Progress on the VLT Adaptive Optics Facility

2006

The Adaptive Optics Facility is a project to convert UT4 into a specialised Adaptive Telescope. The present secondary mirror (M2) will be replaced by a new M2-Unit hosting a 1170-actuator deformable mirror. The three focal stations will be equipped with instruments adapted to the new capability of this UT. Two instruments have been identified for the two Nasmyth foci: Hawk-I with its AO module GRAAL allowing a Ground Layer Adaptive Optics correction and MUSE with GALACSI for GLAO correction and Laser Tomography Adaptive Optics correction. A future instrument still needs to be defined for the Cassegrain focus. Several guide stars are required for the type of adaptive corrections needed and a Four Laser Guide Star Facility (4LGSF) is being developed in the scope of the AO Facility. Convex mirrors like the VLT M2 represent a major challenge for testing and a substantial effort is dedicated to this. ASSIST, is a test bench that will allow testing of the Deformable Secondary Mirror and b...

Journal of Astronomical Telescopes, Instruments, and Systems, 2018

We demonstrate a novel architecture for Adaptive Optics (AO) control based on FPGAs (Field Programmable Gate Arrays), making active use of their configurable parallel processing capability. SPARC's unique capabilities are demonstrated through an implementation on an off-the-shelf inexpensive Xilinx VC-709 development board. The architecture makes SPARC a generic and powerful Real-time Control (RTC) kernel for a broad spectrum of AO scenarios. SPARC is scalable across different numbers of subapertures and pixels per subaperture. The overall concept, objectives, architecture, validation and results from simulation as well as hardware tests are presented here. For Shack-Hartmann wavefront sensors, the total AO reconstruction time ranges from a median of 39.4µs (11 × 11 subapertures) to 1.283 ms (50 × 50 subapertures) on the development board. For large wavefront sensors, the latency is dominated by access time (∼1 ms) of the standard DDR memory available on the board. This paper is divided into two parts. Part 1 is targeted at astronomers interested in the capability of the current hardware. Part 2 explains the FPGA implementation of the wavefront processing unit, the reconstruction algorithm and the hardware interfaces of the platform. Part 2 mainly targets the embedded developers interested in the hardware implementation of SPARC.

Proc. of the SPIE, 2014

We present wavefront reconstruction acceleration of high-order AO systems using an Intel Xeon Phi processor. The Xeon Phi is a coprocessor providing many integrated cores and designed for accelerating compute intensive, numerical codes. Unlike other accelerator technologies, it allows virtually unchanged C/C++ to be recompiled to run on the Xeon Phi, giving the potential of making development, upgrade and maintenance faster and less complex. We benchmark the Xeon Phi in the context of AO real-time control by running a matrix vector multiply (MVM) algorithm. We investigate variability in execution time and demonstrate an substantial speed-up in loop frequency. We examine the integration of a Xeon Phi into an existing RTC system and show that performance improvements can be achieved with limited development effort.

2003

Over the past two years ESO has reinforced its efforts in the field of Adaptive Optics. The AO team has currently the challenging objectives to provide 8 Adaptive Optics systems for the VLT in the coming years and has now a world-leading role in that field. This paper will review all AO projects and plans. We will present an overview of the Nasmyth Adaptive Optics System (NAOS) with its infrared imager CONICA installed successfully at the VLT last year. Sodium Laser Guide Star plans will be introduced. The status of the 4 curvature AO systems (MACAO) developed for the VLT interferometer will be discussed. The status of the SINFONI AO module developed to feed the infrared integral field spectrograph (SPIFFI) will be presented. A short description of the Multi-conjugate Adaptive optics Demonstrator MAD and its instrumentation will be introduced. Finally, we will present the plans for the VLT second-generation AO systems and the researches performed in the frame of OWL.

2016

The Large Synoptic Survey Telescope (LSST) is an 8-meter class wide-field telescope now under construction on Cerro Pachón, near La Serena, Chile. This ground-based telescope is designed to conduct a decade-long time domain survey of the optical sky. In order to achieve the LSST scientific goals, the telescope requires delivering seeing limited image quality over the 3.5 degree field of view. Like many telescopes, LSST will use an Active Optics System (AOS) to correct in near real-time the system aberrations primarily introduced by gravity and temperature gradients. The LSST AOS uses a combination of 4 curvature wavefront sensors (CWS) located on the outside of the LSST field-of-view. The information coming from the 4 CWS is combined to calculate the appropriate corrections to be sent to the 3 different mirrors composing LSST. The AOS software incorporates a wavefront sensor estimation pipeline (WEP) and an active optics control system (AOCS). The WEP estimates the wavefront residua...

