Opposition effect in the brightness of celestial bodies as a diagnostic factor

1Shkuratov, Yu.G, 2Kreslavskiy, MA, 2Ovcharenko, AA, 3Muinonen, K, 4Piironen, J, 5Karttunen, H
1Institute of Astronomy of V. N. Karazin National University of Kharkiv, Kharkiv, Ukraine; Institute of Radio Astronomy of the National Academy of Sciences of Ukraine, Kharkiv, Ukraine
2Institute of Astronomy of V.N. Karazin National University of Kharkiv, Kharkiv, Ukraine
3Observatory of the University of Helsinki, Helsinki, Finland; Astronomical Observatory of the Uppsala University, Uppsala, Sweden
4Astronomical Observatory of the Uppsala University, Sweden; Science Center Institute of Space Research, Ispra, Italy
5Tuorla observatory, Finland
Kosm. nauka tehnol. 1998, 4 ;(1):54–59
Publication Language: Russian
Results of studies of the lunar opposition effect from the Clementine data are presented. The amplitude of the effect is shown to be 10 % in the phase angle range 0-1 degrees. Some leveling down of phase curves at phase angles < 0.5 degree is observed owing to a finite angular size of the Sun. The opposition effect of natural show surfaces has also been studied. A prominent brightness spike is found only for surfaces was studied, and dirty snow samples were found to have a distinct peak and phase angles from 0.2 to 5.0 degrees. Optical characteristics of structure analogs of planetary regoliths were measured by a laboratory photometer-polarimeter at phase angles 0.2-3.5 degrees. It is shown that: (1) the width of opposition spikes depends significantly on size of scattering surface particles, (2) a contribution from the coherent backscatter enhancement is well detected even for surface with an albedo of about 10 %.
Keywords: Clementine, lunar opposition effect, Moon
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