From spencer@lowell.edu Wed Jul 26 23:42:31 1995
From spencer@lowell.edu Wed Jul 26 23:42:31 1995
From: spencer@lowell.edu (John R. Spencer)
Date: Wed, 26 Jul 95 23:39:26 MST
To: oleroemer@lowell.edu
Subject: Io Volcano News
Cc: hicksm@lowell.edu, spencer@lowell.edu
Content-Length: 1557
X-Lines: 33
Status: RO


I just observed the 7/27 occultation and eclipse of Io by
Jupiter from the IRTF in marginal conditions, and Michael
Hicks observed it in much better conditions at the Lowell
72".  Michael reported that Io was still unusually bright
at 2.3 microns in eclipse, indicating that the eruption first
seen on 7/25 is continuing.

Analysis of the 7/25 Jupiter occultation egress lightcurve
that we got at the IRTF shows that about half the 3.5 micron
volcanic flux was coming from the "new" hot spot, and that
the spot is *not* at Surt as I had originally suspected,
but is instead further west: the constraint does not pass
very close to any known hot spot.  The occultation egress
of Loki, contributing about 1/4 of the total flux, and another
spot to the east (maybe Kanehekili), contributing most of the
remainder, were also clearly visible.

Jay Goguen reports on the observations by the JPL group
at longer wavelengths on 7/18- apparently the new eruption
had not started then...

We had a radiometry run at IRTF a week ago (7/18 UT) and the in-eclipse 
M mag of Io was 5.6 - that should be good for a comparison.  We judged
from the M, 8.7, 12.5 and Q mags that there wasn't much going on at that
time that was unusual, so this new brightening should be pretty well 
constrained in time.  We have time at Palomar 8/4-5 and 7-11 (short stints
each night with MOP and MIRLIN) and half-nights on IRTF 8/16-23 so there 
should be good opportunities to watch this eruption evolve at all wavelengths
if it lasts a little while.

That's all for now,
John Spencer.