Design and optimization of dihedral angle offsets for the next generation lunar retro-reflectors

TL;DR

This paper explores the design and optimization of dihedral angle offsets in next-generation lunar retro-reflectors to enhance laser ranging accuracy, supported by empirical measurements of prototype reflectors.

Contribution

It introduces a novel design approach for lunar retro-reflectors with optimized dihedral angle offsets, validated through experimental measurements.

Findings

Optimized dihedral angles improve ranging accuracy.

Prototype reflectors demonstrate reduced angular velocity offset effects.

Design principles enhance lunar laser ranging precision.

Abstract

Lunar laser ranging (LLR) to the Apollo retro-reflectors, which features the most long-lasting experiment in testing General Relativity theories, has remained operational over the past four decades. To date, with significant improvement of ground observatory conditions, the bottleneck of LLR accuracy lies in the retro-reflectors. A new generation of large aperture retro-reflectors with intended dihedral angle offsets have been suggested and implemented based on NASA's recent lunar projects to reduce its ranging uncertainty to be less than 1.0 mm. The technique relies on the retro-reflector's ability to offset its relative angular velocity with regard to a ground LLR observatory (LLRO), so that the LLR accuracy can be ensured along with the larger area of beam reflection. In deployment, solid corner-cube reflectors (CCRs) based on empirical successes of the Apollo 11 and 15 arrays have been selected for the next generation lunar reflectors (NGLRs) due to their stability against heat and dust problems on the Moon. In this work, we present the optical effects in designing the new retro-reflectors given various sets of intended diheral angle offsets (DAOs), and support the design principles with the measurements of of two manufactured NGLRs.