Philippe Feautrier

MAORY is the ELT-MCAO system providing first-light wide-field correction for the near infrared imager and spectrograph MICADO. This paper provides an overview of the systems engineering processes and tools implemented to MAORY project during preliminary design phase and it illustrates, with some practical examples, the role of MAORY technical budgets to derive requirements on subsystems. One of the critical activities in systems engineering is the requirements managing. In line with this, the MAORY team devotes a significant effort to this activity, which follows a well-established process. This involves the MAORY requirements break-down to subsystems level and from here down to subsystems procurements specifications. This paper also presents an overview of the MAORY Technical Budgets. One task of the System Engineering is to manage the technical budgets at system level combining the contributors at subsystems level to meet the overall requirements.

In this paper we present the structure, organization and risk management of the MAORY Consortium, an Italian-French collaboration for the design and construction of the adaptive optics module for the European Large Telescope.

For the first time, subelectron readout noise has been achieved with a camera dedicated to astronomical wavefront-sensing applications. The OCam system demonstrated this performance at a 1300 Hz frame rate and with 240 × 240 pixel frame size. ESO and JRA2 OPTICON jointly funded e2v Technologies to develop a custom CCD for adaptive optics (AO) wavefront-sensing applications. The device, called CCD220, is a compact Peltier-cooled 240 × 240 pixel frame-transfer eight-output back-illuminated sensor using the EMCCD technology. This article demonstrates, for the first time, subelectron readout noise at frame rates from 25 Hz to 1300 Hz and dark current lower than 0.01 e^- pixel^-1 frame^-1. It reports on the quantitative performance characterization of OCam and the CCD220, including readout noise, dark current, multiplication gain, quantum efficiency, and charge transfer efficiency. OCam includes a low-noise preamplifier stage, a digital board to generate the clocks, and a microcontroller. The data acquisition system includes a user-friendly timer file editor to generate any type of clocking scheme. A second version of OCam, called OCam², has been designed to offer enhanced performance, a completely sealed camera package, and an additional Peltier stage to facilitate operation on a telescope or environmentally challenging applications. New features of OCam² are presented in this article. This instrumental development will strongly impact the performance of the most advanced AO systems to come.

For the first time, sub-electron read noise has been achieved with a camera suitable for astronomical wavefront-sensing (WFS) applications. The OCam system has demonstrated this performance at 1300 Hz frame rate and with 240×240-pixel frame rate. ESO and JRA2 OPTICON² have jointly funded e2v technologies to develop a custom CCD for Adaptive Optics (AO) wavefront sensing applications. The device, called CCD220, is a compact Peltier-cooled 240×240 pixel frame-transfer 8-output back-illuminated sensor using the EMCCD technology. This paper demonstrates sub-electron read noise at frame rates from 25 Hz to 1300 Hz and dark current lower than 0.01 e-/pixel/frame. It reports on the comprehensive, quantitative performance characterization of OCam and the CCD220 such as readout noise, dark current, multiplication gain, quantum efficiency, charge transfer efficiency... OCam includes a low noise preamplifier stage, a digital board to generate the clocks and a microcontroller. The data acquisition system includes a user friendly timer file editor to generate any type of clocking scheme. A second version of OCam, called OCam², was designed offering enhanced performances, a completely sealed camera package and an additional Peltier stage to facilitate operation on a telescope or environmentally rugged applications. OCam² offers two types of built-in data link to the Real Time Computer: the CameraLink industry standard interface and various fiber link options like the sFPDP interface. OCam² includes also a modified mechanical design to ease the integration of microlens arrays for use of this camera in all types of wavefront sensing AO system. The front cover of OCam² can be customized to include a microlens exchange mechanism.

ESO and JRA2 OPTICON have funded e2v technologies to develop a compact packaged Peltier cooled 24 μm square 240x240 pixels split frame transfer 8-output back-illuminated L3Vision CCD3, L3Vision CCD for Adaptive Optic Wave Front Sensor (AO WFS) applications. The device is designed to achieve sub-electron read noise at frame rates from 25 Hz to 1,500 Hz and dark current lower than 0.01 e-/pixel/frame. The development has many unique features. To obtain high frame rates, multi-output EMCCD gain registers and metal buttressing of row clock lines are used. The baseline device is built in standard silicon. In addition, a split wafer run has enabled two speculative variants to be built; deep depletion silicon devices to improve red response and devices with an electronic shutter to extend use to Rayleigh and Pulsed Laser Guide Star applications. These are all firsts for L3Vision CCDs. The designs of the CCD and Peltier package have passed their reviews and fabrication has begun. This paper will describe the progress to date, the requirements and the design of the CCD and compact Peltier package, technology trade-offs, schedule and proposed test plan. High readout speed, low noise and compactness (requirement to fit in confined spaces) provide special challenges to ESO's AO variant of its NGC, New General detector Controller to drive this CCD. This paper will describe progress made on the design of the controller to meet these special needs.

In the past decade, new tools have been offered to the system designers in terms of thermal and mechanical modeling. In addition to an overwhelming increase of computer capabilities, these tools are now mature enough to drive the design of complex astronomical instruments, in particular if these instruments have to be cooled. This is the case of WIRCam, the new wide-field infrared camera to be installed on the CFHT in Hawaii on the Mauna Kea summit. This camera uses four 2Kx2K Rockwell Hawaii-2RG infrared detectors and includes 2 optical barrels and 2 filter wheels. This camera is mounted at the prime focus of the 3.6m CFHT telescope. The mass to be cooled is close to 100 kg. The camera will use a Gifford Mac-Mahon closed-cycle cryo-cooler in order to avoid strenuous daily re-fillings on the telescope due to the camera location. This paper will present the thermal-mechanical model of the camera using Finite-Element Analysis under the I-deas software. The capabilities of the I-deas thermal module (TMG) will be demonstrated for our particular application: including conduction, radiation and free-convection management, variations of the cooling power and thermal characteristics of the materials as a function of the temperature, and studies in permanent regime and transient analysis. The hypotheses used for the thermal model are explained and results of the model are shown to explain the choice of the cryo-cooler. Predicted performances (cooling down time, warm-up time, and mechanical deformations) are presented and compared to measurements. All these models were carried out using a normal PC laptop running I-deas/TMG.

The NAOS adaptive optics system was installed in December 2001 on the Nasmyth focus of the ESO VLT. It includes two wavefront sensors: one is working at IR wavelength analysis and the other at visible wavelengths. This paper describes the NAOS Visible Wave Front Sensor based on a Shack-Hartman principle and its performances as measured on the sky. This wavefront sensor includes within a continuous flow liquid nitrogen cryostat: 1) a low noise fast readout CCD camera controlled by the ESO new generation CCD system FIERA using a fast frame rate EEV/Marconi CCD-50 focal plane array. This 128×128 pixels focal plane array has a readout noise of 3 e- at 50 kilopixel/sec/port. FIERA provides remotely controlled readout modes with optional binning, windowing and flexible integration time. 2) two remotely exchangeable micro-lens arrays (14×14 and 7×7 micro-lenses) cooled at the CCD temperature ( -100 °C) within the cryostat. The CCD array is directly located in the micro lenses focal plane at a few millimeters apart without relay optics. 3) Additional opto-mechanical functions are also provided (atmospheric dispersion compensator, flux level control, field of view limitation). On sky performances of the wavefront sensor are presented. Adaptive Optics corrections was obtained with a reference star as faint as a visible magnitude 17 with a band-path of 40 Hz in close loop.