From spencer Fri Jan 7 16:06:56 1994 From spencer Fri Jan 7 16:06:56 1994 Return-Path: Date: Fri, 7 Jan 94 16:06:55 MST From: spencer (John R. Spencer) To: spencer@sunkng Subject: Io Volcano News Content-Length: 1583 X-Lines: 33 Status: RO IO VOLCANO NEWS January 7, 1994 I'm happy to open the 1994 Io observing season with news of enhanced volcanic activity at Loki, which had been relatively quiet in all observations since the winter 1991 brightening. We observed Io with the new NSFCAM InSb camera at the IRTF on January 6th UT, in "service" mode with John Rayner and Lars Bergknut at the telescope and myself and Michael Person at Lowell Observatory, participating over the Internet. A bright hot spot was seen against Io's sunlit disk at 4.8 and 3.8 microns with 1/2 arcsecond seeing: the first time a spot has been visible in sunlight at 3.8 microns since winter 1991. Visually, its location appeared to be consistent with Loki. In Jupiter eclipse, a single hot spot dominated the emission from Io, with total flux similar to that during the winter 1991 Loki brightening, and several times brighter than in the Fall 1991 - Summer 1993 period. No other hot spots were immediately visible despite the good seeing. The exact location of the bright hot spot will require further analysis of the sunlit images and the Jupiter occultation lightcurve, but I am fairly confident that it is Loki. Previous Loki brightenings have lasted a few months, but unfortunately no more IRTF observations will be possible till April, when the telescope upgrade is completed. I'd like to compile a list of planned observations of Io or the other Galilean satellites during 1994, for general distribution. Please let me know what your observing plans are. Best wishes, John.