1994

lbis paper outlines the key results of the Very Large Telescope (VLT) Adaptive Optics System Study perfonned by MMS/UTOS under an ESO contract A conceptual design was developed based entirely on available and demonstrated technologies. Key subsystems included a 250 actuator continuous facesheet Defonnable Mirror, an intensified Shack-Hartmann wavefront sensor and a DSP-based fast processor utilizing a parallel architecture. The

The next generation of Extremely Large Telescopes (ELTs) for astronomy will rely heavily on the performance of their adaptive optics (AO) systems. Real-time control is at the heart of the critical technologies that will enable telescopes to deliver the best possible science and will require a very significant extrapolation from current AO hardware existing for 4–10 m telescopes. Investigating novel real-time computing architectures and testing their eligibility against anticipated challenges is one of the main priorities of technology development for the ELTs. This paper investigates the suitability of the Intel Xeon Phi, which is a commercial off-the-shelf hardware accelerator. We focus on wavefront reconstruction performance, implementing a straightforward matrix–vector multiplication (MVM) algorithm. We present benchmarking results of the Xeon Phi on a real-time Linux platform, both as a standalone processor and integrated into an existing real-time controller (RTC). Performance of single and multiple Xeon Phis are investigated. We show that this technology has the potential of greatly reducing the mean latency and variations in execution time (jitter) of large AO systems. We present both a detailed performance analysis of the Xeon Phi for a typical E-ELT first-light instrument along with a more general approach that enables us to extend to any AO system size. We show that systematic and detailed performance analysis is an essential part of testing novel real-time control hardware to guarantee optimal science results.

IEEE Transactions on Industrial Informatics, 2018

An Adaptive Optics (AO) system is composed of three key elements: a wave-front sensor that detects the aberrations; a deformable mirror that provides the wavefront correction and a closed-loop control system that elaborates the measurements acquired by the sensor and sends commands to the mirror. The control system can be implemented on a dedicated platform (e.g. FPGA) or on general-purpose platforms (e.g. CPU, GPU). Dedicated hardware guarantees high performance but needs more development time and programming skills than general-purpose hardware, leading to a less maintainable system for the end user. The proposed solution aims to be a costeffective, multi-platform, CPU-based flexible framework. The software, developed in C++ and using Eigen and Qt libraries, provides the tools to tune and control the adaptive optics system, from wavefront measurement settings to controller parameters. A logging feature allows in-depth offline data analysis, while scripting enables execution of batch experiments. The adaptive optics system is tuned and evaluated by interfacing the wavefront sensor and deformable mirror with our software architecture. The results show that the proposed solution is able to correct the aberrations of a low to medium size SCAO system, with a control frequency up to 500Hz and computational latency of 40µs, using a consumer-grade notebook.

Ground-based and Airborne Telescopes VI, 2016

The Large Synoptic Survey Telescope (LSST) is an 8-meter class wide-field telescope now under construction on Cerro Pachón, near La Serena, Chile. This ground-based telescope is designed to conduct a decade-long time domain survey of the optical sky. In order to achieve the LSST scientific goals, the telescope requires delivering seeing limited image quality over the 3.5 degree field of view. Like many telescopes, LSST will use an Active Optics System (AOS) to correct in near real-time the system aberrations primarily introduced by gravity and temperature gradients. The LSST AOS uses a combination of 4 curvature wavefront sensors (CWS) located on the outside of the LSST field-of-view. The information coming from the 4 CWS is combined to calculate the appropriate corrections to be sent to the 3 different mirrors composing LSST. The AOS software incorporates a wavefront sensor estimation pipeline (WEP) and an active optics control system (AOCS). The WEP estimates the wavefront residual error from the CWS images. The AOCS determines the correction to be sent to the different degrees of freedom every 30 seconds. In this paper, we describe the design and implementation of the AOS. More particularly, we will focus on the software architecture as well as the AOS interactions with the various subsystems within LSST.

2018

The New Adaptive Optics Module for Interferometry (NAOMI) is ready to be installed at the 1.8-metre Auxiliary Telescopes (ATs) at ESO Paranal. NAOMI will make the existing interferometer performance less dependent on the seeing conditions. Fed with higher and more stable Strehl, the fringe tracker will achieve the fringe stability necessary to reach the full performance of the second-generation instruments GRAVITY and MATISSE. All four ATs will be equipped between September and November 2018 with a Deformable mirror (ALPAO DM-241), a 4*4 Shack– Hartmann adaptive optics system operating in the visible and an RTC based on SPARTA Light. During the last 6 months thorough system test has been made in laboratory to demonstrate the Adaptive Optics and chopping capability of NAOMI.

