New Method of Photometric Correction for Lunar Uvvis Images

Introduction: An accurate phase function is necessary for precise photometric correction of the Clementine lunar UVVIS images. Although several researchers have proposed photometric models for Clementine UVVIS images using empirical phase functions (e.g., [1] [2] [3]), additional work is required for correction of the data at small phase angle (<20), because the phase function at small phase angle is significantly dependent on both the wavelengths and the geology. We propose the iterative method of photometric correction, in which automatic clustering of multi-band spectrum by Self-Organizing Map (SOM) [4] method, and determination of phase function for each spectral group are successively performed. Basic Photometric model: Viewing geometry at lunar surface is specified with three angles: incidence angle i, emission angle e, and phase angle α, and i=30, e=0, and α=30 are generally employed as the standard viewing geometry. We employed the lunar photometric model expressed by ( ) ) ( ) , , ( , ) , , ; , ( , , 30 α α α λ λ λ λ k F e i D y x R C e i y x I = , (1)