# Lunar laser ranging in infrfared at hte Grasse laser station

## TL;DR

This paper presents the implementation of infrared lunar laser ranging at the Grasse station, which improves observation density, homogeneity, and efficiency, especially during full Moon periods, and reveals new insights into lunar retro-reflector performance.

## Contribution

It introduces infrared detection for lunar laser ranging at Grasse, enhancing measurement density, homogeneity, and efficiency, and provides new data on Lunokhod 2 performance.

## Key findings

- Infrared detection densifies lunar observations.
- Infrared telemetry enables measurements during full Moon periods.
- Lunokhod 2 efficiency matches Lunokhod 1 with infrared link.

## Abstract

For many years, lunar laser ranging (LLR) observations using a green wavelength have suffered an inhomogeneity problem both temporally and spatially. This paper reports on the implementation of a new infrared detection at the Grasse LLR station and describes how infrared telemetry improves this situation. Our first results show that infrared detection permits us to densify the observations and allows measurements during the new and the full Moon periods. The link budget improvement leads to homogeneous telemetric measurements on each lunar retro-reflector. Finally, a surprising result is obtained on the Lunokhod 2 array which attains the same efficiency as Lunokhod 1 with an infrared laser link, although those two targets exhibit a differential efficiency of six with a green laser link.