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               PHEMU03 Letter n°1
                  May 23, 2002
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Contents:
1) Introduction to the PHEMU 03 campaign
2) The 2002-2003 occurrence
3) Why a new campaign of observation?
4) Where to observe?
5) The available information
6) Financial support available for the observations
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1) Introduction

A new occurrence of mutual events of the Galilean 
Satellites of Jupiter is from October 2002 for and 
it is time to prepare the campaign of observations.
If you participated to the previous campaigns,
we count on you to make and to gather
valuable data. If not, we will be glad if you accept
to participate to the campaign of observations: you 
will find information on it through our web site.
Please, acknowledge receipt of the
present letter, confirm your e-mail address, and send 
us the e-mail addresses of colleagues able to participate 
to the campaign of observation. Don't forget that
these events do not require neither large telescopes
(galilean satellites have a magnitude about 5)
nor high sensitive receptors (only a fast CCD
camera or a video camera with a VCR recorder)
for observations in the visible wavelengths.
Only observations made in infrared wavelengths
need a large telescope.
Don't forget that the observation of these events,
even with a small telescope, provide valuable 
scientific data.

2) The 2002-2003 occurrence

The 2002-2003 occurrence is particularly favorable
because of the opposition of Jupiter at the time of the
most important events. The declination of Jupiter
is about +18° and this makes easy the observations
for most of the observatories. The list of the
events to be observed in priority is available
on our web site at:
http://www.bdl.fr/Phemu03/phemu03_eng.html 
We plan to provide you soon a software allowing the 
calculation of local conditions of observation for 
any site.

3) Why a new campaign of observation?

The observation of mutual events started
in 1973. At that time only a few events were observed
but are still interesting. We learned from the first
observations how to make the reduction in order
to get the astrometric and photometric information 
from the light curves. Observations were made in
1979 (very few because of the conjonction of Jupiter 
and the Sun at the time of the events), in 1985, 1991 
and 1997. Most of the light curves were reduced
and put into evidence the high astrometric accuracy
of the observed relative positions between the
satellites. This accuracy, not reachable through
classical CCD observations, allows to fit the
dynamical models of the motion of the satellites.
One of the problems not solved in the motion
of the satellites, is the measure of the loss
of energy due to the tide effect. This loss of
energy should appear and should be measured 
through the measurement of an acceleration in the motion
of the satellites, and will have numerous consequences 
in the modeling of the interior of the satellites 
themselves. This acceleration can be measured only through
observations sufficiently accurate made on a
sufficiently long interval of time. That is one
of the challenges for the galilean satellites knowledge
and that is why a new campaign of observation is
useful considering the results of the past campaigns.

4) Where to observe?

In fact, the most important goal of the campaign
is to get the observation of the largest number
of different events. This imply that observations
were made from observatories well situated on Earth: 
we must have observers at any longitude to be able
to catch all the events since these events occur at 
any time. We must be able to observe Jupiter at any 
time.
So, we should make some efforts to have observational
sites at longitudes east from Europe as it is shown
on the map available on our web site.

5) The available information

The information about the PHEMU03 campaign is 
available at the address:
http://www.bdl.fr/Phemu03/phemu03_eng.html
You will find the list of the events, several
technical notes in order to help the observers,
some proceedings of workshops on the mutual
events and some softwares useful to prepare
or to reduce and analyze the observations of
the mutual phenomena.

6) Financial support available for the observations

In order to prepare the campaign of observations, we
apply for grants from several organisms and we obtained
some results. We are able to provide a financial support
for observers encountering difficulties for their
travels to the observing site or for the acquisition
of small material useful for the recording of the data.
We encourage you to ask for a financial support near
your organism but you may send us a demand of support
for the campaign using the application form
available on our web site at the address:
http://www.bdl.fr/Phemu03/applicationform03.html
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Dr Jean-Eudes ARLOT
Institut de mecanique celeste
Observatoire de Paris/Bureau des longitudes
UMR 8028 du CNRS
77 avenue Denfert-Rochereau
F-75014 Paris
tel.: (33) 1 40 51 22 67
fax: (33) 1 46 33 28 34
e-mail: arlot@bdl.fr
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