The Effects of Viewing Geometry on the Spectral Analysis of Lunar Regolith as Inferred by <i>in situ</i> Spectrophotometric Measurements of Chang'E‐4

Yang, Yazhou; Lin, Honglei; Liu, Yang; Lin, Yangting; Wei, Yong; Hu, Sen; Yang, Wei; Xu, Rui; He, Zhiping; Zou, Yongliao

doi:10.1029/2020gl087080

Cited by 26 publications

(21 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Based on the unique in situ spectral data obtained by VNIS, we have gained more information about the origin and evolution of the moon and space weathering [1,31,[41][42][43][44][45][46][47][48][49][50][51][52][53]. Li et al further analyzed the REFF spectra collected by VNIS on the first lunar day.…”

Section: Application Results Of Vnis On Board Chang'e-4mentioning

confidence: 99%

Applications of AOTF Spectrometers in In Situ Lunar Measurements

Gui

et al. 2021

Materials

Self Cite

View full text Add to dashboard Cite

Spectrometers based on acousto-optic tunable filters (AOTFs) have several advantages, such as stable temperature adaptability, no moving parts, and wavelength selection through electrical modulation, compared with the traditional grating and Fourier transform spectrometers. Therefore, AOTF spectrometers can realize stable in situ measurement on the lunar surface under wide temperature ranges and low light environments. AOTF imaging spectrometers were first employed for in situ measurement of the lunar surface in the Chinese Chang’e project. The visible and near-infrared imaging spectrometer and the lunar mineralogical spectrometer have been successfully deployed on board the Chang’e-3/4 and Chang’e-5 missions. In this review, we investigate the performance indicators, structural design, selected AOTF performance parameters, data acquisition of the three lunar in situ spectral instruments used in the Chang’e missions. In addition, we also show the scientific achievement of lunar technology based on in situ spectral data.

show abstract

Section: Application Results Of Vnis On Board Chang'e-4mentioning

confidence: 99%

Applications of AOTF Spectrometers in In Situ Lunar Measurements

Gui

et al. 2021

Materials

Self Cite

View full text Add to dashboard Cite

show abstract

“…As shown in Figure 5c, similar to CE-4 VNIS spectra corrected by the Hapke model (mentioned in Section 3.1), the normalized laboratory spectra employing the Hapke model exhibit a similar dispersion. This may further enhance our recognition that the parameters (b = −0.4 and c = 0.25) in the phase functions of the Hapke model are not reliable when applying it to the CE-4 VNIS spectra [31]. Instead, we would use the phase function parameters (b = −0.17 and c = 0.70, named by YZ parameters in this work) of the Hapke model obtained by CE-4 in-situ measurements [31] to normalize the CE-4 REFF spectra at different phase angles.…”

Section: Laboratory Spectral Measurements Of Lunar Regolith Analogmentioning

confidence: 90%

“…The Hapke radiative transfer (Hapke) model is based on the radiative transport equation of granular media and comprehensively considers the effects of mineralogy, surface roughness, grain sizes, compaction, and multiple scattering factors [9,11,22,23]. This model has been widely applied to the photometric normalization of reflectance spectra detected from various solar system objects (e.g., asteroids, Mercury, comets, Mars, Moon) [12,[24][25][26][27][28][29][30][31].…”

Section: Vnis Instrumentmentioning

confidence: 99%

“…However, due to the limited observation data on the fourth lunar day, the derived phase functions only cover the spectral ranges of 470-945 nm [21]. Using the Hapke model, Yang et al [31] and Lin et al [38] evaluated the effect of view geometry on CE-4 spectral data and derived average Hapke parameters for the potential uses of a Legendre pronominal and Henyey-Greenstein single-scattering phase functions in the Hapke model.…”

Section: Vnis Instrumentmentioning

confidence: 99%

See 1 more Smart Citation

Photometric Normalization of Chang’e-4 Visible and Near-Infrared Imaging Spectrometer Datasets: A Combined Study of In-Situ and Laboratory Spectral Measurements

Ling

Zhang

et al. 2020

Remote Sensing

Self Cite

View full text Add to dashboard Cite

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 (~3.7%) than that by the Hapke model (~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 μm absorption features of spectra after photometric normalization exhibit a more concentrated distribution, indicating the compositional homogeneity of soils at the CE-4 landing site.

show abstract

“…The CE-4 VNIS is installed at the front of the Yutu-2 rover at a height of approximately 0.7 m, looking down at the lunar surface at 45 • , as shown in Figure 2. The size of the observation area is ∼15 × 21 cm [14]. The device contains two channels: a VIS/NIR channel and a short-wave infrared (SWIR) channel.…”

Section: Chang'e-4 Spectral Data and Preprocessingmentioning

confidence: 99%

Effect of Lunar Complex Illumination on In Situ Measurements Obtained Using Visible and Near-Infrared Imaging Spectrometer of Chang’E-4

Wang

Lin

et al. 2021

Remote Sensing

Self Cite

View full text Add to dashboard Cite

In-situ measurements of the spectral information on the lunar surface are of significance to study the geological evolution of the Moon. China’s Chang’E-4 (CE-4) Yutu-2 rover has conducted several in-situ spectral explorations on the Moon. The visible and near-infrared imaging spectrometer (VNIS) onboard the rover has acquired a series of in-situ spectra of the regolith at the landing site. In general, the mineralogical research of the lunar surface relies on the accuracy of the in-situ data. However, the spectral measurements of the Yutu-2 rover may be affected by shadows and stray illumination. In this study, we analyzed 106 CE-4 VNIS spectra acquired in the first 24 lunar days of the mission and noted that six of these spectra were affected by the shadows of the rover. Therefore, a method was established to correct the effects of the rover shadow on the spectral measurements. After shadow correction, the FeO content in the affected area is corrected to 14.46 wt.%, which was similar to the result calculated in the normal regolith. Furthermore, according to the visible images, certain areas of the explored sites were noted to be unusually bright. Considering the reflectance, geometric information, and shining patterns of the multi-layer insulation (MLI), we examined the influence of the specular reflection of the MLI on the bright spot regionsd , and found that the five sets of data were likely not affected by the specular reflection of the MLI. The results indicated that the complex illumination considerably influences the in situ spectral data. This study can provide a basis to analyze the VNIS scientific data and help enhance the accuracy of interpretation of the composition at CE-4 landing sites.

show abstract

The Effects of Viewing Geometry on the Spectral Analysis of Lunar Regolith as Inferred by in situ Spectrophotometric Measurements of Chang'E‐4

Cited by 26 publications

References 36 publications

Applications of AOTF Spectrometers in In Situ Lunar Measurements

Applications of AOTF Spectrometers in In Situ Lunar Measurements

Photometric Normalization of Chang’e-4 Visible and Near-Infrared Imaging Spectrometer Datasets: A Combined Study of In-Situ and Laboratory Spectral Measurements

Effect of Lunar Complex Illumination on In Situ Measurements Obtained Using Visible and Near-Infrared Imaging Spectrometer of Chang’E-4

Contact Info

Product

Resources

About