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IAU Colloquium 156 : The Collision of Comet P/Shoemaker-Levy 9 and Jupiter
IAU Colloquium 156 Workshop Information

	Workshop Information for IAU Colloquium 156

Here is information on the various workshops that will be held 
each afternoon. If you wish to participate in any of these
workshops, please contact the relevant convenor(s) expressing
your interest.


TUESDAY 9 MAY 1995 2:00 PM - 6:00 PM
Title: Flash Reflections (limits, etc.)
Convenor: Mike A'Hearn (
There is still dispute about whether Galileo's SSI and PPR 
observed the impacting bolide, the rising fireball, or some
combination of the two (NIMS clearly observed a rising
fireball).  Earth-based optical observations of flashes
in reflection from the satellites are very puzzling. The
most realistic looking flashes imply luminous energies 
considerably in excess of those observed by Galileo 
(albeit at different wavelengths) and none of these 
most realistic looking ones have been confirmed from
multiple sites. Other flashes, looking more like noise,
have been confirmed at multiple sites to within about 
one or two seconds.  Some flashes appear to occur at times
that slightly precede the precursor events observed in the
near infrared. This workshop will attempt to extract all
possible observations from different sites and correlate
their times both with the times of optical flashes observed
at other sites and with observations in the infrared.


	Open letter from Mike A'Hearn to Workshop Participants

Dear Colleagues,

    Like many other workshop organizers for IAU Colloquium 156, I am making
a plea for data relevant to the workshop I am organizing.  I will be running
the workshop on impact flashes seen either at the limb or in reflection
from the satellites.  I presume that the emphasis will be on the optical
flashes but the timing of optical flashes relative to the precursor flashes
seen in the near infrared is also very important so I hope that we will have
participation by the infrared observers also.  I would particularly welcome 
participation also by experienced meteor astronomers who could comment on 
the colors of the flash expected from a bolide in Jupiter's atmosphere.

     I would like to start the workshop with a preliminary table of all the 
possible detections of flashes.  Many people have already published in one
way or another the times of possible flashes but others have not.  The key
things I hope to accomplish at the workshop include establishing the accuracy
of the times, identifying all possible coincidences from more than one site,
and directly comparing actual photometric records for shape and size of the
flash.  We will then try to assess which of the detections might be real.

     After considering the photometric records of flashes, we will consider
the spectroscopic detections.  The instrumental problems are entirely
different and the interpretation may also be different.

     I would appreciate hearing from anyone who might have data relevant to
the impact flashes, particularly from people whose observations have not 
already been announced.  A list of times of possible event sin your data is
the most urgent item.  Meanwhile, to aid in searches of other datasets, I
will provide in a week or two a complete list of the times available to me
at that time.  This list will be posted on the SL9 electronic bulletin

					Mike A'Hearn
					University of Maryland

PS:  Note that this message is not being sent from my normal email address
so please do not use the reply command as it will only delay my receipt of
your message.


Title: Synthesize Phenomena (G & W)
Convenor: Alan Fitzsimmons (af@
The primary aim of this workshop will be to examine
the available observations (and interpretations where
held!) of the impacts of the G&W fragments. During the
workshop we should address two primary goals:

(a) The creation of a complete as possible chronology for
both impacts, from first detection to subsequent evolution
of the plume debris on Jupiter. Given this, it is important
that the most crucial datasets (high-resolution imaging,
multi-wavelength spectroscopy) be discussed. In particular,
are there observables associated with these impacts that
may not have been seen with other events?

(b) To inter-compare data from both ground and space-based
observatories. For example, How does the visual luminosity
as seen by Galileo compare with the IR precursors observed from
the ground? Can we produce a multi-wavelength spectrum for the
plumes at any given instant? How does the grain size in the plume
compare with the corresponding particulates in the impact site
hours/days/weeks afterwards?

Title: Synthesis of Impact Times
Convenor: Don Yeomans (
The goal of this workshop will be to examine the impact
time predictions in light of the relevant observations
from ground-based observatories, the Hubble Space
Telescope, and the Galileo spacecraft and to determine,
to the extent possible, the actual impact times and
their associated uncertainties.


WEDNESDAY 10 MAY 1995 2:00 PM - 6:00 PM

Title: Synthesize Phenomena (K, L & R)
Convenor: Richard West (

1) Establish for each impact an overview of what material was really
obtained (instrument characteristics, observation epoch, "quality"),
so that all groups know which material may complement theirs

2) Divide this material in to a logical (chronological) sequence of
the main "phases", e.g. Flashes - Plumes - Splashes - Early direct
views - Long-term evolution.

3) Within each of these phases, animate a "joint discussion", i.e. by
combining all what is available from the individual impacts (in my
case, K, L and R) to find out whether there are:

  a) full agreement among the groups about what was observed
  b) obvious disagreements, which should then be exposed and possibly
     elucidated, whereby a list of "open questions" may be prepared
  c) any particular, "unique" observed events, which indicate 
     qualitative differences between the individual impact sequences

4) To invite the model builders to comment on the various points that
come up during each of the "phases", immediately following the
discussion among the observers. In particular:

  a) does the information from the observations as presented make it
     possible to draw some (new) conclusions about the process(es)?
  b) can we now put some numbers on the models, or, which of these
     observations may be particularly crucial for the models? For 
     instance, which "combinations" of observations are especially
     useful and should be pursued?

