SCIDAR measurements at Pic du Midi

We present SCIDAR measurements made at the Pic du Midi Observatory with PIS CO. A series of vertical profiles of the refractive-index structure constan t C-N(2)(h) was obtained with the observations of the binary stars gamma an d gamma Ari, with 30 second time sampling. In the free atmosphere, the turb ulence was dominated by the contribution of a few well-separated atmospheri c layers at altitudes in the range 8-20 km, with significant changes within a few minutes. We describe a new method based on the CLEAN algorithm appli ed on the 2-D covariance function of the irradiance fluctuations in the pup il plane and compare it with the widely-used Maximum Entropy Method applied on a slice of this 2-D function. Our method is much less sensitive to the noise. Vertical profiles of the wind velocity and direction were obtained w ith an automatic procedure working on the mean cross-correlation function o f consecutive frames. Furthermore, we validate a model for the SCIDAR detec tivity threshold in terms of distance to the turbulent layers.