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Photometric observations of Titan since 1972 show a cyclical variation of ≡10%. A minimum value of brightness and albedo apparently occurred in 1984. Spectrophotometric observations, made annually since 1980 at 8 Å resolution, 3295 - 8880 Å, were used to derive the value p* = 0.156±0.010 for integrated geometric albedo in 1984. Variations of the equivalent widths of spectral features were not seen.
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Lockwood et al. (1986) studied this question.
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