Adaptive Optics in Integrated Modeling of Telescopes

Sammanfattning: This thesis present the implementation of a modular adaptive optics (AO) model, as part of an integrated model of extremely large telescopes (ELTs). The purpose of the project has been to establish knowledge within integrated modeling, with emphasis on adaptive optics. A modular Single Conjugate Adaptive Optics (SCAO) model has been built in MATLAB, around ordinary differential equation (ODE) solvers. The architecture of the model and numerical methods for the subsystem models are presented. Non-linearities, such as CCD effects, mirror stroke saturation and misalignments are modeled and support for CCD mode handling is included in the ODE solvers. The model handles mirror dynamics and integration of the wavefront sensor CCD. Disturbances from atmosphere and CCD noise sources are included. The model supports a layered atmosphere and both geometrical and Fresnel propagation for near vertical paths. Multiple guide stars and wavefront sensors can be used, facilitating ground layer adaptive optics (GLAO) with natural guide stars. The model can be run in a basic mode, where the dynamics of the mirrors and the CCD modes are modeled with delays, and the wavefront sensor measurements are performed on the wavefront directly. A full model is run with 10 or more integration steps per AO sample time interval, and is including mirror dynamics and Fraunhofer propagation from the subapertures to the subimages. The model is modular and all data passed between modules are reachable outside the modules and can be saved for post-processing. Post-processing routines, using the data for studies of point spread functions in other directions or at other wavelengths are included, as are many small utility routines for visualization of result. The SCAO model has been implemented as part of the Euro50 integrated model, developed by the telescope group at the Lund Observatory. The full wavefront sensor model has been parallelized, introducing options for switching between single mode and parallel mode. Methods for parallelization of the integrated model, within the MATLAB environment, are discussed. A basic version of the model has been adapted to the integrated model of the European Extremely Large Telescope (E-ELT) and results from simulations with this model are presented. A model of SCAO of the existing Vacuum Tower Telescope (VTT), which has been used to test control strategies for the telescope SCAO system, is also presented.