New On-sky results from FASS

Abstract

FASS (Full Aperture Scintillation Sensor) provides estimates of Cn2 profiles, together with seeing, coherence time, Fried parameter and isoplanatic angle. The monitor is meant for site testing and to support operations of very large telescopes and future ELTs. The key components of the instrument are a low-noise camera (sCMOS or CCD) attached to a portable telescope (9.5” or 12”) that together with a customized optics, processes scintillation images. These “flying shadows” or speckles are subsequently processed to get their power spectra that, fitted to a linear combination of previously simulated scintillation images from single turbulence layers located at different altitudes, yield estimates of stratified turbulence strengths.We present new results using on-sky data provided by a basic optical set-up, configured for the free-atmosphere case (𝑧>500𝑚𝑚). The results are compared to profiles simultaneously acquired from a stereo-SCIDAR instrument installed in one of Paranal AT telescopes and from MASS/DIMM estimates. Despite a non-optimal optical configuration, encouraging results have been obtained during 2018 campaigns at Paranal observatory