# A many-core CPU prototype of an MCAO and LTAO RTC for ELT-scale instruments

## TL;DR

This paper presents a many-core CPU architecture for ELT-scale adaptive optics real-time control, demonstrating low latency and jitter performance across SCAO, MCAO, and LTAO modes using simulated data.

## Contribution

The paper introduces a novel many-core CPU architecture tailored for ELT-scale AO RTC, capable of handling complex modes with low latency and high flexibility.

## Key findings

- Achieved < 600μs latency in SCAO mode with Shack-Hartmann WFS
- Achieved < 800μs latency in SCAO mode with Pyramid WFS
- Full system latency < 1000μs with jitters < 40μs RMS in MCAO and LTAO modes

## Abstract

We propose a many-core CPU architecture for Extremely Large Telescope (ELT) scale adaptive optics (AO) real-time control (RTC) for the multi-conjugate AO (MCAO) and laser-tomographic AO (LTAO) modes. MCAO and LTAO differ from the more conventional single-conjugate (SCAO) mode by requiring more wavefront sensor (WFS) measurements and more deformable mirrors to achieve a wider field of correction, further increasing the computational requirements of ELT-scale AO. We demonstrate results of our CPU based AO RTC operating firstly in SCAO mode, using either Shack-Hartmann or Pyramid style WFS processing, and then in MCAO mode and in LTAO mode using the specifications of the proposed ELT instruments, MAORY and HARMONI. All results are gathered using a CPU based camera simulator utilising UDP packets to better demonstrate the pixel streaming and pipe-lining of the RTC software. We demonstrate the effects of switching parameters, streaming telemetry and implicit pseudo open-loop control (POLC) computation on the MCAO and LTAO modes. We achieve results of < 600$\mu$s latency with an ELT scale SCAO setup using Shack-Hartman processing and < 800$\mu$s latency with SCAO Pyramid WFS processing. We show that our MCAO and LTAO many core CPU architecture can achieve full system latencies of < 1000$\mu$s with jitters < 40$\mu$s RMS. We find that a CPU based AO RTC architecture has a good combination of performance, flexibility and maintainability for ELT-scale AO systems.