The First Solar Seeing Profile Measurement with Two Apertures and Multiple Guide Regions

Abstract

Ground-based observations suffer from atmospheric turbulence perturbations, which seriously degrade the image quality. The seeing profile associated with the turbulence is critical to characterize an astronomical site. The optimal design and performance estimation of future solar ground-layer adaptive optics (GLAO) and multi-conjugate adaptive optics (MCAO) heavily rely on our knowledge of the seeing profile at a specific site. Many current optical seeing profile measurement techniques require one to use a large solar telescope for that purpose. The development of a portable instrument to measure and characterize the seeing profile is thus highly needed, in particular for testing potential new sites or for the regularly monitoring of the seeing condition at existing sites. Recently, we proposed the Advanced Multiple Aperture Seeing Profiler (A-MASP), which uses multiple small telescopes and multiple regions of interest (ROIs) on the solar surface to measure the seeing profile up to an altitude of 30 km. Here, we report our recent proof-of-concept observation run of the A-MASP technique with the Dunn Solar Telescope (DST) of the National Solar Observatory (NSO). We found that the Fried parameter, $r_{0}$, was about 12 cm at the observed wavelength of 630 nm in the early morning and that there were three main turbulence layers. The strongest one was the mix layer near the ground. We observed the evolution of the top of the mix layer and found that it can rise to about 1.5 km in about 18 min, which is consistent with the theory of daytime boundary layer evolution. Another turbulence layer was observed from 8 to 15 km, which is at the top of the convective layer. Comparing an instrument with two sub-apertures with a real A-MASP instrument, we found that they should lead to similar results except for the altitude $h = 0$.