The European Southern Observatory (ESO) in collaboration with many European institutes will start operating the Very Large Telescope Interferometer (VLTI) in 2003. Two scientific instruments, AMBER in the near-infrared and MIDI in the thermal infrared, will be offered to the European community. The expected performances of the VLTI and its instruments will be unique in terms of flux sensitivity and angular resolution, because of the large collecting area of the 8-m and 1.8-m telescopes and multiple baselines up to 200 meters. However the scientific outcome will be at the same level as the VLTI performance only if astronomers get prepared to interferometric observations and if the specialists in interferometry, including those from AMBER and MIDI, transmit their knowledge to the European astronomical community. With this objective in mind, we organize a winter school to train European astronomers to the optimal use of the VLTI and to the preparation of the first observations.

The objective of the school, beyond learning the basics of interferometry and getting acquainted to the VLTI instruments, is to get practical training of the most important tools required to prepare interferometric observations. The goal is that attendees be able to prepare an observing proposal to use  MIDI and AMBER for their own astrophysical studies.The curriculum of the school consists in general lectures for 30% of the time, practical training for 50% of it and informal seminars for the remaining time.

The school is taking place at the Centre de Physique des Houches in the first week of February 2002. The number of participants is limited to 50. The school is opened to participants of any country and any nationality. The financial support from the European Union together with other sponsors will allow us to cover most of the costs of the school (housing and travel) for all European participants. This financial aspect should prevent any student or scientist from not taking part to this school.
 
 

Scientific rationale

Interferometry will undoubtedly open a new era in optical astronomy (visible-infrared) with the advent of large interferometers. This technique invented more than a century ago, had a new birth since the 1970s when computers helped to control the numerous subsystems. Those interferometers were limited to small apertures from 10cm to 1.5m and a limited number of telescopes (2 to 3 typically). VLTI will be among new born interferometers one of the most powerful. It will operate 4 × 8-m unit telescopes and 3 × 1.8-m auxiliary telescopes. It will allow to push the boundary of current investigations from studies on multiple stellar systems and determination of stellar diameters to the fields of star formation, extra-solar planets and for the first time the study of the inner part of galaxies. Interferometers are able to probe the objects with an angular resolution 20 times better than the biggest telescopes on Earth.

Optical interferometers require some particular training since they do not directly provide images as radio interferometers do. One of the challenges of this school will be to convince astronomers that this is not an issue and that  VLTI has the potential for outstanding science. Optical interferometers are very efficient in bringing constraints on models. The measured quantities are called visibilities and correspond to the coherence of the light going through two or more separated telescopes. To be able to reconstruct an image, one needs to sample the synthesized array with almost all possible pairs of telescope. However many investigations can be performed with the direct measure of visibilities by constraining the scenarii that the astronomers have in mind. A model that leads to an image can be converted to visibilities by a simple Fourier transform and be checked against the measures. This rigorous way of using interferometric data will be the central pivot of this school as well as the observing strategies.