, and mission design. We also present the details of science simulations performed to support the mission’s primary objectives.
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advancing tests of relativistic gravity via Laser Ranging to phobos
arXiv: General Relativity and Quantum Cosmology, 2010Co-Authors: Slava G. Turyshev, André R. Girerd, Thomas W. Murphy, John J Degnan, Hamid Hemmati, William M. Folkner, James G. Williams, William H. FarrAbstract:Phobos Laser Ranging (PLR) is a concept for a space mission designed to advance tests of relativistic gravity in the solar system. PLR's primary objective is to measure the curvature of space around the Sun, represented by the Eddington parameter $\gamma$, with an accuracy of two parts in $10^7$, thereby improving today's best result by two orders of magnitude. Other mission goals include measurements of the time-rate-of-change of the gravitational constant, $G$ and of the gravitational inverse square law at 1.5 AU distances--with up to two orders-of-magnitude improvement for each. The science parameters will be estimated using Laser Ranging measurements of the distance between an Earth station and an active Laser transponder on Phobos capable of reaching mm-level range resolution. A transponder on Phobos sending 0.25 mJ, 10 ps pulses at 1 kHz, and receiving asynchronous 1 kHz pulses from earth via a 12 cm aperture will permit links that even at maximum range will exceed a photon per second. A total measurement precision of 50 ps demands a few hundred photons to average to 1 mm (3.3 ps) range precision. Existing satellite Laser Ranging (SLR) facilities--with appropriate augmentation--may be able to participate in PLR. Since Phobos' orbital period is about 8 hours, each observatory is guaranteed visibility of the Phobos instrument every Earth day. Given the current technology readiness level, PLR could be started in 2011 for launch in 2016 for 3 years of science operations. We discuss the PLR's science objectives, instrument, and mission design. We also present the details of science simulations performed to support the mission's primary objectives.
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Combined Laser communications and Laser Ranging transponder for Moon and Mars
Free-Space Laser Communication Technologies XXI, 2009Co-Authors: Hamid Hemmati, Slava G. Turyshev, Kevin M. Birnbaum, William H. Farr, Abhijit BiswasAbstract:High-resolution active Laser Ranging systems for Moon, Mars and beyond are analyzed. Both stand-alone Laser-Ranging transponders, and Laser-communications systems configured to provide millimeter-level Ranging data are analyzed. It is shown that a combined dual-function Laser-communications and Laser-Ranging system is feasible.
James G. Williams - One of the best experts on this subject based on the ideXlab platform.
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Extending Science from Lunar Laser Ranging
2020Co-Authors: Vishnu Viswanathan, Slava G. Turyshev, James G. Williams, Douglas G. Currie, Stephen M. Merkowitz, Erwan Mazarico, Anton I. Ermakov, Nicolas Rambaux, Agnès Fienga, C. CourdeAbstract:The Lunar Laser Ranging (LLR) experiment has accumulated 50 years of range data of improving accuracy from ground stations to the Laser retroreflector arrays (LRAs) on the lunar surface. The upcoming decade offers several opportunities to break new ground in data precision through the deployment of the next generation of single corner-cube lunar retroreflectors and active Laser transponders. This is likely to expand the LLR station network. Lunar dynamical models and analysis tools have the potential to improve and fully exploit the long temporal baseline and precision allowed by millimetric LLR data. Some of the model limitations are outlined for future efforts. Differential observation techniques will help mitigate some of the primary limiting factors and reach unprecedented accuracy. Such observations and techniques may enable the detection of several subtle signatures required to understand the dynamics of the Earth-Moon system and the deep lunar interior. LLR model improvements would impact multi-disciplinary fields that include lunar and planetary science, Earth science, fundamental physics, celestial mechanics and ephemerides.
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Corner-cube retro-reflector instrument for advanced lunar Laser Ranging
Experimental Astronomy, 2013Co-Authors: Slava G. Turyshev, William M. Folkner, James G. Williams, Gary M. Gutt, Richard T. Baran, Randall C. Hein, Ruwan P. Somawardhana, John A. Lipa, Suwen WangAbstract:Lunar Laser Ranging (LLR) has made major contributions to our understanding of the Moon’s internal structure and the dynamics of the Earth–Moon system. Because of the recent improvements of the ground-based Laser Ranging facilities, the present LLR measurement accuracy is limited by the retro-reflectors currently on the lunar surface, which are arrays of small corner-cubes. Because of lunar librations, the surfaces of these arrays do not, in general, point directly at the Earth. This effect results in a spread of arrival times, because each cube that comprises the retroreflector is at a slightly different distance from the Earth, leading to the reduced Ranging accuracy. Thus, a single, wide aperture corner-cube could have a clear advantage. In addition, after nearly four decades of successful operations the retro-reflectors arrays currently on the Moon started to show performance degradation; as a result, they yield still useful, but much weaker return signals. Thus, fresh and bright instruments on the lunar surface are needed to continue precision LLR measurements. We have developed a new retro-reflector design to enable advanced LLR operations. It is based on a single, hollow corner cube with a large aperture for which preliminary thermal, mechanical, and optical design and analysis have been performed. The new instrument will be able to reach an Earth–Moon range precision of 1-mm in a single pulse while being subjected to significant thermal variations present on the lunar surface, and will have low mass to allow robotic deployment. Here we report on our design results and instrument development effort.
