Forward modelling of turbulence strength profile estimation using S-DIMM+

Abstract

Knowledge of the refractive index structure constant profile at an astronomical site is crucial before developing a Multi-Conjugate Adaptive Optics (MCAO) system at that site. The S-DIMM+ (S-Differential Image Motion Monitor+) method proposed by Scharmer and van Werkhoven1 uses the images recorded by a SHWFS (Shack- Hartmann Wavefront Sensor) to estimate the profile. We have performed simulations of the same using simulated solar granulation images (which are the “objects”) and multiple layers of the atmosphere characterised by Kolmogorov turbulence, a telescope of given aperture and finally a SHWFS. The images formed using the SHWFS are then processed using an inversion code developed by us to get the turbulence strength profile. We found that the code was able to invert the data satisfactorily upto a height of 10 km with our system parameters.