From spencer@lowell.edu Tue Sep  5 15:11:51 1995
From spencer@lowell.edu Tue Sep  5 15:11:51 1995
From: spencer@lowell.edu (John R. Spencer)
Date: Tue, 5 Sep 1995 12:42:22 -0700
To: oleroemer@lowell.edu
Subject: Io Volcano News
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Status: RO

Jane Spencer and I observed another Io eclipse and occultation
by Jupiter on September 4th, using the OSIRIS camera at the
Perkins 72" telescope at Lowell. 

The occultation lightcurve was at 2.3 microns, so can be directly
compared to the August 19th lightcurve at the same wavelength:

                             Flux ratio,               Position
              Fraction 2.3    Sept. 4 /   August 26   Uncertainty,  First
Hot Spot       micron flux    August 19   Lat.  Lon.  +/- degrees   seen
-----------------------------------------------------------------------------
Loki              0.33         1.9       15 N   310 W    5         1979/03/05
"Late July"       0.38         0.5       22 N   351 W    5         1995/07/20
"Mid August"+     0.15         0.3       28 N    12 W    8         1995/08/19
"Faint South"                            35 S     0 W  >10
"Kanehekili"      0.10         0.8       10 S    40 W   10         1989/12/24
"Hi`iaka"       c.0.03         1.0?       0 N    70 W   20         1990/03/21

Comparison of the September 4th and August 26th lightcurves suggests
that Loki did most of its brightening before August 26th, and the "Mid
August" spot did most of its fading after August 26th, while the "Late
July" spot may have brightened up again since August 26th.  However,
because the August 26th IRTF lightcurve was at 3.5 microns, comparison
with the 2.3 micron September 4th lightcurve depends on the dubious 
assumption that all spots have simliar temperatures.

Note also that in Lowell observations the "Mid August" and "Faint South"
spots can't be distinguished, as both emerge from Jupiter occultation 
simultaneously.  Disk-resolved IRTF observations are required to separate
them.

Automated "daily monitoring" of Io at the IRTF began on September 3rd UT,
under the guidance of Glenn Orton: images of Io's anti-Jupiter hemisphere
on that day were blurry due to poor seeing but showed nothing unusual.