Corner-cube retro-reflector instrument for advanced lunar laser ranging

Abstract

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.

Earth–Moon very-long-baseline interferometry project: modelling of the scientific outcome

“…It is recommended that the new radio telescope is colocated with a retroreflector, either a panel of cornercubes (Vasiliev et al 2014), or a next generation single cube retroreflector (Turyshev et al 2013;Araki et al 2016). Requiring no power on the Moon and no data transmission, the Earth-Moon laser ranging would help to determine the precise location of the station, and also independently contribute to study of lunar dynamics, and building of the lunar reference frame, and testing general relativity (Murphy 2013;Williams et al 2013b;Pavlov et al 2016;Viswanathan et al 2018).…”

Thermo-optical simulation and experiment for the assessment of single, hollow, and large aperture retroreflector for lunar laser ranging

“…html). Therefore, especially for the investigation of the lunar rotational variations, increasing normal point data from retroreflectors as far as possible from the A15 site (Turyshev et al 2013) is an important goal, in addition to the goal of increasing the range accuracy. Further, it is reported that the reflectivity of lunar reflectors shows degradation by a factor of 10 or more (Murphy et al 2010), which may affect data accuracy and productivity.…”

“…1). As for the reflection performance, the ray path difference in the A15 retroreflector is already ±7 cm [±1 (m) sin 8.2°] due to the array configuration and the optical (lunar orbital) libration, which is the main factor that limits range accuracy and peak value of returned pulse through the broadening of output laser pulse (Turyshev et al 2013). "Single-element retroreflector" (SERR) composed of a single corner-cube reflector made of a prism or three mirrors, which has no optical path difference in principle, is considered a solution to overcome these problems.…”

Scientific return of a lunar elevator

“…LSEI plans to use Single Cube Retroreflectors (SCR) as Laser ranging targets [29] for navigation during deployment of the LSE and the Landing Platform. The SCR would become a permanent addition to the Lunar Laser Ranging (LLR) retroreflector network.…”