"Science Driver"

Optical Turbulence’ (OT) is the term employed in astronomical field to refer to the turbulence affecting the spatial and angular resolution of images obtained at ground-based telescopes foci. Fluctuations of temperature induce fluctuations of the refractive index and, finally, to fluctuations of the amplitude and phase of wavefronts (electromagnetic field) coming from astrophysical objects located in the faraway space. The origin of optical turbulence is therefore somehow different from the dynamic turbulence (having a mechanic origin) that is familiar to physicists of the atmosphere. On the other side, optical and dynamic turbulence are strictly physically related.

The optical turbulence is, by far, one of the main causes limiting the observational ground-based astronomy (OGBA) performances. The future and the success of the OGBA strongly depend on our ability (1) in characterizing the optical turbulence at the summit of the astronomical sites from a qualitative as well as quantitative point of view, (2) in improving our knowledge on the mechanisms producing and developing the optical turbulence (3) in predicting 3D maps of the optical turbulence to optimize the flexible-scheduling of scientific programs and instruments placed at foci of telescopes and (4) in correcting wave-front perturbations produced by the atmospheric turbulence.

Several among the most challenging scientific programs to be carried out with ground-based telescopes and aiming to enhance our understanding of Universe require excellent turbulent conditions to be successfully performed. Competitiveness of ground-based astronomy with respect to the space-based one is strictly related to our ability in identifying and predicting such a temporal window in the most accurate way. On the front of the Adaptive Optics (AO) techniques, new sophisticated methods (MCAO, GLAO, LGS) conceived to optimize the perturbed wave-fronts correction on different field of view and to optimize the efficiency of their employment require today a more detailed knowledge of the vertical distribution of the OT (not only integral values). This new generation AO requires a more detailed study of the Point Spread Function (PSF) morphology (for wide as well as narrow fields) and a comprehension of its connection with different parts of the turbulent spectrum. Interferometry can suffer from some further/different limitations due to the turbulence. AO and Interferometry can, at the same time, provide some sort of characterization of the turbulence itself. Some specific topics such as the precise nature and role played by the spatial coherence outer scale in the High Angular Resolution (HAR) techniques, the turbulence spectrum features in non-Kolmogorov regimes , are still theatre of discussion at present, and a more genuine scientific debate is suitable to better define the frontiers of the theory in this field.

The Operational Numerical Weather Prediction (NWP) systems at medium and mesoscale range might play an important role for ground-based astronomy in the next decades. 4D-Var Assimilation Data employing satellites measurements recently strongly improved the quality of the Medium Range Weather Forecasts. A new challenge for the meteorology appeared at the horizon: the Mesoscale Data Assimilation. This consists on a network of surface stations and a mesoscale assimilation system with a resolution of a few kilometers. Such a system is mandatory to improve the ability of mesoscale models in reconstructing the unresolved physical parameters (such as the optical turbulence) evolving at spatial and temporal scales smaller than the model resolution and to improve the accuracy of meteorological weather forecasts extended on limited surfaces. How this can be set up in remote regions of the earth such as those typically interesting for astronomers ?

Aims of this International Conference is to join researchers (astronomers, physicists, meteorologists) to discuss about how to face the ground-based astronomy new era from the point of view of the TURBULENCE putting in evidence the main challenges and critical points. We exhort specialists in each field (instrumentation, modeling, theory, AO simulations and systems) to highlight their new results as well as the open questions/problems/anomalies raised up in their researches. We wish to give to this meeting the framework of an experiment aiming to enforce new typologies of collaborations enhancing interdisciplinary and cross-field interactions. A special session will be dedicated to an open discussion with the participation of a few scientists who lead a few among the most powerful ground-based facilities from which the success of future ground-based astronomy will depend on and scientists leading operational forecasts systems and/or experts in specific key topics.

Contributions on the following topics are welcome:

- Instruments, measurements, site testing survey of optical and dynamic turbulence
- Optical turbulence in the troposphere and stratosphere
- Optical Turbulence Data Base
- Inter-comparison measurements from different instruments, standardization of instruments
- Calibration: Instruments and Atmospheric Models
- Optical turbulence modeling and forecasts
- Turbulence closure schemes for night stable conditions
- Data Assimilation: GCM and mesoscale models

- Operational Models: GCM and mesoscale models

- AO and optical turbulence: simulations with analytic and Monte Carlo models
- PSF morphology (wide and narrow field) vs. turbulence
- MCAO, GLAO, LGS vs. turbulence
- Flexible-scheduling: strategies, present systems, lessons learnt, quantification of the scheduling efficiency