Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

We investigated six bright swirls associated with magnetic anomalies of variable strength using Chandrayaan-1 Moon Mineralogy Mapper (M3) hyperspectral image data. We examined the 3 μm absorption band generally ascribed to solar wind-induced OH/H2O and spectral trends in the near-infrared wavelength range at on-swirl and off-swirl locations. We found that the 3 μm absorption band is weaker at on-swirl than at off-swirl locations and shows only weak variations with time-of-day. This result is consistent with magnetic anomaly shielding that reduces solar wind interaction with the surface. For a small swirl structure in Mare Moscoviense, we found the 3 μm absorption band to be similar to that of its surroundings due to the absence of strong magnetic shielding. Our spectral analysis results at on-swirl and off-swirl locations suggest that the spectral trends at on-swirl and off-swirl locations cannot always be explained by reduced space-weathering alone. We propose that a combination of soil compaction possibly resulting from the interaction between the surface and cometary gas and subsequent magnetic shielding is able to explain all observed on-swirl vs. off-swirl spectral trends including the absorption band depth near 3 μm. Our results suggest that an external mechanism of interaction between a comet and the uppermost regolith layer might play a significant role in lunar swirl formation.

Download Full-text

Cirrus cloud optical and microphysical property retrievals from eMAS during SEAC<sup>4</sup>RS using bi-spectral reflectance measurements within the 1.88  µm water vapor absorption band

Atmospheric Measurement Techniques ◽

10.5194/amt-9-1743-2016 ◽

2016 ◽

Vol 9 (4) ◽

pp. 1743-1753 ◽

Cited By ~ 7

Author(s):

Kerry Meyer ◽

Steven Platnick ◽

G. Thomas Arnold ◽

Robert E. Holz ◽

Paolo Veglio ◽

...

Keyword(s):

Water Vapor ◽

Absorption Band ◽

Near Infrared ◽

Single Layer ◽

Distinct Advantage ◽

Cirrus Cloud ◽

Water Vapor Absorption ◽

Cloud Particle ◽

Infrared Wavelength ◽

Vapor Absorption

Abstract. Previous bi-spectral imager retrievals of cloud optical thickness (COT) and effective particle radius (CER) based on the Nakajima and King (1990) approach, such as those of the operational MODIS cloud optical property retrieval product (MOD06), have typically paired a non-absorbing visible or near-infrared wavelength, sensitive to COT, with an absorbing shortwave or mid-wave infrared wavelength sensitive to CER. However, in practice it is only necessary to select two spectral channels that exhibit a strong contrast in cloud particle absorption. Here it is shown, using eMAS observations obtained during NASA's SEAC4RS field campaign, that selecting two absorbing wavelength channels within the broader 1.88 µm water vapor absorption band, namely the 1.83 and 1.93 µm channels that have sufficient differences in ice crystal single scattering albedo, can yield COT and CER retrievals for thin to moderately thick single-layer cirrus that are reasonably consistent with other solar and IR imager-based and lidar-based retrievals. A distinct advantage of this channel selection for cirrus cloud retrievals is that the below-cloud water vapor absorption minimizes the surface contribution to measured cloudy top-of-atmosphere reflectance, in particular compared to the solar window channels used in heritage retrievals such as MOD06. This reduces retrieval uncertainty resulting from errors in the surface reflectance assumption and reduces the frequency of retrieval failures for thin cirrus clouds.

Download Full-text

Near Infrared Hyperspectral Imaging in Transmission Mode: Assessing the Weathering of Thin Wood Samples

Journal of Near Infrared Spectroscopy ◽

10.1255/jnirs.1253 ◽

2016 ◽

Vol 24 (6) ◽

pp. 595-604 ◽

Cited By ~ 9

Author(s):

Knut Arne Smeland ◽

Kristian Hovde Liland ◽

Jakub Sandak ◽

Anna Sandak ◽

Lone Ross Gobakken ◽

...

Keyword(s):

Solar Radiation ◽

Near Infrared ◽

Prediction Models ◽

Hyperspectral Image ◽

Principal Component Regression ◽

Principal Component ◽

Transmission Mode ◽

Infrared Wavelength ◽

Robust Prediction ◽

Wooden Surface

Untreated wooden surfaces degrade when exposed to natural weathering. In this study thin wood samples were studied for weather degradation effects utilising a hyperspectral camera in the near infrared wavelength range in transmission mode. Several sets of samples were exposed outdoors for time intervals from 0 days to 21 days, and one set of samples was exposed to ultraviolet (UV) radiation in a laboratory chamber. Spectra of earlywood and latewood were extracted from the hyperspectral image cubes using a principal component analysis-based masking algorithm. The degradation was modelled as a function of UV solar radiation with four regression techniques, partial least squares, principal component regression, Ridge regression and Tikhonov regression. It was found that all the techniques yielded robust prediction models on this dataset. The result from the study is a first step towards a weather dose model determined by temperature and moisture content on the wooden surface in addition to the solar radiation.

