Bolometric Bond Albedos For Saturnian Satellites From Cassini VIMS: Leading and Trailing Hemispheres

€ ≡α). The most robust photometric properties for the Saturnian icy satellites to date can therefore be determined through use of the Cassini VIMS dataset with reference to Voyager and groundbased studies. We present values, derived from VIMS hyperspectral data, of four fundamental disk-integrated spectrophotometric properties (bolometric Bond albedo, solar phase curve, phase integral, and geometric albedo at 7 to 15 different wavelengths over the full VIMS range) for five mid-sized Saturnian icy satellites: Rhea, Dione, Tethys, Mimas, and Enceladus [2]. Methodology: The bolometric Bond albedo, Abolo, is extremely important for determining the energy balance on the Saturnian moons, identifying the composition of geologic units, and finding volatile deposits. However, the geometric albedos for these moons, which factor into the determination of their Abolo values, can be very difficult to ascertain unless one has reflected light measurements at extremely small solar phase angles. Fortunately, a large amount of VIMS data is now available at down to fractions of a degree in solar phase angle for several Saturnian moons and over double the solar phase angle coverage of the Voyager mission. We constructed phase curves utilizing the publicly available Cassini VIMS hyperspectral data collection covering the period 2004-2008, searching specifically for icy satellite observations with the widest possible coverage in solar phase angle on both leading and trailing hemispheres. This allows us to provide the major photometric quantities not only for each moon (e.g., Table 1) but also Abolo, geometric albedo p(λ), and phase integral q(λ) of the leading and trailing hemispheres for each moon (e.g., Figs. 1-2, Table 2). The latter information is essential because leading/trailing dichotomies have been seen in Saturnian, Jovian, and Uranian icy satellites [3-6], yet leading and trailing photometric values, especially Abolo, were previously only available for a few of the Saturnian icy satellites. Here we use the VIMS Abolo values to determine percent brightness and first-order temperature differences between the two hemispheres. Our phase curves also span a large number of representative absorption bands and continua relevant to H2O ice (see [7] for a listing of visible to near-infrared H2O ice bands). For comparison, preliminary VIMS solar phase curves using data from July 2004 to June 2005 were constructed at selected wavelengths (λ = 0.55, 2.23 μm; [8]). Our study adds the VIMS-IR bands (λ = 0.90, 1.00, 1.52, 1.80, 2.02, 2.23, 3.60 μm) for all moons. For Rhea and Dione, we also present disk-integrated photometric properties for some VIMSVIS bands (λ = 0.35, 0.40, 0.51, 0.60, 0.70, 0.81, 0.90, 1.00 μm) and new rotational light curves at 7 nearinfrared bands not previously available in groundbased or spacecraft studies [2]. We discuss our VIMS Abolo, p(λ), q(λ), and solar phase curves in context with past ground-based and Voyager studies (e.g., [5, 9-17]), past VIMS spectral and phase curve studies [8, 18], and recent Abolo results from the Cassini CIRS team [19]. Table 1: Cassini VIMS bolometric Bond albedos Satellite Abolo Teff (K) Rhea 0.48