Studying the icy moons of Jupiter using a database framework

The NASA Galileo spacecraft explored the Jupiter system between 1995 and 2003. The spacecraft was equipped with the Near-Infrared Mapping Spectrometer instrument (NIMS), able to probe Jupiter’s atmosphere and the icy moons’ surface composition in the near-infrared with its 17 detectors operating between 0.7 to 5.2 microns [1]. The Galileo NIMS dataset was collected during flybys, which resulted in a series of very diverse data cubes, viewing geometries and spatial resolutions. In addition, depending on the instrument mode used to collect the data, and on the instrument’s own health status, the NIMS infrared spectra were collected with a varying spectral sampling (between 15 and 408 wavelengths), and an evolving absolute wavelength calibration over the course of the mission. Despite its heterogeneity and complexity of use, the Galileo/NIMS dataset is one of the most valuable resource to model and map the surface properties (composition, grain size, roughness, phase function) of Jupiter’s moons, which are the prime targets of the Europa Clipper [2] and ESA JUICE [3] missions in this decade. We converted the Galileo/NIMS calibrated dataset publicly available on the PDS Imaging Node (as g-cubes) into a MySQL relational database, which allows to quickly select and extract radiance factors (I/F), geometry data, and metadata from the entire NIMS data set. The smallest element in the database is a spectrum (i.e. one pixel). Using SQL queries relying on the pixel viewing geometry (incidence, emission, phase, and azimuth) and the geographic pixel location (latitudes and longitudes on a target), phase curves and/or collections of spectra can be easily retrieved. Individual g-cubes data can also be accessed upon request. We used this database framework, together with Bayesian inversion methods and the Hapke model [4,5], to perform detailed compositional studies on Europa’s dark lineaments [6,7], and spectro-photometric modeling of broader regions of interest located in different hemispheres [8].   References [1] Carlson et al., Space Science Reviews, 60, 457-502, 1992. [2] Howell and Pappalardo, Nat Commun 11, 1311, 2020. [3] Grasset et al., Plan Spac Sci 78, 1-21, 2013. [4] Hapke, Icarus 221, 1079-1083, 2012. [5] Hapke, Cambridge University Press, 1993. [6] Cruz Mermy et al., Icarus 394, 115379, 2023. [7] Andrieu et al., EPSC 2022. [8] Belgacem et al., EPSC, 2022.