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Advancing tests of relativistic gravity via Laser Ranging to Phobos
Experimental Astronomy, 2010Co-Authors: Slava G. Turyshev, William Farr, André R. Girerd, Thomas W. Murphy, Hamid Hemmati, William M. Folkner, James G. Williams, John J DegnanAbstract:Phobos Laser Ranging (PLR) is a concept for a space mission designed to advance tests of relativistic gravity in the solar system. PLR’s primary objective is to measure the curvature of space around the Sun, represented by the Eddington parameter γ , with an accuracy of two parts in 10^7, thereby improving today’s best result by two orders of magnitude. Other mission goals include measurements of the time-rate-of-change of the gravitational constant, G and of the gravitational inverse square law at 1.5-AU distances—with up to two orders-of-magnitude improvement for each. The science parameters will be estimated using Laser Ranging measurements of the distance between an Earth station and an active Laser transponder on Phobos capable of reaching mm-level range resolution. A transponder on Phobos sending 0.25-mJ, 10-ps pulses at 1 kHz, and receiving asynchronous 1-kHz pulses from earth via a 12-cm aperture will permit links that even at maximum range will exceed a photon per second. A total measurement precision of 50 ps demands a few hundred photons to average to 1-mm (3.3 ps) range precision. Existing satellite Laser Ranging (SLR) facilities—with appropriate augmentation—may be able to participate in PLR. Since Phobos’ orbital period is about 8 h, each observatory is guaranteed visibility of the Phobos instrument every Earth day. Given the current technology readiness level, PLR could be started in 2011 for launch in 2016 for 3 yr of science operations. We discuss the PLR’s science objectives, instrument, and mission design. We also present the details of science simulations performed to support the mission’s primary objectives.
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advancing tests of relativistic gravity via Laser Ranging to phobos
arXiv: General Relativity and Quantum Cosmology, 2010Co-Authors: Slava G. Turyshev, André R. Girerd, Thomas W. Murphy, John J Degnan, Hamid Hemmati, William M. Folkner, James G. Williams, William H. FarrAbstract:Phobos Laser Ranging (PLR) is a concept for a space mission designed to advance tests of relativistic gravity in the solar system. PLR's primary objective is to measure the curvature of space around the Sun, represented by the Eddington parameter $\gamma$, with an accuracy of two parts in $10^7$, thereby improving today's best result by two orders of magnitude. Other mission goals include measurements of the time-rate-of-change of the gravitational constant, $G$ and of the gravitational inverse square law at 1.5 AU distances--with up to two orders-of-magnitude improvement for each. The science parameters will be estimated using Laser Ranging measurements of the distance between an Earth station and an active Laser transponder on Phobos capable of reaching mm-level range resolution. A transponder on Phobos sending 0.25 mJ, 10 ps pulses at 1 kHz, and receiving asynchronous 1 kHz pulses from earth via a 12 cm aperture will permit links that even at maximum range will exceed a photon per second. A total measurement precision of 50 ps demands a few hundred photons to average to 1 mm (3.3 ps) range precision. Existing satellite Laser Ranging (SLR) facilities--with appropriate augmentation--may be able to participate in PLR. Since Phobos' orbital period is about 8 hours, each observatory is guaranteed visibility of the Phobos instrument every Earth day. Given the current technology readiness level, PLR could be started in 2011 for launch in 2016 for 3 years of science operations. We discuss the PLR's science objectives, instrument, and mission design. We also present the details of science simulations performed to support the mission's primary objectives.
