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The Mid-infrared ELT Imager and Spectrograph (METIS) is is one of three first-generation science instruments
for the Extremely Large Telescope (ELT) and has recently completed its final design phase. Its Single Conjugate
Adaptive Optics (SCAO) system will provide the performance of an extreme adaptive optics system which enables
high contrast imaging observations in the thermal/mid-infrared wavelength domain (3 μm – 13.3 μm).
The Real-Time Computer (RTC) is the central component of the SCAO real-time control system. It executes
the time critical wavefront control loop as well as associated control tasks by processing the data from the
pyramid wavefront sensor and controlling the set of ELT actuators dedicated to adaptive optics. A total of up to
4,866 commands to be computed at a loop rate of up to 1 kHz imposes a number of demanding constraints in
terms of memory throughput and computing power on the Hard Real-Time Core (HRTC), which employs GPU
acceleration for the bulk of computations.
Several auxiliary functions need to be in place to establish and maintain the quality of the wavefront correction.
Among them are the control of the pupil position, the compensation of misregistration and of non-common path
aberration, and the adaptation of the temporal control parameters.
The main wavefront control loop has been prototyped to verify timing requirements. A median RTC
computation time of 382 μs was achieved for a 300k samples (5 minutes) run. The results are presented in this
paper together with the foreseen RTC hardware and the software deployment within the SCAO Control System
