Multi-instrument measurement campaign at Paranal in 2007

Characterization of the outer scale and the seeing of the surface layer

¹ OCA. CNRS UMR 6525 Hippolyte FIZEAU, Université de Nice-Sophia Antipolis, Campus Valrose, 06108 Nice Cedex 2, France
e-mail: daliali@unice.fr
² European Southern Observatory, Karl-Schwarzschild-Str.2, 85748 Garching, Germany
³ Instituto de Astrofísica de Canarias via Lactea s/n, 38200 La Laguna, Tenerife, Spain
⁴ Cerro Tololo Inter-American Observatory, Casilla 603 La Serena, Chile
⁵ Département de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montreal, QC, H3C 3J7, Canada

Received: 8 June 2010
Accepted: 5 September 2010

Abstract

Aims. Within the framework of site qualification for the future European large telescope E-ELT, a campaign of measurements was carried out for ten nights in December 2007 at Paranal using six independent instruments.

Methods. To characterize the optical turbulence, two techniques were used: the statistical analysis of the fluctuations of the angle of arrival and the scintillation of the observed objects which are, in this case, a single star for DIMM, GSM, and MASS, a double star for Cute-SCIDAR, and Moon limb for MOSP and LuSci.

Results. The optical parameters measured in this campaign and presented here are the seeing, the isoplanatic angle, the coherence time, and the outer scale. We obtain a good agreement with the value measured in previous campaigns. We also extracted the vertical profile of the turbulence given by , and the profiles of the outer scale for the first time at Paranal. A comparison of the different results that we present here allows the determination of the energy distribution in the free atmosphere, on the ground layer as well as in the first meters above ground. This reveals a significant contribution of the surface layer to the degradation of the global seeing.