Bibcode
Naranen, Jyri; Parviainen, Hannu; Muinonen, Karri; Josset, Jean-Luc; Beauvivre, Stephane; Koschny, Detlef; Foing, Bernard H.; Krieger, Bjoern; Amie Team
Referencia bibliográfica
37th COSPAR Scientific Assembly. Held 13-20 July 2008, in Montréal, Canada., p.2178
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2008
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Descripción
The Advanced Moon micro-Imager Experiment (AMIE) onboard the ESA SMART-1
lunar mission performed imaging of the Moon between November 2004 and
September 2006, when the mission was ended by crashing the spacecraft
into the lunar surface. AMIE was a 1024X1024 pixel miniaturized CCD
camera with three colour filters and a panchromatic channel (clear
filter). The images are of medium-to-high resolution, e.g. at 300 km
pericenter altitude the resolution was 27 m/pix. We selected four
different regions on the lunar surface imaged by AMIE for the
photometric investigation reported here. These regions were selected so
that as large phase angle coverage as possible was available, including
the opposition geometry. Each of the regions cover a few hundred square
kilometers of the lunar surface and were imaged by AMIE several tens of
times. The regions examined include, e.g., Reiner gamma and Oceanus
Procellarum near the crater Mairan. We utilized the latest in-flight
calibration data available and we also georetrified the images to
account for the aspect distortions. For the study reported here, the
panchromatic filter was chosen since it is the best calibrated channel
at the moment. The data was analyzed by implementing a numerical light
scattering model with which we have inverted the regolith porosity and
macroscopic surface roughness properties for the target areas. The model
computes the bidirectional reflectance function using the
geometric-optics approximation from a particulate medium constrained by
a self-affine fractal random fields mimicking the regolith-covered lunar
surface. Fractal description of the surface roughness is used, since it
gives a more realistic way to model the true macroscopic surface
roughness than the often used Gaussian correlation-model. Unlike in the
previous studies, the azimuthal shadowing effects are taken into
account, allowing for a more reliable inversion of surface statistics
from images with large phase angles. In addition, we have fitted an
empirical photometric function to the data which can be used to perform
photometric correction to the images in, e.g., image mosaicking. A
comparison with the results from the relevant previous photometric
studies of the Moon is given. We end by presenting plans for future
studies, especially the possible multi-colour photometry.