Linear controller error budget assessment for classical adaptive optics systems.

Abstract

Understanding limitations of adaptive optics (AO) systems is crucial when designing new systems. In particular, analyzing the potential of different controllers is of great interest for the upcoming AO systems of the very large telescopes (VLTs) and extremely large telescopes (ELTs). This paper thus details a complete error budget assessment formalism, based on analytic formulas involving the disturbance temporal power spectral density (PSD) and the controller transfer function, and is applicable to any linear controller. This formalism is presented here for the special case of classical AO systems, but can be extended to any closed- or open-loop, single- or multi-conjugated AO configuration. Special attention is paid to the "control-dependent" errors, the importance of which is directly related to the type of control used in the AO system. The proposed method is applied to a NAOS/VLT-type single conjugated AO system, using disturbance PSD derived from a simulated turbulence trajectory or estimated from wavefront sensor measurements, enabling the construction of detailed error budgets for an integrator and different linear quadratic Gaussian controllers. Application to ELT-sized systems is discussed in the conclusion.