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Lunar Laser Ranging: Description, Results and the Future

Event Details

Event Dates: 

Friday, April 13, 2012 - 6:00am

Speaker Name(s): 

Doug Currie

Speaker Affiliation(s): 

University of Maryland
Seminar Type/Subject

Event Details & Abstract: 

Lunar Laser Ranging to the retroreflecting mirrors left on the lunar surface continue to this day to operate and generate new science results. The basic experimental process and the unique science results addressing the physics of the lunar interior and gravitational science that have been produced by the Lunar Laser Ranging Program (LLRP) to date will be described. While the Apollo retroreflector arrays are still operation and continue to produce new state-of-the-art science results, the combination of the lunar librations and the design of the arrays currently limit the range accuracy obtained for each single photo-electron return to ~20 mm. A next generation lunar retroreflector (e.g., the Lunar Laser Ranging Retroreflector for the 21st Century or LLRRA-21) holds promise for great improvements in the existing science results. This is critical due to the need to better understand the deep interior of the moon, which addresses the origin of the solar system bodies. On the other hand, the gravitational observations are important due to the inconsistency between General Relativity and Quantum Mechanics. The magnitude of these improvements will depend critically on the method of robotic deployment of the LLRRA-21. The deployment will be reviewed, especially those that can be supported by the Google Lunar X Prize flights of the next few years. The expected magnitude of the return signal derived from the optical/thermal simulations will be described. This expected signal return will be similar to signal return that is currently being obtained from the Apollo 15 array, so we can evaluate the capability of various ground stations to conduct regular ranging programs. This will address the number of ground stations that can contribute and the frequency of observations what would be available for the science analysis. Finally, the lifetime issues related to the Apollo arrays and the projection to the current design of the LLRRA-21 will be discussed. This work has been supported by the LUNAR team of the NASA/NLSI and the INFN-LNF and ASI.