Performance analysis tools and results for GMT primary mirror segment active support system

The Giant Magellan Telescope (GMT) M1 Subsystem includes the seven 8.4 meter M1 (Primary) Segment Mirrors and the steel mirror cell weldments which house the mirror active support and thermal control systems. The segmented nature of the primary mirror and the requirement that each of the six off-axis segment cells be interchangeable impose requirements on the range of motion and control beyond those applicable to the M1 subsystems on 6.5m and 8.4m telescopes using the structured honeycomb mirrors.The subsystem is both technically challenging to design and costly to produce. The M1 Subsystem is allocated a large fraction of the GMT natural seeing image quality budget. Support actuator tolerances, range of motion, accuracy, and precision, as well as the ability of the thermal control system to regulate the primary mirror temperature, all have a significant effect on the image quality. The authors have developed several linear models to estimate the effect of force and moment errors at the M1 Segment Active Supports and the non-uniformity of temperature across M1 segments on the delivered image quality. These results are coupled to the Wavefront Control Subsystem model and are integrated into the GMT system-level simulations to produce a final image quality budget and to quantify the effectiveness of the Wavefront Control Subsystem to compensate for M1 Subsystem error. In this paper, we present the modeling process and preliminary performance results obtained using the models.