Download Full-text

Cirrus cloud optical and microphysical property retrievals from eMAS during SEAC<sup>4</sup>RS using bi-spectral reflectance measurements within the 1.88 μm water vapor absorption band

10.5194/amt-2015-326 ◽

2016 ◽

Author(s):

K. Meyer ◽

S. Platnick ◽

G. T. Arnold ◽

R. E. Holz ◽

P. Veglio ◽

...

Keyword(s):

Water Vapor ◽

Absorption Band ◽

Near Infrared ◽

Single Layer ◽

Distinct Advantage ◽

Cirrus Cloud ◽

Water Vapor Absorption ◽

Cloud Particle ◽

Infrared Wavelength ◽

Vapor Absorption

Abstract. Previous bi-spectral imager retrievals of cloud optical thickness (COT) and effective particle radius (CER) based on the Nakajima and King (1990) approach, such as those of the operational MODIS cloud optical property retrieval product (MOD06), have typically paired a non-absorbing visible or near-infrared wavelength, sensitive to COT, with an absorbing shortwave or midwave infrared wavelength sensitive to CER. However, in practice it is only necessary to select two spectral channels that exhibit a strong contrast in cloud particle absorption. Here it is shown, using eMAS observations obtained during NASA's SEAC4RS field campaign, that selecting two absorbing wavelength channels within the broader 1.88 μm water vapor absorption band, namely the 1.83 and 1.93 μm channels that have sufficient differences in ice crystal single scattering albedo, can yield COT and CER retrievals for thin to moderately thick single-layer cirrus that are reasonably consistent with other solar and IR imager-based and lidar-based retrievals. A distinct advantage of this channel selection for cirrus cloud retrievals is that the surface contribution to measured cloudy TOA reflectance is minimized due to below-cloud water vapor absorption, thus reducing retrieval uncertainty resulting from errors in the surface reflectance assumption, as well as reducing the frequency of retrieval failures for thin cirrus clouds.

Download Full-text

SEASONAL SPECTRAL SEPARABILITY OF SELECTED GRASSES: CASE STUDY FROM THE KRKONOŠE MTS. TUNDRA ECOSYSTEM

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xliii-b3-2020-371-2020 ◽

2020 ◽

Vol XLIII-B3-2020 ◽

pp. 371-376

Author(s):

L. Červená ◽

L. Kupková ◽

M. Potůčková ◽

J. Lysák

Keyword(s):

Near Infrared ◽

Hyperspectral Image ◽

Single Layer ◽

Image Data ◽

Nardus Stricta ◽

Spectral Bands ◽

Tundra Ecosystem ◽

Leaf Level ◽

Spectral Separability ◽

June July

Abstract. This paper focuses on spectral separability of closed alpine grasslands dominated with Nardus stricta and competitive grasses Calamagrostis villosa and Molinia caerulea in the relict arctic-alpine tundra located in the Krkonoše Mountains National Park, Czech Republic. The spectral data were acquired and compared at three levels: spectra of a single layer of leaves measured with the ASD FieldSpec4 Wide-Res spectroradiometer coupled with a contact probe in a laboratory (leaf level), canopy spectra measured in a field with the same spectroradiometer using the fiber optic cable with a pistol grip (canopy level), and hyperspectral image data acquired by Nano-Hyperspec® fastened to the DJI Matrice 600 Pro drone (image level). All the measurements were repeated three times during the 2019 vegetation season – in June, July and August. Using the methods of analysis of variance and Welch's (unpaired) t-test, it was proven that there were differences in the results for all three spectra sources. But in general, for each combination of species and each data source a suitable date and intervals of the spectral bands for species separation exist. The most suitable term for data acquisition in order to differentiate all the species is July. At the leaf level, the best species separability was observed in the near-infrared and shortwave infrared spectral ranges. At the canopy and image levels, the visible bands are of higher importance for discriminating the species.

Download Full-text

Dependence of the Hydration of the Lunar Surface on the Concentrations of TiO2, Plagioclase, and Spinel

Remote Sensing ◽

10.3390/rs14010047 ◽

2021 ◽

Vol 14 (1) ◽

pp. 47

Author(s):

Marcel Hess ◽

Christian Wöhler ◽

Alexey A. Berezhnoy ◽

Janice L. Bishop ◽

Vladislav V. Shevchenko

Keyword(s):

Solar Wind ◽

Spectral Properties ◽

Lunar Regolith ◽

Daily Basis ◽

Time Of Day ◽

Low Energy ◽

The Moon ◽

High Concentration ◽

Highly Correlated ◽

Band Depth

We investigate the interrelation between the hydration of the lunar regolith and the mineral composition of the surface of the Moon with respect to the concentrations of plagioclase, TiO2 (highly correlated with the oxide mineral ilmenite), and Mg-spinel. The spectral properties of lunar regions with a low concentration of plagioclase or a high concentration of TiO2 or Mg-spinel show a significant reduction in hydration at lunar midday compared to other compositions. This suggests that these oxide minerals contain less of the strongly bound OH component, which is not removed at lunar midday. The time-of-day-dependent variation of the 3 μm band depth is greater in TiO2-rich areas compared to other mare regions. The TiO2-rich regions therefore appear to have a strong tendency to adsorb solar wind-induced hydrogen into binding states of low energy that can more readily desorb and readsorb OH/H2O on a daily basis.

Download Full-text