Report from the Vilnius workshop
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GAIA-CUO-090     E. Hoeg        17 July 2001

ABSTRACT:
Information about the workshop is given in
http://www.astro.ku.dk/~erik/gaia/90.Vilnius.workshop:
- GAIA Photometry tasks
- corrected figure of the sampling
- Perryman's summary for the discussion in Vilnius
- Report from the Vilnius workshop CUO-90, by Hoeg.

The workshop was held on 3-5 July with 22 oral presentations, 15
posters, and a general discussion. There were 38 participants, 22 of 
them came from 11 other countries than Lithuania,
see details of program etc. on http://www.astro.lt/gaia.
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The workshop was the first full-scale meeting of the Photometry Working
Group. Even though some core members, eg. Brown and Munari, were missing
the strength and devotion of the PWG stood out clearly. 

Perryman writes very truly in a message of July 6 to the organisers:

  I would like to thank you again for a very interesting and 
  successful meeting, and for all the effort which went into 
  preparing it. It was very obvious that much work and care went 
  into the planning and execution - note only of the scientific
  programme - but also the local organisation. The tour and 
  the two evening dinners were also excellent; one does not always
  expect such standards at these meetings, but of course these
  aspects do add greatly to the enjoyment and the memories that
  the participants take away. The duration was also well chosen - 
  enough for people to get to know each other, and their working
  practices. The meeting has raised many questions and actions for 
  the photometry group; but also many avenues to be followed which 
  should eventually lead to their success. For me personally, it
  was a wonderful opportunity to make first contact with your
  country.

  Congratulations again, and our thanks to all involved.

  regards
  
  Michael
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The issues appear from Perryman's summary for the general 
discussion (see separate file).

It was agreed that it is possible to arrive at a common photometric system
(PS) within a year based on current spectra, observed or synthetic.
Further improvements of this system may be possible up to June 2005
(TBC), depending on the satellite system implications, and depending 
on the impact that such changes are likely to have on the photometric 
studies carried out previously.

A schedule is given in "GAIA Photometry tasks", see separate file.
The PS should be based on *single* stars across the HR diagram.
The performance should then be assessed on other objects:
binaries, asteroids, planets, galaxies, quasars etc.

The question was much discussed whether the PS must 
be tested from the ground, or current spectra are sufficient. 
Two applications to fund such filters and the test observations
have already failed. All efforts must be excerted to define and
collect missing spectra, and to base the PS hereon. 

Ground-based use of the resulting PS in filter observations is still 
desirable for a number of reasons, given in Perrymans's summary. 
It is encouraged to do science with the filters before the launch 
of GAIA, this would thus have a time-scale of a decade. 

Further improvement of the PS up to 2005 may be based on studies of
spectra, observations with filters, and on the assessment on other
objects than single stars. 

Ground-based observations with filters for the test of the PS should 
be based on a thorough discussion of the possible gain, a realistic 
schedule and a realistic proposal for implementation on the ground. 
A technical document with this discussion can be considered by all 
colleagues who have an interest in making the GAIA photometry 
successful, and final conclusions can be drawn.
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