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From fmarchis@astron.Berkeley.EDU Wed Dec 27 21:44:01 2000
To: oleroemer@torridon.lowell.edu
CC: fmarchis@astron.Berkeley.EDU
Subject: AO Observations of Io with ADONIS system - very bright polar emission
See web page at http://astron.berkeley.edu/~fmarchis/Io_OA/Run2000/
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Monitoring of Io in coordination with the Galileo/GEM - Cassini campaign by
ADONIS Adaptive Optics.
Franck Marchis, Renée Prangé and Thierry Fusco
Our observations taken the 16th of December 2000 show the presence of a active hot spot (0012A) on the northern polar region of Io.
Observations have been performed using the ADONIS Adaptive Optics and its infrared-thermal camera COMIC (L' band, 3.8 micron) . We applied a blind deconvolution method (MISTRAL) and a basic solar reflection model to better isolate the hot spot emission (see Marchis et al., ICARUS, 148, 384-396, 2000). A major emission is located at (130+/-15 , 63+/-10) with a brightening of 115 +/- 5 GW/micron/sr (after applying a classical cos \Theta law). Even if its location is uncertain due to its position at the edge of the disc (see figure), it may correspond to the location of the Tvashtar (9911A event) already observed last year. It is one of the most active hot spot detected since the beginning of our survey (4 years ago). For instance, in November 1999, at its maximum of activity, Loki reached a similar brightness (see Howell et al., submitted to JGR, 2000).
The Solar/total ratio flux is around 86%. Additional hot spots contribute to this thermal emission, mainly several area corresponding to Volund-Zamama, Pillan,and the ring of fire hot spots (Amirani-Maui-Monan, Hi'iaka-Sigurd, Malik-Altjirra). Additional observations taken in November 2000 will be soon processed.
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Cheers Franck M.
