From spencer@lowell.edu Wed Dec  6 18:09:57 1995
From spencer@lowell.edu Wed Dec  6 18:09:57 1995
From: spencer@lowell.edu (John R. Spencer)
Date: Wed, 6 Dec 1995 18:02:32 -0700
To: oleroemer@lowell.edu
Subject: Io Volcano News
Cc: NNHN10A@mail.prodigy.com, spencer@lowell.edu
Content-Length: 2581
X-Lines: 53
Status: RO

18 hours to Io closest approach!!

The IRTF JOI Io monitoring run is succeeding in observing Io's thermal
emission at 8.7, 12.5, and 20.6 microns about once per day, starting
on December 3rd, using the MIRAC2 camera with a polypropylene cover
over the IRTF primary to screen out direct sunlight on the primary.
We just attempted to observe the last Io eclipse before the Galileo
flyby, at 8.7 microns, but probably don't have more than an upper
limit to the in-eclipse flux due to a combination of the short duration
of the eclipse (10 min), and Io's faintness relative to Jupiter.
Due to the priority of the probe entry site atmospheric observations,
we will probably next observe Io about five hours after the flyby,
weather permitting.

The IRTF JOI Io team is John Spencer and Jay Goguen, with able
assitance from the IRTF JOI Jupiter team:  Glenn Orton, Bill
Hoffmann, Jim Friedson, Padma Yanamandra Fisher, Sarah Stewart,
and Bill Golisch.

Tomorrow's events:

Downloaded from the "Galileo - Countdown to Jupiter" Web site (http://newproducts.jpl.nasa.gov/galileo/countdown): 

Galileo's Jupiter Orbit Insertion Timeline 

ERT - Earth Received Time, or the time when the signal from the spacecraft is actually received on the Earth.  Currently, it takes approximately 52 minutes for the signal to travel to Earth from Galileo, so ERT runs 52 minutes later 
than the actual time when an event "happens" on the spacecraft. 

Date       Time (UTC ERT) Event

Dec  7 '95   14:01        Closest approach to Europa
Dec  7 '95   18:37:41     Closest approach to Io
Dec  7 '95   22:45:27     Closest approach to Jupiter (perijove)
Dec  7 '95   22:59:24     Probe transmissions begin (60-75 minutes)
Dec  8 '95   00:14:25     Probe transmissions end   
Dec  8 '95   01:19:25     Engine firing; Jupiter orbital insertion (49 min)
Dec  8 '95   02:08:04     Nominal engine firing ends
Dec  8 '95   11:26:17     Earth occultation begins
Dec  8 '95   12:16:06     Sun occultation begins
Dec  8 '95   15:01:55     Earth occultation ends
Dec  8 '95   15:48:11     Sun occultation ends
Dec 10 thru 13 '95        First 39 min of probe data read from memory to Earth
Dec 10 '95                Communications degradation expected to begin
Dec 19 '95                Superior conjunction
Dec 28 '95                Communications degradation expected to end
Jan  3 - Mar. 13 '96      Playback of all Probe data
Mar 18 '96                Apojove maneuver
July '96                  Io Torus data playback

Here's wishing the very best of luck to our mechanical 
alter ego out there...

John Spencer.