International Journal of Computer Mathematics, 2009

This work is carried out within a research collaboration with the Astronomical Observatory of Arcetri (Florence, Italy) aimed at the development of a parallel version of the adaptive optics simulation software named CAOS (Code for Adaptive Optics System). CAOS is currently used at the Arcetri Observatory to simulate the behaviour of an adaptive optic system, from the atmospheric turbulence corruption to the subsequent adaptive correction made on the wavefronts coming from the astronomical objects onto the pupils of the ground-based telescopes. We describe the computational efforts towards the integration of the CAOS package into a high-performance computing architecture, implementing three different parallelization approaches of a fast fourier transform (FFT)-based CAOS module and discuss the performance using standard performance metrics.

SPIE Proceedings, 2010

The next generation adaptive optics systems for large telescopes will be complex systems far larger, more complex, and with higher performance than any currently installed. This requires adopting new algorithms, technologies, and architectures. The Keck next generation adaptive optics (NGAO) system requires real-time wavefront reconstruction and tomography given input from 7 laser and 3 natural guide stars. Requirements include 2 KHz atmospheric sampling, tomographic atmosphere estimation, and control for 5 deformable mirrors. We take advantage of the algorithms' massive parallelism and realize it on a massive array of FPGAs, GPUs, and multi-core CPUs. This paper presents the current design and analysis of the NGAO system.

SPIE Proceedings, 2003

Adaptive optics (AO) systems currently under investigation will require at least two orders of magitude increase in the number of actuators, which in turn translates to effectively a 10 4 increase in compute latency. Since the performance of an AO system invariably improves as the compute latency decreases, it is important to study how today's computer systems will scale to address this expected increase in actuator utilization. This paper answers this question by characterizing the performance of a single deformable mirror (DM) Shack-Hartmann natural guide star AO system implemented on the present-generation digital signal processor (DSP) TMS320C6701 from Texas Instruments. We derive the compute latency of such a system in terms of a few basic parameters, such as the number of DM actuators, the number of data channels used to read out the camera pixels, the number of DSPs, the available memory bandwidth, as well as the inter-processor communication (IPC) bandwidth and the pixel transfer rate. We show how the results would scale for future systems that utilizes multiple DMs and guide stars. We demonstrate that the principal performance bottleneck of such a system is the available memory bandwidth of the processors and to lesser extent the IPC bandwidth. This paper concludes with suggestions for mitigating this bottleneck.

Adaptive Optics Systems VIII

MAVIS will be part of the next generation of VLT instrumentation and it will include a visible imager and a spectrograph, both fed by a common Adaptive Optics Module. The AOM consists in a MCAO system, whose challenge is to provide a 30" AO-corrected FoV in the visible domain, with good performance in a 50% sky coverage at the Galactic Pole. To reach the required performance, the current AOM scheme includes the use of up to 11 reference sources at the same time (8 LGSs + 3 NGSs) to drive more than 5000 actuators, divided into 3 deformable mirrors (one of them being UT4 secondary mirror). The system also includes some auxiliary loops, that are meant to compensate for internal instabilities (including WFSs focus signal, LGS tip-tilt signal and pupil position) so to push the stability of the main AO loop and the overall performance. Here we present the Preliminary Design of the AOM, which evolved, since the previous phase, as the result of further trade-offs and optimizations. We also introduce the main calibration strategy for the loops and subsystems , including NCPA calibration approach. Finally, we present a summary of the main results of the performance and stability analyses performed for the current design phase, in order to show compliance to the performance requirements.

2003

MACAO stands for Multi Application Curvature Adaptive Optics. A similar concept is applied to fulfill the need for wavefront correction for several VLT instruments. MACAO-VLTI is one of these built in 4 copies in order to equip the Coude focii of the ESO VLT's. The optical beams will then be corrected before interferometric recombination in the VLTI (Very Large Telescope Interferometer) laboratory. MACAO-VLTI uses a 60 elements bimorph mirror and curvature wavefront sensor. A custom made board processes the signals provided by the wavefront detectors, 60 Avalanche Photo-diodes, and transfer them to a commercial Power PC CPU board for Real Time Calculation. Mirrors Commands are sent to a High Voltage amplifier unit through an optical fiber link. The tip-tilt correction is done by a dedicated Tip-tilt mount holding the deformable mirror. The whole wavefront is located at the Coude focus. Software is developed in house and is ESO compatible. Expected performance is a Strehl ratio sligthly under 60% at 2.2 micron for bright reference sources (star V<10) and a limiting magnitude of 17.5 (Strehl ~0.1). The four systems will be installed in Paranal successively, the first one being planned