Application of center-to-limb constraints from rotationally-averaged 2015-2020 HST/WFC3 imagery to constrain variations in vertical structure and chromophore properties on Jupiter

Jupiter’s ever-evolving visible clouds are composed of mainly colorless constituents, tinted with one or more coloring agents, organized into dark bands, light zones, and variously colored elliptical and elongated features, great and small. Using the temporal and wavelength coverage of bandpass imagery from HST’s WFC3 camera, we are characterizing the vertical structure and composition of various latitudinal bands and major features. Beginning in 2015, the WFC3 Outer Planet Atmospheres Legacy (OPAL) program (Simon et al. 2015, Astrophys. J. 812, 55) has provided yearly datasets with similar temporal sampling and filter sets, with which we are testing various materials’ ability to produce the colors observed on Jupiter, and characterizing the changes (cloud layers’ pressures, optical depths, and chromophore abundance) that have been observed in recent years. These observations have the advantage of access to shorter wavelengths, but lack methane band observations that would provide better constraints on vertical structure. To compensate for the disadvantage we used center-to-limb constraints. For each year of observations, we make use of rotationally averaging the 12 views of Jupiter over two rotations to further homogenize latitude bands with little spatial structure, modeling 5 zenith angle locations simultaneously to better constrain vertical structure and particle size (Fry & Sromovsky 2019, AAS/DPS/EPSC annual meeting). Although Sromovsky et al. (2017, Icarus 291, 232) were able to fit VIMS visual observations at multiple locations with the Carlson et al. (2016, Icarus 274, 106) chromophore, we were able to achieve better fits of the HST WFC3 observations with adjustable chromophore properties. We will present results of these fits and comparisons of retrieved chromophore optical properties to prior candidates (including Khare et al. (1993, Icarus 103, 290),Noy et al. (1981, J. Geophys. Res. 86, 11985), Carlson et al. (2016)), as well as to empirical refractive indices of Braude et al. (2020, Icarus 338, article id. 113589), who found that a single universal chromophore was unsatisfactory in fitting all features and epochs investigated (a conclusion also of Dahl et al. (2021, Plan. Sci. J., 2:16)). We will also present results for latitude bands additional to those previously studied (SEB, EZ, NEB, NTB) where coloration/reddening has varied with time. We will also show the ability of WFC3 Juno support imagery, with additional methane band filters, to better constrain vertical structure.