Lunar laser ranging: The pointing error analysis to Lunokhod 1 and Lunokhod 2

Abstract

The corner-cube reflectors (CCRs) are small optical instruments designed to accurately measure the distance between the Earth and the Moon. Signals from L1 (Lunokhod 1) and L2 (Lunokhod 2) can be used for higher precision analysis of lunar libration than Apollo reflector. Here, we describe the optical performance of L1 and L2 at near-infrared wavelength. Theoretically, because of the initial direction and lunar librations, the surfaces of these arrays do not, in general, point directly to the Earth. The laser incident angles for the CCRs and the far-field diffraction patterns (FFDP) of individual CCRs of possible incident angles are calculated. Finally, extract the optical cross-section as a function of incident angles. In the experiment, for the first time, superconducting nanowire single-photon detectors (SNSPDs) at a wavelength of 1064 nm are designed and fabricated aiming at lunar laser ranging (LLR), and the effective echo rates of L1 and L2 are measured. Using experimental results to check the orientation of the CCRs. The experimental results show that there is an error in the initial pointing of the CCRs, the initial pointing angles of L1 and L2 are about from 10o to 40o.