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SPACE-BASED TESTS OF GRAVITY WITH Laser Ranging
International Journal of Modern Physics D, 2007Co-Authors: Slava G. Turyshev, James G. WilliamsAbstract:Existing capabilities of Laser Ranging, optical interferometry, and metrology, in combination with precision frequency standards, atom-based quantum sensors, and drag-free technologies, are critical for space-based tests of fundamental physics; as a result of the recent progress in these disciplines, the entire area is poised for major advances. Thus, accurate Ranging to the Moon and Mars will provide significant improvements in several gravity tests, namely the equivalence principle, geodetic precession, PPN parameters β and γ, and possible variation of the gravitational constant G. Other tests will become possible with the development of an optical architecture that allows one to proceed from meter to centimeter to millimeter range accuracies on interplanetary distances. Motivated by anticipated accuracy gains, we discuss the recent renaissance in lunar Laser Ranging and consider future relativistic gravity experiments with precision Laser Ranging over interplanetary distances.
Yao-heng Xiong - One of the best experts on this subject based on the ideXlab platform.
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satellite Laser Ranging using superconducting nanowire single photon detectors at 1064 nm wavelength
Optics Letters, 2016Co-Authors: Li Xue, Labao Zhang, Dongsheng Zhai, Sen Zhang, Lin Kang, Jian Chen, Yao-heng XiongAbstract:Satellite Laser Ranging operating at 1064 nm wavelength using superconducting nanowire single-photon detectors (SNSPDs) is successfully demonstrated. A SNSPD with an intrinsic quantum efficiency of 80% and a dark count rate of 100 cps at 1064 nm wavelength is developed and introduced to Yunnan Observatory in China. With improved closed-loop telescope systems (field of view of about 26′′), satellites including Cryosat, Ajisai, and Glonass with ranges of 1600 km, 3100 km, and 19,500 km, respectively, are experimentally ranged with mean echo rates of 1200/min, 4200/min, and 320/min, respectively. To the best of our knowledge, this is the first demonstration of Laser Ranging for satellites using SNSPDs at 1064 nm wavelength. Theoretical analysis of the detection efficiency and the mean echo rate for typical satellites indicate that it is possible for a SNSPD to range satellites from low Earth orbit to geostationary Earth orbit.
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Research on Diffuse Satellite Laser Ranging
2008Co-Authors: Jun Liu, Yao-heng XiongAbstract:The satellite Laser Ranging serves as a multitudinous discipline technical method achievement to study the Earth dynamics,the atmospheric dynamics,the geophysics and so on.This paper is based on the satellite Laser Ranging,and probe the satellite that does not have the retrodirective reflector.It is from the theory and experimentation mostly,and predict that how much the Laser projection energy power can detect how for the distance ranges of the satellite,which also relate to the Laser light beam parameter.The paper is based on the tradition Laser Ranging obtaining,and put forward the method from the theory to the experimental technique,which the actual diffuse reflection predict the Laser Ranging.
Stephen M. Merkowitz - One of the best experts on this subject based on the ideXlab platform.
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Extending Science from Lunar Laser Ranging
2020Co-Authors: Vishnu Viswanathan, Slava G. Turyshev, James G. Williams, Douglas G. Currie, Stephen M. Merkowitz, Erwan Mazarico, Anton I. Ermakov, Nicolas Rambaux, Agnès Fienga, C. CourdeAbstract:The Lunar Laser Ranging (LLR) experiment has accumulated 50 years of range data of improving accuracy from ground stations to the Laser retroreflector arrays (LRAs) on the lunar surface. The upcoming decade offers several opportunities to break new ground in data precision through the deployment of the next generation of single corner-cube lunar retroreflectors and active Laser transponders. This is likely to expand the LLR station network. Lunar dynamical models and analysis tools have the potential to improve and fully exploit the long temporal baseline and precision allowed by millimetric LLR data. Some of the model limitations are outlined for future efforts. Differential observation techniques will help mitigate some of the primary limiting factors and reach unprecedented accuracy. Such observations and techniques may enable the detection of several subtle signatures required to understand the dynamics of the Earth-Moon system and the deep lunar interior. LLR model improvements would impact multi-disciplinary fields that include lunar and planetary science, Earth science, fundamental physics, celestial mechanics and ephemerides.
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Tests of Gravity Using Lunar Laser Ranging
Living Reviews in Relativity, 2010Co-Authors: Stephen M. MerkowitzAbstract:Lunar Laser Ranging (LLR) has been a workhorse for testing general relativity over the past four decades. The three retroreflector arrays put on the Moon by the Apollo astronauts and the French built arrays on the Soviet Lunokhod rovers continue to be useful targets, and have provided the most stringent tests of the Strong Equivalence Principle and the time variation of Newton’s gravitational constant. The relatively new Ranging system at the Apache Point 3.5 meter telescope now routinely makes millimeter level range measurements. Incredibly, it has taken 40 years for ground station technology to advance to the point where characteristics of the lunar retroreflectors are limiting the precision of the range measurements. In this article, we review the gravitational science and technology of lunar Laser Ranging and discuss prospects for the future.
