TY - JOUR
T1 - Galileo photometry of asteroid 243 Ida
AU - Helfenstein, P.
AU - Veverka, J.
AU - Thomas, P. C.
AU - Simonelli, D. P.
AU - Klaasen, K.
AU - Johnson, T. V.
AU - Fanale, F.
AU - Granahan, J.
AU - McEwen, A. S.
AU - Belton, M.
AU - Chapman, C.
N1 - Funding Information:
Special thanks to R. Binzel and D. Tholen for generously providing telescopic data. Brian Carcich and Lisa Wainio provided essential technical assistance and Mary Roth helped in manuscript preparation. We thank Mark Sykes and Paul Johnson for invaluable critiques and suggestions. This study was supported by the Galileo Project and by NASA Grants NAGW-2451 and NAGW-2186.
PY - 1996/3
Y1 - 1996/3
N2 - Galileo imaging observations over phase angles 19.5° to 109.8° are combined with near-opposition Earth-based data to derive the photometric properties of Ida. To first order these properties are uniform over the surface and well modeled at λ = 0.55 μm by Hapke parameters ω̃0 = 0.22, h = 0.020, B0 = 1.5, g = -0.33, and θ = 18° with corresponding geometric albedo p = 0.21±0.030.01 and Bond albedo AB = 0.081±0.0170.008. Ida's photometric properties are more similar to those of "average S-asteroids" (P. Helfenstein and J. Veverka 1989, Asteroids II, Univ. of Arizona Press, Tucson) than are those of 951 Gaspra. Two primary color units are identified on Ida: Terrain A exhibits a spectrum with relatively shallower 1-μm absorption and a relatively steeper red spectral slope than average Ida, while Terrain B has a deeper 1-μm absorption and a less steep red slope. The average photometric properties of Ida and Terrain A are similar while those of Terrain B differ mostly in having a slightly higher value of ω̃0 (0.22 versus 0.21), suggesting that Terrain B consists of slightly brighter, more transparent regolith particles. Galileo observations of Ida's satellite Dactyl over phase angles 19.5° to 47.6° suggest photometric characteristics similar to those of Ida, the major difference being Dactyl's slightly lower albedo (0.20 compared to 0.21).
AB - Galileo imaging observations over phase angles 19.5° to 109.8° are combined with near-opposition Earth-based data to derive the photometric properties of Ida. To first order these properties are uniform over the surface and well modeled at λ = 0.55 μm by Hapke parameters ω̃0 = 0.22, h = 0.020, B0 = 1.5, g = -0.33, and θ = 18° with corresponding geometric albedo p = 0.21±0.030.01 and Bond albedo AB = 0.081±0.0170.008. Ida's photometric properties are more similar to those of "average S-asteroids" (P. Helfenstein and J. Veverka 1989, Asteroids II, Univ. of Arizona Press, Tucson) than are those of 951 Gaspra. Two primary color units are identified on Ida: Terrain A exhibits a spectrum with relatively shallower 1-μm absorption and a relatively steeper red spectral slope than average Ida, while Terrain B has a deeper 1-μm absorption and a less steep red slope. The average photometric properties of Ida and Terrain A are similar while those of Terrain B differ mostly in having a slightly higher value of ω̃0 (0.22 versus 0.21), suggesting that Terrain B consists of slightly brighter, more transparent regolith particles. Galileo observations of Ida's satellite Dactyl over phase angles 19.5° to 47.6° suggest photometric characteristics similar to those of Ida, the major difference being Dactyl's slightly lower albedo (0.20 compared to 0.21).
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U2 - 10.1006/icar.1996.0036
DO - 10.1006/icar.1996.0036
M3 - Article
AN - SCOPUS:16144366742
SN - 0019-1035
VL - 120
SP - 48
EP - 65
JO - Icarus
JF - Icarus
IS - 1
ER -