Wave Optics Simulations of a Dual Beacon Hartmann Turbulence Sensor

Abstract

Wave optics were used to simulate a dual beacon Hartmann Turbulence Sensor (HTS). The system simulated was used experimentally to measure turbulence profiles. These simulations were intended to help explain differences between the experimental results and theoretical predictions. The theoretically predicted results presume weak turbulence, a Kolmogorov power spectrum for the turbulence, and a geometric optics derived weighting of the turbulence along the path. The simulations carried out used a modified von Kármán spectrum, with finite inner and outer scales, so the effects of these scales could be readily studied. A number of interesting results were obtained. The simulations resulted in lower tilt variances in the HTS subapertures than expected, but this had little end effect on the turbulence profiles produced. The effect of the inner and outer scales on this point will be discussed. The profiling technique proved to be powerful enough to sometimes resolve individual phase screens used in simulation. While this result is very interesting, it points to the challenges in simulating a system like this, rather than any difference between theory and experiment. Finally, while the geometric optics presumption is seen as ignoring diffraction, no conclusion on the differences between theory and experiment (or simulation) based upon this point was made. The simulations concentrated on simulating an actual HTS system with a 32 × 32 subaperture array on a 16″ telescope at a 1 km range.