5) At the end, to "synthesize" the outcome of these discussions on the
spot, i.e. to mention the main points which came up and suggest
specific lines of action.

***If you want to participate in this particular workshop,
***it would be helpful if you would fill out the following
***questionaire and return it to Richard West.


QUESTIONAIRE (please fill in and return to before May 5))


Thank you for taking a few minutes to fill this in !

Name                       :
Observatory                :

Which event (K, L or R)    :

Type of obs.(direct/spectr): 
Telescope                  :
Instrument                 :
Wavelength interval        :
Approx. ang. resolution(") :
Approx. spectr. resolution :

Observing interval (UT)    :
No. of frames/spectra      :
Observing conditions       :

Provisional results (brief):
e.g. timings, emitters

Related papers published   :


Title: Comparison of Impact Models
Convenor: Glenn Orton (
This workshop will overview various approaches to the impact modeling in light
of available observational results.  In general, what are the points on which
the models are in significant agreement?  For example, is there a consensus on
the interpretation of the most sensitive 3-peaked impact lightcurves? Among the
disagreements between models, which originate with the numerical approach and
which with basic assumptions about the important processes?  What hope is there
for reconciling or discriminating among the approaches based on the
observations?  Are there physical observations which are not well described by
the models?  What has been most significantly changed about our concepts of the
important processes in impacts by the observations of this event?

Title: What about the Weak/Missing Impacts?
Convenor: Hal Weaver (
During our studies of SL9-Jupiter impact phenomena, we have
focussed our attention primarily on the most spectacular 
events. However, perhaps much can be learned by assessing
what happened during the smaller impacts. Since the
magnitude of the impact phenomena varied from being
visually spectacular to undetectable, nature has provided
a range of input parameters over which model predictions
can be tested. Some of the questions addressed in this
workshop include:

	1) How do we rank the impacts?
	2) What was the most sensitive technique for
	detecting post-impact phenomena?
	3) Do observations of the fragments prior to impact
	provide clues as to what impact phenomena were
	4) Can variations in impact phenomena be explained
	solely by fragment size variations, or are structural
	variations in the fragments also required?
	5) Exactly what happened to the SL9 fragments that
In order to address these issues we need to synthesize data 
from both the pre-impact observations of the comet and the 
post-impact observations of Jupiter.


THURSDAY 11 MAY 1995 2:00 PM - 6:00 PM

Title: Magnetospheric Effects
Convenor: Renee Prange (
Signatures of the interaction of comet SL9 with the Jovian 
magnetosphere have been recorded in a variety of wavelengths
from X rays to radioemission. They have been obtained at 
different times, including after the impact period. This worshop
will first allow to organize the set of specific observations
available (i.e. nature, date, coordinates, characteristics) in
order to identify related events and any relationship with the
comet fragment histories. 
Theoretical models have been developed, both before the collision,
and after the effects were observed. Their ability to interpret the
various sets of related events as a whole will be dicussed, as well as
the need for any further theoretical effort.
Anticipated topics might be grouped into 
- global activity
- localized interaction of the coma with the high latitude magnetosphere
- torus effects
- electrodynamic effects on the impact field lines (including synchrotron radiation)  

Title: Pre-1992 History	of SL9
Convenor: Paul Chodas (
Following the motion of comet Shoemaker-Levy 9 backwards in time can
provide clues to the nature and origin of the object.  An accurate pre-
breakup ephemeris is essential in searching for possible detections of
the parent object in existing images of the Jupiter region.  If we could
be sure of the ephemeris, even a non-detection would be useful in putting
limits on the progenitor nucleus size.  Backwards integrations can also
shed light on the capture mechanism and provide insight into where the
object came from.  Questions addressed in this workshop include:

        * How do the results of various backward integrations compare?
        * What are the uncertainties in pre-breakup ephemerides?
        * What searches have been conducted for pre-breakup detections?
        * When was SL9 captured by Jupiter and from what kind of helio-
          centric orbit?
        * Is it important to model the perturbations due to Jupiter's
          oblateness and the Galilean satellites?
        * Are we omitting any important perturbations?
        * How do we solve the Humpty-Dumpty problem, ie, how do we
          determine the orbit of the progenitor nucleus from the orbits
          of the fragments?

Title: Multiwavelength Atomic and Molecular Abundance 
	Determinations: Reconciling Differences
Convenor: Keith Noll (
Determination of the chemical composition of Jupiter's atmosphere in 
regions perturbed by the impact of SL9 is a key observable that can be 
used to constrain models of impact-induced chemistry and possibly the 
composition/size/depth of the impactors.  Several of the most 
abundant molecules were observed in more than one transition at 
wavelengths from the UV to the mm.  In some cases, the abundances 
derived from such observations differ by orders of magnitude.  The 
purpose of this workshop will be to explore the details of independent 
abundance determinations for gases such as CO, NH3, and C2H2 in an 
attempt to characterize possible causes for divergent results.  
Possible avenues to explore are rapid variation of molecular abundance 
with altitude, assumptions about model inputs such as temperature, 
differences in beam size and sample area, temporal variability, and 
issues of data quality.


FRIDAY 12 MAY 1995 2:00 PM - 4:00 PM

Title: Conference Summary
Convenor: Gene Shoemaker
This is a plenary session in which Gene Shoemaker will attempt
to summarize the highlights from the meeting.