MRRT: Modeling of multiple reflections of radiation between terrains
applied on the lunar surface region
Abstract
The lunar surface has a stable luminosity. To use the Moon as a
calibration standard, the Robotic Lunar Observatory (ROLO) program
models the integration of the radiance of the entire lunar surface.
However, the albedos of the mare and the highlands are very different.
The modeling based on the lunar global irradiance/reflected radiance is
bound to result in higher uncertainty. In contrast, if the local
calibration of the lunar surface is adopted, the lunar complex
topography effect cannot be ignored. This paper presents a new model for
quantifying multiple reflections of radiation between terrains (MRRT).
The relationship between the bidirectional reflectance factor (BRF) of
the observed pixel and the true microtopography reflectance is
established, which shows that the BRF is mainly influenced by the true
topography reflectance, the terrain undulation, the incident irradiance
on the topography surface, and the masking in the observation direction.
The new model applied on the lunar surface obtains clearer terrain
details. The inversion reflectance of the Chang’e-3 landing area is
closer to the reflectance measured in situ, and the reflectance curves
of the Apollo 16 landing area are almost consistent under different
illumination observation geometries. This shows that the MRRT model can
effectively eliminate the topographic effect. Compared with the ROLO
model, the MRRT model does not restrict the specific selection, so it
can select a region with a uniform material distribution, small albedo
difference, and low topography undulation to establish the lunar surface
radiometric calibration field with the advantage of providing stable
radiation characteristics.