Altering reality to fit our turbulence simulations… A slow descent into madness?

Self-generated turbulence and dome seeing are strong contributors to the degradation of astronomical image quality; besides the now infamous low wind effect, strange temporal power spectra, low (temporal) frequency turbulence, high (spatial) frequency turbulence and strong ground layer all point to local effects. Accounting for and including all these sources of image degradation in our modeling seems intractable. Measuring dome turbulence in telescopes as varied as CFHT, LBT, UH88 and ASTEP, we have shown that these effects are transient, stochastic, and non-stationary, and that they depend on too many environmental parameters to be causally interpreted, such as wind speed, direction, dome azimuth, heat sources, radiative cooling in the telescope structure and its (differential) thermal inertia, natural air temperature variations and partial venting. It therefore seems useless, and on top of that very difficult, to estimate realistic AO performance from simulations that would try to incorporate all these effects. Instead of trying to align our simulations to reality, we propose that we try to align reality to our simulations. Indeed, we do not have to incorporate all these effects in our simulations; we can attempt to prevent them from occurring in the first place. Fortunately, local effects can be attenuated or averted at the source but improving on passive methods requires rapid and accurate sensing of turbulence inside the telescope and dome. To this end, we have been trying to develop a "turbulence camera" for almost a decade, but it has proved difficult to design a system with a sufficiently wide field and sufficient sensitivity. In the process, we have developed AIRFLOW, a localized turbulence sensor, and recent work on a wide field wavefront sensor based on optical differentiation may open new possibilities.