Abstract:
The Indian Institute of Astrophysics is developing a Multi-Conjugate Adaptive Optics
system for the Kodaikanal Tower Telescope. In this context, we measured the daytime turbulence strength profile at the Kodaikanal Observatory. The first method
based on wavefront sensor images, called solar differential image motion monitor+, was used to estimate the higher altitude turbulence up to a height of 5 to 6 km.
The second method used balloon-borne temperature sensors to measure the nearEarth turbulence up to 350 m. We also carried out simulations to validate the performance of our system. We report the first-ever daytime turbulence strength profile
measurements at the observatory. We identified the presence of a strong turbulence
layer ∼3 km above the observatory. The measured near-Earth turbulence matches
the trend that is expected from the model for a daytime component of turbulence and
gives an integrated r 0 of ∼4 cm at 500 nm. This is consistent with earlier seeing
measurements. This shows that a low-cost setup with a small telescope and a simple array of temperature sensors can be used for estimating the turbulence strength
profile at the site.
