Selenology Today # 7 July 2007 - Home

Figure 2-4a
GEOLOGIC LUNAR RESEARCH SELENOLOGY TODAY # 7
The derivative matched filter algorithm
is quite similar to the matched filter
algorithm, however, the match is made to
the first derivative of the reflectance
spectrum. As discussed in Part I of this
paper, derivative spectra can be useful in
better distinguishing mixtures of
minerals having overlapping peaks.
Figure 2-5a shows the results of a
derivative matched filter algorithm
applied to the same pixel group on the
floor of Bullialdus that was defined
above. A strong correlation is shown by
darker greyscale values.
Figure 2-5a
page 18
Part 3. Calibration of User
Created Lunar Multiband Images
The Clementine calibrated UVVIS/NIR
images provide tremendous spatial
resolution, but some amateurs may want to
create their own multiband images by
using broadfilters with small telescopes.
This section discusses how to calibrate
such images and use them for the same
types of analyses that were outlined above
for Clementine calibrated images.
This section attempts a relative
calibration of five band spectral images
taken through a small telescope and
compares the results with Clementine
reflectance data. The method used is based
upon use of the Apollo 16 site and Apollo
16 laboratory speciman 62231 as
calibration standards. There is no attempt
to achieve an absolute calibration of the
five filter images by either correcting for
phase angles outside of the 20 to 50
degree range in which reflectance values
agree reasonably well with the standard
geometry used by Clementine, or by
correcting the photometric function for
lunar curvature effects that are present to
some extent in the telescopic five filter
images. The results of the relative
calibration are compared to Clementine
false color and ratio images.
Introduction
The Clementine orbiter took a series of
UVVIS and NIR filter images of the lunar
surface. These images were obtained at
standard geometry (i.e. bidirectional
reflectance with e=30 degrees and i=0
degrees). It took professional astronomers
years to achieve an absolute calibration of
these filter images. The absolute
calibration addressed not only radiometric
and photometric considerations but also