Generalized SCIDAR measurements at La Silla Observatory

Abstract

ABSTRACT. We present the results of vertical profiles of refractive index structure constant C n2 (h) measurements made at the 1-m telescope, La Silla Observatory (ESO,Chile) using the gene ralized SCIDAR technique. Obse rvations took place during July, August, November, 2002 an d February 2003. The instrume ntation, computer interface and a preliminary reduction software were provided by the Imperial College (London) scientific group. We describe the SCIDAR image processing technique and two inverting methods. The first, proposed by the Imperial College group, is based on the Tikhonov regularization and the second, on use at Nice University, is based on maximum entropy. Performances of both methods agree well. The profile integrals are compared to simultaneous DIMM seeing measurements made at La Silla Observatory. INTRODUCTION. Generalized SCIDAR (Scintilla tion Detection and Ranging) is one of the most effective methods to measure the altitude distribution of optical turbulence in the atmosphere above the site. With this instrument installed on the telescope a diameter of which is preferably not below 1m for the best altitude resolution (about 200-300 meters) we observe the diffraction patterns images from a binary star on the telescope pupil produced by an atmospheric turbulence. Then we recover a profile of the refractive index structure constant C