The Real-time Controller (RTC) for the Narrow Field Infrared Adaptive Optics System (NFIRAOS) for TMT Final Design

摘要

The Real-Time Controller (RTC) for the Thirty Meter Telescope (TMT) Narrow Field Infrared Adaptive Optics System (NFIRAOS) is the software and server hardware that calculates wavefront corrector commands from wavefront sensor measurements. The RTC is fed data from up to six Shack-Hartmann Laser Guide Star wavefront sensors (LGS WFS), one high-order Natural Guide Star Pyramid Wavefront Sensor (PWFS), up to three Shack-Hartmann On-Instrument wavefront sensors (OIWFS) that are located in the client science instruments, and up to four on-detector guide windows (ODGW) also in the client instruments. The RTC supports laser guide star multi-conjugate adaptive optics (MCAO) and natural guide star adaptive optics (NGS AO) observing modes. The RTC controls two deformable mirrors, one conjugated to 0km (DM0, mounted on a tip/tilt stage) and another to 11.8km (DM 11). During the final design phase we used extensive prototyping to demonstrate that off-the-shelf servers using general purpose CPUs are able to support the maximum 800 Hz loop-rate at which the RTC is required to operate, with acceptable latency and jitter. Prototyping was also performed to compare the flexibility of CPU- and Xeon Phi-based architectures. This paper discusses evolution in the RTC from the Preliminary to Final Design Phases, emphasizing its modular architecture, and ability to accommodate a wide range of observing conditions.