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A Critical Review of the Lunar Laser Ranging

Received: 14 July 2020     Accepted: 31 July 2020     Published: 20 August 2020
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Abstract

This paper provides an overview of the Lunar Laser Ranging (LLR) experiments. The measurement principle is explained and its theory is derived. Both contributions, the direct reflected light from retroreflectors as well as the scattered light from the lunar surface are considered. The measurement results from the Sixties until 2007 are then compared between different LLR stations and with the theoretical forecast. The very first experiment was in 1962: a laser beam was directed to the Moon and the scattered light from the lunar surface was detected. The number of received photons was in line with the theory. Then from 1969 the laser beams were directed to retroreflectors placed by Apollo astronauts and Luna space crafts. Retroreflectors are on the one hand reference points for long term measurements; on the other hand they deliver a much stronger return signal compared to the scattered return. But none of the stations could measure the expected amplification of the retroreflectors. The number of received photons remained in line with measurements to the bare surface of the Moon. Therefore either all retroreflectors have degraded such that their return signals fit to the scattered return from the lunar soil or the measurements were indeed taken to the lunar surface only.

Published in American Journal of Astronomy and Astrophysics (Volume 8, Issue 3)
DOI 10.11648/j.ajaa.20200803.11
Page(s) 39-44
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2020. Published by Science Publishing Group

Keywords

LLR, Retroreflector, Scattering

References
[1] Ivan Prochazka et al., “Photon counting detector for space debris laser tracking and lunar laser ranging,” Advances in Space Research 54 (4): 755–758 August 2014.
[2] N. Thomas et al., “The BepiColombo Laser Altimeter (BELA): concept and baseline design,” Planetary and Space Science 55 (2007) 1398–1413.
[3] John J. Degnan, “Millimeter accuracy satellite laser ranging: a review,” Geodynamics Series Volume 25, 1993.
[4] Bernard J. Klein and John J. Degnan, “Optical Antenna Gain. 1: Transmitting Antennas,” APPLIED OPTICS / Vol. 13, No. 9 / September 1974.
[5] J. Vernin & C. Muñoz-Tunón, “The Intrinsic Seeing Quality at the WHT Site” (William Herschel Telescope, La Palma, 2‘344m), 1994 http://www.ing.iac.es/Astronomy/development/hap/dimm.html.
[6] Apollo 11 Preliminary Science Report (1969), http://history.nasa.gov/alsj/a11/a11psr.html.
[7] J. O. Dickey et al., “Lunar Laser Ranging: a continuing legacy of the Apollo program,” Invited Review Article submitted to Science, 1994 https://www.hq.nasa.gov/alsj/LRRR-94-0193.pdf.
[8] M. Schneider et al.: “Die Hochpräzisionsvermessung der Mond-bewegung,” web page of the Technical University of Munich, http://www.fesg.bv.tum.de/91872—fesg forschung llr.html→ web archive: http://web.archive.org/web/20170814125045/http://www.fesg.bv.tum.de/91872--~fesg~forschung~llr.html.
[9] B. Dasset et al, “méthode historique d'évaluation de la distance Terre-Lune et du diamètre de la Lune,“ 2005, http://eduscol.education.fr/bd/urtic/phy/?commande=aper&id=2156→ web archive: http://web.archive.org/web/20160304112759/http://eduscol.education.fr/bd/urtic/phy/?commande=aper&id=2156 then select the link to the presentation on top.
[10] New Scientist (No. 344) 20 June 1963, pages 672&673 https://books.google.ch/books?id=0hWpWSF7e7YC&hl=de Search for “laser moon”.
[11] T. W. Murphy et al., “APOLLO: the Apache Point Observatory Lunar Laser-ranging Operation: instrument description and first detections,” http://physics.ucsd.edu/~tmurphy/apollo/0710.0890v2.pdf, 2007.
[12] J. E. FALLER, FINAL REPORT, LASER RANGING RETRO-REFLECTOR EXPERIMENT, 1973 https://repository.hou.usra.edu/bitstream/handle/20.500.11753/842/31111000616431.pdf?sequence=1&isAllowed=y.
[13] TW Murphy, “Lunar laser ranging: the millimeter challenge”, https://tmurphy.physics.ucsd.edu/papers/rop-llr.pdf, 2013.
[14] C. Courde et al., “Lunar laser ranging in infrared at the Grasse laser station”, 2017 https://www.aanda.org/articles/aa/pdf/2017/06/aa28590-16.pdf.
[15] Toshimichi Otsubo et al., “Asymmetric dihedral angle offsets for largesize lunar laser ranging retroreflectors”, 2011 https://link.springer.com/article/10.5047/eps.2011.11.001.
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    Andreas Märki. (2020). A Critical Review of the Lunar Laser Ranging. American Journal of Astronomy and Astrophysics, 8(3), 39-44. https://doi.org/10.11648/j.ajaa.20200803.11

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    Andreas Märki. A Critical Review of the Lunar Laser Ranging. Am. J. Astron. Astrophys. 2020, 8(3), 39-44. doi: 10.11648/j.ajaa.20200803.11

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    Andreas Märki. A Critical Review of the Lunar Laser Ranging. Am J Astron Astrophys. 2020;8(3):39-44. doi: 10.11648/j.ajaa.20200803.11

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  • @article{10.11648/j.ajaa.20200803.11,
      author = {Andreas Märki},
      title = {A Critical Review of the Lunar Laser Ranging},
      journal = {American Journal of Astronomy and Astrophysics},
      volume = {8},
      number = {3},
      pages = {39-44},
      doi = {10.11648/j.ajaa.20200803.11},
      url = {https://doi.org/10.11648/j.ajaa.20200803.11},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ajaa.20200803.11},
      abstract = {This paper provides an overview of the Lunar Laser Ranging (LLR) experiments. The measurement principle is explained and its theory is derived. Both contributions, the direct reflected light from retroreflectors as well as the scattered light from the lunar surface are considered. The measurement results from the Sixties until 2007 are then compared between different LLR stations and with the theoretical forecast. The very first experiment was in 1962: a laser beam was directed to the Moon and the scattered light from the lunar surface was detected. The number of received photons was in line with the theory. Then from 1969 the laser beams were directed to retroreflectors placed by Apollo astronauts and Luna space crafts. Retroreflectors are on the one hand reference points for long term measurements; on the other hand they deliver a much stronger return signal compared to the scattered return. But none of the stations could measure the expected amplification of the retroreflectors. The number of received photons remained in line with measurements to the bare surface of the Moon. Therefore either all retroreflectors have degraded such that their return signals fit to the scattered return from the lunar soil or the measurements were indeed taken to the lunar surface only.},
     year = {2020}
    }
    

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    AB  - This paper provides an overview of the Lunar Laser Ranging (LLR) experiments. The measurement principle is explained and its theory is derived. Both contributions, the direct reflected light from retroreflectors as well as the scattered light from the lunar surface are considered. The measurement results from the Sixties until 2007 are then compared between different LLR stations and with the theoretical forecast. The very first experiment was in 1962: a laser beam was directed to the Moon and the scattered light from the lunar surface was detected. The number of received photons was in line with the theory. Then from 1969 the laser beams were directed to retroreflectors placed by Apollo astronauts and Luna space crafts. Retroreflectors are on the one hand reference points for long term measurements; on the other hand they deliver a much stronger return signal compared to the scattered return. But none of the stations could measure the expected amplification of the retroreflectors. The number of received photons remained in line with measurements to the bare surface of the Moon. Therefore either all retroreflectors have degraded such that their return signals fit to the scattered return from the lunar soil or the measurements were indeed taken to the lunar surface only.
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