Edward J. Younger

MOAO first on-sky demonstration with CANARY

Context. A new challenging adaptive optics (AO) system, called multi-object adaptive optics (MOAO), has been successfully demonstrated on-sky for the first time at the 4.2 m William Herschel Telescope, Canary Islands, Spain, at the end of September 2010. Aims. This system, called CANARY, is aimed at demonstrating the feasibility of MOAO in preparation of a future multi-object near infra-red (IR) integral field unit spectrograph to equip extremely large telescopes for analysing the morphology and dynamics of high-z galaxies. Methods. CANARY compensates for the atmospheric turbulence with a deformable mirror driven in open-loop and controlled through a tomographic reconstruction by three widely separated off-axis natural guide star (NGS) wavefront sensors, which are in open loop too. We compared the performance of conventional closed-loop AO, MOAO, and ground-layer adaptive optics (GLAO) by analysing both IR images and simultaneous wave-front measurements. Results. In H-band, Strehl ratios of 0.20 are measured with MOAO while achieving 0.25 with closed-loop AO in fairly similar seeing conditions (r 0 ≈ 15 cm at 0.5 μm). As expected, MOAO has performed at an intermediate level between GLAO and closed-loop AO.

Experience with wavefront sensor and deformable mirror interfaces for wide-field adaptive optics systems

Recent advances in adaptive optics (AO) have led to the implementation of wide field-of-view AO systems. A number of wide-field AO systems are also planned for the forthcoming Extremely Large Telescopes. Such systems have multiple wavefront sensors of different types, and usually multiple deformable mirrors (DMs). Here, we report on our experience integrating cameras and DMs with the real-time control systems of two wide-field AO systems. These are CANARY, which has been operating on-sky since 2010, and DRAGON, which is a laboratory AO real-time demonstrator instrument. We detail the issues and difficulties that arose, along with the solutions we developed. We also provide recommendations for consideration when developing future wide-field AO systems.

The SALT HRS spectrograph: instrument integration and laboratory test results

SALT HRS is a fibre-fed, high dispersion échelle spectrograph currently being constructed for the Southern African Large Telescope (SALT). In this paper we highlight the performance of key optical components, describe the integration tasks that have taken place and present some first light results from the laboratory. The instrument construction is well advanced and we report on the attainment of the required mechanical and thermal stability and provide a measurement of the input optics performance (including the fibre feed). The initial optical alignment of both the fibre input optics, including image slicers, and the spectrograph optics has taken place and is described.

Status update of the CANARY on-sky MOAO demonstrator

The CANARY on-sky MOAO demonstrator is being integrated in the laboratory and a status update about its various components is presented here. We also discuss the alignment and calibration procedures used to improve system performance and overall stability. CANARY will be commissioned at the William Herschel Telescope at the end of September 2010.

An ELT scale MCAO real-time control prototype using Xeon Phi technologies

With the next-generation of Extremely Large Telescopes (ELTs), the demands of adaptive optics real-time control (AO RTC) increase massively compared to the most complex AO systems in use today. Green Flash, an ongoing EU funded project, is investigating the optimal architecture for ELT scale AO RTC, with an emphasis on GPU and many core CPU solutions. The Intel Xeon Phi range of x86 CPUs is our current focus of investigation into CPU technologies to solve the ELT-scale AO RTC problem. Built using Intels Many Integrated Core (MIC) architecture incorporating 64 general purpose x86 CPU cores into a single CPU package paired with a large pool of on-chip high bandwidth MCDRAM, the Xeon Phi includes many of the advantages of current technologies. The current generation Xeon Phi is readily compatible with standard Linux operating systems and all of the tools and libraries, and as a standard socketed CPU it eliminates the latency introduced by the extra data transfers required for previous Xeon Phis and other accelerator devices. The Durham Adaptive Optics Real-time Controller (DARC) is a freely available, on-sky tested, fully modular, x86 CPU based AO RTC which which is ideally suited to be a basis for our investigation into ELT scale AO RTC performance. We present a proof of concept AO RTC system, in collaboration with the Green Flash project, for ELT scale MCAO, with the requirements of the MAORY AO system in mind, using an optimised DARC on Xeon Phi hardware to achieve the required performance.

DRAGON: a wide-field multipurpose real time adaptive optics test bench

DRAGON is be a new and in many ways unique visible light adaptive optics test bench. Initially, it will test new and existing concepts for CANARY, the laser guide star tomographic adaptive optics demonstrator on the WHT, then later it will be used to explore concepts for other existing and future telescopes. Natural and Laser Guide Stars (NGS and LGS) are emulated, where the LGSs exhibit the effects of passing up through turbulence and spot elongation. AO correction is performed by one high and one low order deformable mirror, allowing woofer-tweeter control, and multiple high and low order wave front sensors detect wave front error. The Durham Adaptive Optics Real-time Controller (DARC) is used to provide real-time control over various DRAGON configurations. DRAGON is currently under construction, with the turbulence simulator completed. Construction and alignment of the system is expected to be finished in the coming year, though first results from completed modules follow sooner.

