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D. L. Matson, J. D. Goguen, D. L. Blaney, G. J. Veeder, T. V. Johnson (JPL/Caltech)
We report recent results from our program of mid-IR global radiometry of Io carried out mainly with the NASA IRTF. Although the disk-integrated radiometry lacks the spectacular spatial resolution afforded by imaging at near-IR wavelengths when Io is in eclipse (e.g. see HST NICMOS image reported in Goguen's abstract, this meeting), there are some important ways that these observations make a unique contribution to the study of Io's volcanism:
1) Io's global heat flow is dominated by the power radiated over the 4.8-20\mum spectral range. 10\mum region radiometry is required to detect the large area of warm flows that characterize the emitted power. Io's volcanos are thought to be a source of it's atmosphere and the mass that supplies the torus, magnetospheric, and auroral phenomena. Characterizing Io's volcanic activity may prove to be a key element in understanding many of the phenomena that Galileo studies during its tour of the Jovian system.
2) Our measurements cover the region of the spectrum that fills the gap between Galileo's NIMS (1-5\mum) and PPR (\gtrsim17\mum) instruments. Although the 10\mum region is critical to understanding the energetics of Io's volcanism, it is a region of the spectrum over which the Galileo spacecraft is effectively "blind".
3) Our data provide both a both spatial and temporal context for the Galileo coverage. Galileo flies through the satellite system during a few days on each of it's 25 orbits acquiring high spatial resolution "snapshots", typically with the best resolution concentrated on Io's anti-jovian hemisphere. This program's long baseline of consistent radiometry covering all longitudes establishes both the global context into which the focussed Galileo data fit as well as provides a comparison of how Io's volcanic state during Galileo compares with historical data spanning more than a decade.
This poster will focus on mid-IR radiometric results during the period from the arrival of the Galileo spacecraft at Jupiter to date.