Until 29 May 2020, the Visible and Near-Infrared Imaging Spectrometer (VNIS) onboard the Yutu-2 Rover of the Chang'e-4 (CE-4) has acquired 96 high-resolution surface in-situ imaging spectra. These spectra were acquired under different illumination conditions, thus photometric normalization should be conducted to correct the introduced albedo differences before deriving the quantitative mineralogy for accurate geologic interpretations. In this study, a Lommel-Seeliger (LS) model and Hapke radiative transfer (Hapke) model were used and empirical phase functions of the LS model were derived. The values of these derived phase functions exhibit declining trends with the increase in phase angles and the opposition effect and phase reddening effect were observed. Then, we discovered from in-situ and laboratory measurements that the shadows caused by surface roughness have significant impacts on reflectance spectra and proper corrections were introduced. The validations of different phase functions showed that the maximum discrepancy at 1500 nm of spectra corrected by the LS model was less (similar to 3.7%) than that by the Hapke model (similar to 7.4%). This is the first time that empirical phase functions have been derived for a wavelength from 450 to 2395 nm using in-situ visible and near-infrared spectral datasets. Generally, photometrically normalized spectra exhibit smaller spectral slopes, lower FeO contents and larger optical maturity parameter (OMAT) than spectra without correction. In addition, the band centers of the 1 and 2 mu m absorption features of spectra after photometric normalization exhibit a more concentrated distribution, indicating the compositional homogeneity of soils at the CE-4 landing site.
Publication name |
REMOTE SENSING Volume: 12 Issue: 19 Article Number: 3211 DOI: 10.3390/rs12193211 Published: OCT 2020 |
Author(s) |
Qi, Xiaobin; Ling, Zongcheng; Zhang, Jiang; Chen, Jian; Cao, Haijun; Liu, Changqing; Qiao, Le; Fu, Xiaohui; He, Zhiping; Xu, Rui; Liu, Jianzhong; Zou, Yongliao |
Corresponding author(s) |
LING Zongcheng zcling@sdu.edu.cn -Shandong Univ, Inst Space Sci, Sch Space Sci & Phys, Shandong Key Lab Opt Astron & Solar Terr Environm, Weihai 264209, Peoples R China. -Chinese Acad Sci, CAS Ctr Excellence Comparat Planetol, Hefei 230026, Peoples R China. |
Author(s) from IGCAS |
LIU Jianzhong | View here for the details
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