Photometric properties of lunar regolith revealed by the Yutu-2 rover

¹ Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, PR China
e-mail: linyt@mail.iggcas.ac.cn
² State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, PR China
e-mail: yangliu@nssc.ac.cn
³ Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei 230026, PR China
⁴ Department of Earth Sciences, University of Hawai‘i at Mānoa, Honolulu, HI, USA
⁵ State key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100101, PR China
⁶ Key Laboratory of Space Active Opto-Electronics Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, PR China
⁷ Beijing Aerospace Control Center, Beijing 100094, PR China
⁸ Beijing Institute of Control Engineering, Beijing 100094, PR China

Received: 1 March 2020
Accepted: 29 April 2020

Abstract

Context. The surface composition of the Moon has mainly determined based on the visible and near-infrared spectra achieved from orbits and/or landing sites, and the spectroscopic analysis is based on photometric properties of the topmost lunar regolith. However, the lack of a ground truth for the photometric parameters of the undisturbed lunar surface has limited accurate applications of spectral observations.

Aims. Here we report the photometric properties of the small-scale (i.e., centimeter level) undisturbed lunar regolith around the Chang’E-4 landing site, determined from a series of photometric experiments conducted by the rover Yutu-2.

Methods. The simplified Hapke model was used to derive the photometric properties. The micro-topographic effect on the spectral measurements was corrected for the first time in the in situ photometric investigations on the Moon, which improves the accuracy of the derived photometric parameters.

Results. The single-scattering albedo w and two parameters (b, c) of the Henyey-Greenstein phase function were derived, and they show a wavelength dependence. The regolith at the Chang’E-4 landing site exhibits strong forward scattering according to the retrieved c values, and the higher asymmetry parameter indicates that the regolith here is more strongly forward scattering than the Apollo lunar soil samples. The derived photometric parameters can serve as ground truth and can be used in the radiative transfer modeling analysis of the orbital remote-sensing data.