(updated 2012-Nov-04)

JEE2012 Observing Campaign, Io Torus Tip Transits


Predictions of Io Torus Tip Jovian Extinction Events (ITTJEE) in PDF format:

(NOTE: If you downloaded predictions prior to November 4, 2012 you will need to download the new and improved Version 2)


(Click here to see prediction format description)










Io Torus Tip Extinction Events Summary:


Torus Tips labelled.png


Torus JEE schematic.png



During the IAEP2009 and JEE2010 Observing Campaigns it was established that Io suffers a sort of “self-extinction” while it transits its own orbit at the tips inside the Torus of Io. There is enough stray gas and particles to cause detectable magnitude loss with standard unfiltered observing equipment via extinction of the reflected sunlight from Io as it is diminished by the collimated line of sight Torus material at the most extreme eastern and western tips of the Torus. In 2010 John Talbot of New Zealand captured 5 hours of video during most of an Io transit of its western Torus tip. At that time in November of 2010 the orbit of Io was only 0.4 degrees inclined to our view from earth. This presented a large amount of Torus material collimated to our view which caused a very notable extinction event during the transit. The data from that run enabled us to derive a 5th order polynomial fit to Western Torus Tip transits of Io and has enabled us to create reliable predictions of future Io Torus JEE.






For JEE2012 the alignment of the Torus material is not as favorable, as Io’s orbit is about 3 degrees inclined. But early data from JEE2012 in July and August has shown that the extinction is still detectable at this less favorable of an angle:





Given that early JEE2012 encouraging data showing Torus Tip events as still detectable with our standard equipment we will be providing predictions for all Torus Tip JEEs. Observing these is as easy as it gets. Point your telescope to Jupiter during the window of time and hit record on your video system. Make sure you keep Io in the field of view and at least one other moon, preferably Ganymede or Europa in the field of view as well. Make sure you do not over expose the moons so that they are in saturation, but also do not underexpose the either. Jupiter will be over exposed to get the moons at the right intensity for your recording. Video is not necessary to record these, but it is certainly the least amount of work for both data capture and reduction.


At the moment we do not have enough data to have the same accurate fit for Eastern Torus Tip JEE. We hope to accomplish that with JEE2012 data.


Spectroscopic observations are encouraged for these Torus Tip transits in order to get the ingredients of the “soup” that surrounds Io.


Check back for all future events to be posted soon. Any questions or data to submit please address them to:


Scott Degenhardt  scotty@scottysmightymini.com


Prediction format:


·         UT Date and time of when Io is at elongation (furthest from Jupiter, thus in the center of its Torus Tip)

·         The “Tip” column will tell you which side of Jupiter Io is on

·         The times of the expected start and stop of extinction and the minima is given

·         All predictions are estimates and are likely accurate to within 5 minutes UT

·         Image Io as long as possible during these torus Tip transits, and be sure to include data outside of these predicted times (a minimum of 30 minutes or more when possible) to provide a baseline

·         Keep at least one other moon of Jupiter in your field of view to use as a photometric reference, preferably Europa or Ganymede

·         As with all photometry do not overexpose nor under expose your images

·         Video imaging seems to be the easiest way to document such lengthy photometric runs


Sample predictions:

Date Time UT






 2012-Nov-28 23:31






Date Time UT






 2012-Nov-29 20:44








Jovian Extinction Event Torus Tip Predictions:


Scott Degenhardt  September 8, 2012

Send data correspondence to scotty@scottysmightymini.com


Predictions package:  http://scottysmightymini.com/JEE/JEE2012Sep_TorusTipPredictions.pdf

JEE Results: http://scottysmightymini.com/JEE/results/


Ephemeris Source:




Solar System Dynamics Group, Horizons On-Line Ephemeris System

     4800 Oak Grove Drive, Jet Propulsion Laboratory

     Pasadena, CA  91109   USA

     Information: http://ssd.jpl.nasa.gov/

     Connect    : telnet://ssd.jpl.nasa.gov:6775  (via browser)

                  telnet ssd.jpl.nasa.gov 6775    (via command-line)

     Author     : Jon.Giorgini@jpl.nasa.gov


Stellar JEE occultation predictions using Occult 4, Herald, D. et. al

Other Modeling tools:


     Microsoft Excel macro developed by Scott Degenhardt


The IAEP team and data from that study:


Scott Degenhardt, S. Aguirre, M. Hoskinson, A. Scheck, B. Timerson

International Occultation Timing Association (IOTA)


D. Clark

Administaff/Humble ISD Observatory


T. Redding

IOTA, Redding Observatory South


J. Talbot

RASNZ Occultation Section


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