Photometric Properties of Vesta

Abstract

The Dawn spacecraft orbited Asteroid (4) Vesta for a year, and returned diskresolved images and spectra covering visible and near-infrared wavelengths at scales as high as 20 m/pix. The visible geometric albedo of Vesta is ∼ 0.36. The disk-integrated phase function of Vesta in the visible wavelengths derived from Dawn approach data, previous ground-based observations, and Rosetta OSIRIS observations is consistent with an IAU H-G phase law with H=3.2 mag and G=0.28. Hapke's modeling yields a disk-averaged single-scattering albedo of 0.50, an asymmetry factor of -0.25, and a roughness parameter of ∼20 deg at 700 nm wavelength. Vesta's surface displays the largest albedo variations observed so far on asteroids, ranging from ∼0.10 to ∼0.76 in geometric albedo in the visible wavelengths. The phase function of Vesta displays obvious systematic variations with respect to wavelength, with steeper slopes within the 1-and 2-micron pyroxene bands, consistent with previous ground-based observations and laboratory measurement of HED meteorites showing deeper bands at higher phase angles. The relatively high albedo of Vesta suggests significant contribution of multiple scattering. The non-linear effect of multiple scattering and the possible systematic variations of phase function with albedo across the surface of Vesta may invalidate the traditional algorithm of applying photometric correction on airless planetary surfaces.179

A deep crust–mantle boundary in the asteroid 4 Vesta

“…Then pixels where observation angles are too high (.75u) are removed using photrim. Finally, we apply a photometric correction with the photomet function (in HapkeHen mode) and using the parameters found in the literature [32][33][34] (macroscopic roughness parameter h 5 20, single-scattering albedo Wh 5 0.52, single-term Henyey-Greenstein coefficient Hg1 5 20.29, width of the opposition surge Hh 5 0.04, amplitude of the opposition surge B0 5 1.03).…”

Lithologic mapping of HED terrains on Vesta using Dawn Framing Camera color data

“…The data are photometrically corrected using Hapke functions derived from disk‐integrated, ground‐based telescopic and Dawn spacecraft observations of Vesta and vestoids (Li et al. ). The data are map‐projected and coregistered to align the seven color frames to create the color cubes.…”

“…Therefore, band depth is not uniquely affected by composition, but also by particle size. The band depth on Vesta is also affected by phase angle, temperature, iron abundance, and the presence of opaques (Hiroi et al 1994;Duffard et al 2005;Reddy et al 2012).…”

“…Band Strength (BS) and Albedo at 0.749 lm Despite variations in albedo at 0.75 lm and band depth of HEDs, a correlation between band depth and albedo exists (Reddy et al 2012). The scatter plot of BS and albedo for the HEDs, irrespective of the particle size ( Fig.…”

Joint Anomaly Detection and Spectral Unmixing for Planetary Hyperspectral Images

“…Raw images were downloaded from PDS in level 1B and were calibrated using ISIS3 pipeline [60] and photometric parameters found in the literature [61]- [63]. Additional inhouse routines were used to filter bad pixels and to correct the geographical misalignment between the two detectors of the VIR instrument (following the method described in [54]).…”