Voyager photometry of Io

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5338861

Simonelli, D P

Detailed disk-integrated and disk-resolved photometric studies of the Jovian moon Io were carried out using Voyager images. Disk-integrated properties derived from the Voyager data, such as phase curves, rotation curves, geometric albedos, phase integrals, and the Bond albedo, are generally consistent with earth-based estimates. Near-opposition limb-darkening behavior, as parameterized by the Minnaert photometric function, has been accurately measured for regions on the surface of Io in three distinct color classes: Bright (white), Average (orange), and Polar (brown). The limb-darkening results allow derivation of accurate near-opposition disk-resolved phase curves, revealing substantial differences in opposition surge among the color classes. Modeling of the phase curves using the Hapke photometric function supports the contention that the uppermost layer of the Ionian surface is on average extremely porous, and suggests that this layer is substantially more porous in Average and Polar areas than in the Bright regions, a difference consistent with models of Io's surface layer. Combination of limb-darkening and phase information leads to determination of accurate normal reflectance spectra for the color classes; careful comparison with laboratory data supports earlier claims that the spectra of Ionian materials can be explained by mixtures of sulfur and SO/sub 2/ frost, although this is not a unique diagnostic identification.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 5338861
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COLOR
JUPITER PLANET
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHOTOMETRY
PHYSICAL PROPERTIES
PLANETS
SATELLITES
SPACE VEHICLES
VEHICLES
VOYAGER SPACE PROBES