Integrated Modeling of NFIRAOS: Characterizing performance in the presence of vibra tion

The Narrow Field InfraRed Adaptive Optics System (N FIRAOS) will be the first-light facility Multi-Conj ugate Adaptive Optics (MCAO) system for the Thirty Meter Telescope (TMT). Historically, an important factor limiting the performance of an AO system has been the system vib rations and their impact on the delivered image qua lity. In order to leverage the extraordinary capabilities of the TMT, NFIRAOS must be capable of meeting the required op tical performance and stability specifications while oper ating in the presence of the predicted vibration en viro ments. Using the NRC-developed integrated modeling framework (NR Cim), a detailed evaluation of the dynamic opto-mec hanical performance of NFIRAOS was completed with several s ources of structural disturbances (vibration from t he elescope structure, from attached instruments, and internal to NFIRAOS). Multiple computational methodologies, including transient (time-series) and harmonic (transfer func tio ) analyses combined with a Linear Optics Model (LOM), together with control system transfer functions for both com mon path and non-common-path disturbances were used to valuate and compare the NFIRAOS delivered image quality. T hese procedures are described and the NFIRAOS perfo rmance in the presence of the various sources of vibration ar e reported. These sources include observatory vibr ation transmitted to NFIRAOS as well as internal sources such as the LGS WFS trombone, refrigeration, client instruments’ r otator and cable wrap.