The GSM mission to Paranal was highly successful and for the first time provided statistical data on the outer scale at this site. Our main results consist in the following:
Turbulent energy in the SL contributes an average amount of only 12.5% to the total turbulent energy detected by GSM along the line of sight. This corresponds to an average seeing degradation around 8% if turbulence effects in the SL are added to the turbulence above 21 m. While unit telescopes of the VLT are not affected by these layers, the situation will not be the same for auxiliary telescopes (ATs) of the VLTI which have been designed closer to the ground (4.5-6.5 m). Hence, continuous micro-thermal monitoring at Paranal appears to be desirable to study the local effects in detail and to evaluate their importance for the site seeing and particularly for the ATs;
The analysis of the spatio-temporal cross-correlations of the AA fluctuations can lead to the detection of the atmospheric layers (Avila et al. ). From the AA cross-correlations one can estimate the number of predominant turbulent layers, their respective strengths, the velocity and direction of the wind which carries the turbulent eddies. The principle of the wind measurement with GSM is given in Conan et al. (). The full wind analysis and cross-correlation interpretation must include simultaneous comparisons with other parameters, , and . The methods of such complete analysis are still under development.
The success of this observing campaign is a result of a long and tedious preparatory work done at the Département d'Astrophysique of the Nice University. We acknowledge the efforts of A. Robini, J.-F. Manigault and M. Azouit in the development of GSM and of the mast equipment, and the help of the staff of the "Observatoire de la Côte d'Azur''. On-site preparation of GSM campaign at Paranal was organized and implemented by ESO under the supervision of M. Sarazin. We are indebted to Francisco Gomez for helping with observations during the second half of the mission.
Financial support came essentially from INSU, CNRS and MENRT for development of GSM experiment, and from ESO for this measurement campaign.
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