Io: Charting thermal emission variability with the Galileo NIMS Io Thermal Emission Database (NITED): Loki Patera

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Abstract

[1] We have calculated the ≈5-μm radiant flux for every volcanic hot spot in every one of the 190 GalileoNear-Infrared Mapping Spectrometer (NIMS) tube observations of Io obtained between 28 June 1996 and 16 October 2001 in order to determine the variability of thermal emission from Io's volcanoes at local, regional and global scales, and to identify individual eruption episodes where thermal emission waxes and wanes. The resulting NIMS Io Thermal Emission Database (NITED) allows the comparison of activity at individual volcanoes and different regions of Io. The database contains over 1000 measurements of radiant flux at approximately 5μm, corrected for emission angle, range to target and incident sunlight (where necessary). We examine the data for Loki Patera, Io's most powerful volcano. For data acquired in local darkness we use two-temperature fits to nighttime spectra and prior knowledge of emitting area to determine total radiated thermal emission. For other data we use the constancy of the integrated thermal emission spectrum to determine total thermal emission from measurements of radiant flux at 5μm. As seen by NIMS, total thermal emission from Loki Patera varies between 7600 GW and 17000 GW. We revise upwards previous estimates of thermal emission from NIMS data. NIMS 3.5-μm radiant fluxes (both measured and estimated) are consistent with measurements from ground-based telescopes. This work highlights the value of NITED as a research tool.

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