Prototyping AO RTC using emerging high performance computing technologies with the Green Flash project

The Green Flash initiative responds to a critical challenge in the astronomical community. Scaling up the real-time control solutions of AO instruments in operation to the specifications of the AO modules at the core of the next generation of extremely large telescopes is not a viable option. The main goal of this project is to design and build a prototype for an AO RTC targeting the E-ELT first-light AO instrumentation. We have proposed innovative technical solutions based on emerging technologies in High Performance Computing, assessed this enabling technologies through prototyping and are now assembling a full scale demonstrator to be validated with a simulator and eventually tested on sky. In this paper, we report on downselection process that led us to the final prototype architecture and the performance of our full scale prototype obtained with a real-time simulator.

Green FLASH: energy efficient real-time control for AO

The main goal of Green Flash is to design and build a prototype for a Real-Time Controller (RTC) targeting the European Extremely Large Telescope (E-ELT) Adaptive Optics (AO) instrumentation. The E-ELT is a 39m diameter telescope to see first light in the early 2020s. To build this critical component of the telescope operations, the astronomical community is facing technical challenges, emerging from the combination of high data transfer bandwidth, low latency and high throughput requirements, similar to the identified critical barriers on the road to Exascale. With Green Flash, we will propose technical solutions, assess these enabling technologies through prototyping and assemble a full scale demonstrator to be validated with a simulator and tested on sky. With this R&D program we aim at feeding the E-ELT AO systems preliminary design studies, led by the selected first-light instruments consortia, with technological validations supporting the designs of their RTC modules. Our strategy is based on a strong interaction between academic and industrial partners. Components specifications and system requirements are derived from the AO application. Industrial partners lead the development of enabling technologies aiming at innovative tailored solutions with potential wide application range. The academic partners provide the missing links in the ecosystem, targeting their application with mainstream solutions. This increases both the value and market opportunities of the developed products. A prototype harboring all the features is used to assess the performance. It also provides the proof of concept for a resilient modular solution to equip a large scale European scientific facility, while containing the development cost by providing opportunities for return on investment.

A modular design for the MOSAIC AO real-time control system

The proposed MOSAIC first-generation instrument for the ELT is a multi-object spectrograph utilising a combined MOAO and GLAO system. With 8 separate wavefront sensors (4 LGS and 4 NGS), and 10 separate deformable mirrors, in addition to the ELT M4 mirror, MOSAIC represents one of the most challenging ELT instruments for real-time control, using a total of approximately 65,000 slope measurements to control approximately 26,000 actuators with a 250 Hz LGS frame rate. The proposed modular design of real-time control system to be used with MOSAIC is presented. This is based on the Durham AO Real-time Controller (DARC), and uses 12x Intel Xeon Phi nodes (6U rack space, approx 2.5 kW under load) to obtain the required performance. We describe the prototyping activities performed at Durham, including estimates of AO system latency and jitter. The design challenges are presented, along with the techniques used to overcome these. The full modular architecture is described, including the system interfaces, control and configuration middleware, telemetry subsystem, and the hard real-time core pipeline. One benefit of our design is the ability to simultaneously test different AO control algorithms, which represents a significant opportunity for automatic optimisation of AO system performance. We discuss this concept, and present an artificial neural network solution for machine learning, which can be used to automatically improve MOSAIC performance with time. Algorithms that can be optimised in this way are discussed, include pixel calibration and processing techniques, wavefront slope measurement routines, wavefront reconstruction techniques and associated parameters, and temporal filtering methods, including vibration control. The hardware design for the real-time control system is presented, including an overview of the network architecture, the interconnections between computational nodes, and the method by which all pixels from all 8 wavefront sensors are processed concurrently.

Phase A AO system design and performance for MOSAIC at the ELT

MOSAIC is a mixed-mode multiple object spectrograph planned for the ELT that uses a tiled focal plane to support a variety of observing modes. The MOSAIC AO system uses 4 LGS WFS and up to 4 NGS WFS positioned anywhere within the full 10 arcminute ELT field of view to control either the ELT M4/5 alone for GLAO operation feeding up to 200 targets in the focal plane, or M4/5 in conjunction with 10 open-loop DMs for MOAO correction. In this paper we present the overall design and performance of the MOSAIC GLAO and MOAO systems.