Galileo photometry of asteroid 243 Ida

P. Helfenstein, J. Veverka, P. C. Thomas, D. P. Simonelli, K. Klaasen, T. V. Johnson, F. Fanale, J. Granahan, A. S. McEwen, M. Belton, C. Chapman

Research output: Contribution to journalArticle

99 Scopus citations

Abstract

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).

Original languageEnglish (US)
Pages (from-to)48-65
Number of pages18
JournalIcarus
Volume120
Issue number1
DOIs
StatePublished - Mar 1996
Externally publishedYes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Helfenstein, P., Veverka, J., Thomas, P. C., Simonelli, D. P., Klaasen, K., Johnson, T. V., Fanale, F., Granahan, J., McEwen, A. S., Belton, M., & Chapman, C. (1996). Galileo photometry of asteroid 243 Ida. Icarus, 120(1), 48-65. https://doi.org/10.1006/icar.1996.0036