A near-infrared pyramid wavefront sensor for Keck adaptive optics: real-time controller

Abstract

A new real-time control system will be implemented within the Keck II adaptive optics system to support the new near-infrared pyramid wavefront sensor. The new real-time computer has to interface with an existing, very productive adaptive optics system. We discuss our solution to install it in an operational environment without impacting science. This solution is based on an independent SCExAO-based pyramid wavefront sensor realtime processor solution using the hardware interfaces provided by the existing Keck II real-time controller. We introduce the new pyramid real-time controller system design, its expected performance, and the modification of the operational real-time controller to support the pyramid system including interfacing with the existing deformable and tip-tilt mirrors. We describe the integration of the Saphira detector-based camera and the Boston Micromachines kilo-DM in this new architecture. We explain the software architecture and philosophy, the shared memory concept and how the real-time computer uses the power of GPUs for adaptive optics control. We discuss the strengths and weaknesses of this architecture and how it can benefit other projects. The motion control of the devices deployed on the Keck II adaptive optics bench to support the alignment of the light on the sensors is also described. The interfaces, developed to deal with the rest of the Keck telescope systems in the observatory distributed system, are reviewed. Based on this experience, we present which design ideas could have helped us integrate the new system with the previous one and the resultant performance gains.

Adaptive optics with an infrared pyramid wavefront sensor at Keck

“…To effectively implement these processes in real time, a dedicated real-time controller (RTC) was developed for the PyWFS. 28 The PyWFS RTC is based on the frame work of compute and control for AO, 29 software developed by the SCExAO team for operation of their AO system, which includes a PyWFS. It is based on a series of shared memories that store the real-time AO data: the WFS signals, DM and TTM commands, reconstructed wavefront, and AO correction.…”

Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor

“…15 The implementation of pWFC described in this paper is made possible by the PYWFS RTC. 11 The RTC hardware is based on an x86 architecture linux server with a Geforce GTX 1080 ti Graphical Processing Unit; its software is based on the Compute and Control for Adaptive optics (CACAO) realtime control software package. 10 To minimize impact on the existing AO system, the PYWFS RTC interfaces with the existing Keck MGAOS RTC rather than the DM and tip/tilt hardware directly.…”

“…The new real-time controller (RTC) that supports the Keck II PYWFS is described in detail in 11 and reviewed briefly here. To avoid moving the DM cabling and to support easy switching between the PYWFS and the facility SHWFS, the PYWFS RTC interfaces with the observatory's existing wavefront controller (MGAOS, 20 developed by Microgate) rather than sending commands to the DM and tip/tilt mirror directly.…”

Adaptive optics with an infrared Pyramid wavefront sensor

“…The Pyramid RTC is integrated with the current Keck AO RTC, which is used to control the existing tip-tilt and deformable mirrors. 16 A simulation campaign of the expected performance is a key component of the design process. Figure 6 shows an example of one such simulation for the Keck Pyramid WFS.…”