Geoscience Reference
In-Depth Information
The mineral mapping of the lunar surface can be broadly subdivided into global
and regional mineral mapping. The regional mineral mapping concentrates on some
important locations of mare and highland region where the drastic mineral composi-
tional changes exist (Staid and Pieters
2000
; LeMouélic et al.
1999
; LeMouélic and
Langevin
2001
; Pieters et al.
2001
). The purpose of mineral mapping is efficient
lunar resource utilization, which requires accurate and quantitative evaluation of
mineral and glass abundances, distribution, and extraction feasibility, especially
for ilmenite. Common rock-forming minerals exhibit wavelength-dependent spec-
tral features throughout the VNIR (0.4-1.0 m), SWIR (1.0-2.5 m), and TIR
(5-25 m) wavelength ranges.
The linear spectral unmixing is an efficient tool to quantify the materials
distributed in the image. The spectral unmixing tool is used to decompose a
reflectance (or corrected radiance) source spectrum into a set of given end-member
spectra. The result of the unmixing is a measure of the membership of the individual
end-member to the source spectrum. Linear unmixing has proven to be the most
efficient algorithm to separate spectral fingerprints in hyperspectral images, but it
requires known reference for giving input to match the spectra called end-member
spectra for all of the probes present in the image. In general terms, linear unmixing
is currently the most powerful technique for matching the spectral variations and
establishing the quantitative mapping. It is often the case in remote sensing, that
one wants to deal with identification, detection, and quantification of fractions of
the target materials for each pixel for diverse coverage in a region using unmixing
approaches to discern the proportion of heterogeneity (Kanniah et al.
2001
). Linear
mixture modeling assumes that the signal received by the satellite sensor depends on
the proportion of individual surface components during the mixing process, such as
soil, water, and vegetation present in a particular pixel (Abdul
2003
). The unmixing
decomposes a mixed pixel into a collection of end-members and a set of fractional
abundances that indicate the proportion of each end-member available in the images.
The contribution of each pixel is assigned to the percentage of area each ground
cover class occupies in the pixel (Boardman
1989
).
2.2
Study Area
In the present study, the basaltic regions of the Orientale basins such as Mare
Orientale South's central part centered at 21.3
0
S and 265.4
0
E, Lacus Veris' central
part located at 14
ı
S and 273
ı
E, and the main portion of the Lacus Autumni
centered at 12
ı
S and 277.5
0
E test sites are selected for carrying out the analysis.
The following criteria were taken in mind to select the Orientale basin as the study
area; Mare Orientale (the “eastern sea”) is one of the most striking lunar features
on a large scale. Since the Orientale basin has not been sampled by the Apollo
program, the basin's precise age is not known. Unlike most other basins on the
Moon, Orientale is relatively less flooded by mare basalts and exposes much of the
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