A G-SCIDAR for Ground-Layer Turbulence Measurements at High Vertical Resolution

We propose a new method based on the generalized SCIDAR principle to characterize the vertical distribution of the turbulence in the first few hundred meters above the telescopewith a better vertical resolution than usually achievable by such an instrument. Using a wide binary star (35" separation) and analyzing the spatio- temporal cross-correlation images, we achieve a C 2 profile with a vertical resolution of a few tens of meters. We present the principle and the data-reduction process of this method and show first results obtained with a SCIDAR instrument mounted to the Vatican Advanced Technology Telescope (VATT) on the top of Mount Graham. As an application, we estimate the fraction of the turbulence between the dome of the VATTand the primary mirror of the Large Binocular Telescope.