RESEARCH ACTIVITY

Why is the atmospherical turbulence study crucial in Astronomy  ?

From the visible up to the near and mid infrared ranges, the astronomical observations can be performed from the space as well as from the ground. In these regimes  the ground-based astronomy is particularly appealing for astronomers because of a few fundamental reasons:

1) the cost of a ground-based telescope is undoubtedly cheaper than that of a space-based telescope

2) the typical ground-based telescope
life-time is much longer than that of a space-based telescope

3) the angular resolution achievable by a ground-telescope is much better than that is achievable by a space-based telescope. The angular resolution measures the smallest detail that we can discriminate in an image obtained with a telescope and it is proportional to the inverse of the telescope pupil size (R = λ/D) where λ is the wavelength. Top-level ground-based telescopes, at present time
(D = 8-10 m), can provide a resolution typically 4-5 times better that what is achievable with the space-based Hubble telescope (D = 2.4m). Looking at the future generation of ground and space-based telescopes it appears clear that the potential  angular resolution gain for the ground-based telescopes might be even larger. The future ground-based Extremely Large Telescopes such as the European Extremely Large Telescope (E-ELT - D = 42 m) and the American Thirty Meter Telescope (TMT - D = 30 m) are, indeed, conceived to have a pupil size typically 5-6 times larger than the future space-based telescope (James Webb Space telescope - D = 6.5 m). It follows that the potential advantage for the ground-based telescopes would be even more effective.

However, this can be considered true only in absence of the atmospheric turbulence. The atmospheric turbulence, indeed, perturbs the wavefront coming from the space and, as a consequence, limits the angular resolution of whatever ground-based telescope to that of a 10 cm pupil size telescope.

We can understand therefore why, in astronomy, it is crucial and fundamental to study the atmospheric turbulence and its interaction with the light coming from the space. This is, indeed, the fundamental cause that deteriorates the information that we can retrieve from the astronomical observations. We have to eliminate the perturbations introduced by the turbulence on the wavefront to preserve the incredible performances potentially achievable by these new generation astronomical facilities. But to correct properly the turbulence effects we need to know the atmospheric turbulence.

This research line intends to study the nature of the turbulence, develop instruments and/or techniques able to quantify all the turbulence features and its effects on the wavefronts. Besides, the atmospheric non-hydrostatic mesoscale models offer the incredible great opportunity to reconstruct the whole life of the turbulence starting from the instant in which it is triggered (birth) up to when it vanishes (death). Also these models, as well as general Circulation Models, permit us to study the environment conditions that facilitate and/or attenuate the triggering of the turbulence.

The main research topics in which ForOT is involved on are:


OPTICAL TURBULENCE AND ENVIRONMENTAL CONDITIONS

MODELLING WITH ATMOSPHERICAL NON-HYDROSTATIC MESOSCALE MODELS

OPTICAL TURBULENCE PARAMETERIZATION IN STABLE REGIMES

OPTICAL TURBULENCE MEASUREMENTS - SITE TESTING

DEVELOPMENT OF TECHNIQUES FOR  OPTICAL TURBULENCE MEASUREMENTS

APPLICATIONS TO THE ADAPTIVE OPTICS



  E.Masciadri, 11/2009