Surface layer turbulence measurements on the LSST site El Peñon using microthermal sensors and the lunar scintillometer LuSci

Abstract

Results from determining the optical turbulence profile (OTP) on the LSST site, El Peñon, located on Cerro Pachón (Chile) are presented. El Peñón appears to be an excellent observatory site with a surface layer seeing contribution on the order of 0.15" with most of this seeing being produced below 20m. These measurements also helped to confirm that the telescope is elevated high enough above ground. As part of the LSST site characterization campaign, microthermal measurements were taken in order to determine the contribution of the surface layer turbulence to the atmospheric seeing. Such measurements are commonly used for this purpose where pairs of microthermal sensors mounted on a tower measure atmospheric temperature differences. In addition, the lunar scintillometer LuSci was installed on El Peñon for short campaigns near full moon for the same purpose. LuSci is a turbulence profiler based on measuring spatial correlation of moonlight scintillations. The comparison of the results from both instruments during simultaneous data acquisition showed a remarkable temporal correlation and very similar mean OTPs.