Report on Gaia Symposium
13 October 2004Between 4-7 October, a major symposium dedicated to the scientificaspects of the Gaia mission was held at the Observatoire de Paris,Meudon, France, as 'Les Rencontres de l'Observatoire 2004'. Attendedby 240 delegates, the four-day meeting was an opportunity to presentthe current status of the Gaia mission to the interested scientificcommunity, and to hear about the results of investigations carried outin the various areas of the mission over the last four years.
The Gaia mission was proposed to ESA in 1994 as part of the Horizon 2000 long-term plan, supported by the Survey Committee if the achievement of 10-microarcsec level accuracies (at 15 mag) could be demonstrated, and approved by ESA's advisory committees in 2000 after a two-year concept and technology study. During 2002, as a cost reduction exercise, the satellite constraints were modified for accommodation in the smaller Soyuz-Fregat launch vehicle, with only a modest loss in astrometric accuracy. Thus the scientific goals established in 2000 - 1 billion stars to 20 mag, with accuracies of 10 microarcsec at 15 mag, multi-epoch, multi-colour (4 broad and 11 medium band) photometry for all objects; and radial velocities to 1-10 km/s down to 16-17 mag - remain applicable. A selection of some of the papers presented is given here to provide a flavour of the meeting.
The Symposium was opened by the Director of the Paris Observatory, Daniel Egret, and Jean Kovalevsky, who stressed the great challenges and scientific rewards of Gaia. ESA's Director of Science, David Southwood, presented Gaia in the context of the current ESA science programme. These were followed by presentations of the satellite status by study manager Oscar Pace, the overall Gaia scientific case (Mignard), an overview of the mission (Perryman), the operational principles (Lindegren), accuracy assessment (de Bruijne), and the radial velocity instrument (Katz, Cropper). Presentations were made on the science impacts expected from the mission, including distance scale (Bono), Galaxy dynamics (Binney), Galaxy structure and evolution (Vallenari, Nissen, Haywood, Spite), stellar physics (Lebreton), dark matter (Wilkinson), atmospheric parameters (Recio-Blanco), exoplanets (Queloz).
Activities and overall progress of the 14 scientific working groups formed a major part of the symposium. Presentations covered the relativistic aspects of the data analysis (Klioner), simulations on planet detections (Lattanzi), duplicity and masses (Pourbaix, Soderhjelm), near-Earth asteroids (Hoeg), variability analysis (Eyer), scientific alerts (Wyn Evans), solar system studies (Muinonen, Cellino, Tanga), on-board detection (Arenou), the photometric systems (Jordi), classification (Bailer-Jones), and the quasar reference frame (Claeskens).
Various reports on the massive data analysis preparations gave a detailed perspective on the complexities and challenges facing the on-ground data treatment: the overall simulation chain (Luri, Babusiaux), the current prototype data analysis system (Torra), Grid-related studies (Ansari), and the photometric data analysis (Brown).
Five participants accepted the delicate challenge of summarising the poster presentations in the various categories: Katz, Bastian, Mignard, Breger, and Luri. This effort contributed significantly to the coverage of a large variety of topics in a limited period of time, and was greatly appreciated by the participants.
Several institute directors, including the ESO Director General, participated in the meeting, underlining the long-term strategic importance of Gaia in astronomy. Tim de Zeeuw (Leiden) treated the participants to 30-minutes of inspiring "Concluding Remarks", underlining the strength of the Gaia scientific case, setting Gaia science in the context of astrophysics in the years 2015-20, and acknowledging the huge progress made in the mission definition over the last four years (see http://www.rssd.esa.int/Gaia).
A highlight of the Symposium was the award by the Paris Observatory of the degree of Doctor Honoris Causa to the Honorary Chair of the Scientific Organising Committee, Adriaan Blaauw, who celebrated his 90th birthday earlier in the year. The Symposium dinner was held on a Seine river boat navigating Paris by night, and taking time out from the magnificent symposium setting of the Observatoire de Meudon.
The chairs of the SOC, Catherine Turon (Paris-Meudon) and Michael Perryman (ESA) were supported in the organisation of the meeting by the Gaia Science Team, an International Advisory Committee including at least one representative from each ESA member state, and an efficient Local Organising Committee, led by Yves Viala (Meudon) and supported by Karen O'Flaherty (ESA). Generous financial support by various organisations (Paris Observatory, CNES, CNRS, ESA and the Gaia industrial leading groups - EADS-Astrium and Alcatel/Alenia), permitted attendance at the symposium by an unusually large representation of younger scientists (PhDs and post-docs) many of whom are already playing a key role in the preparation of the ambitious Gaia mission. Attendees also included collaborators in Greece (recently members of ESA), and some non-member countries (Slovenia, Lithuania, Estonia, Australia). The proceedings of the symposium will be published by ESA in early 2005.Catherine Turon and Michael Perryman