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International audience; HARMONI is the first light, adaptive optics assisted, integral field spectrograph for the European Southern Observatory’s Extremely Large Telescope (ELT). A work-horse instrument, it provides the ELT’s diffraction limited spectroscopic capability across the near-infrared wavelength range. HARMONI will exploit the ELT’s unique combination of exquisite spatial resolution and enormous collecting area, enabling transformational science. The design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument’s capabilities from a user perspective, and provide a summary of the instrument’s design. We also include recent changes to the project, both technical and programmatic, that have resulted from red-flag actions. Finally, we outline some of the simulated HARMONI observations currently being analyzed.

International audience

HARMONI is the adaptive optics assisted, near-infrared and visible light integral field spectrograph for the Extremely Large Telescope (ELT). A first light instrument, it provides the work-horse spectroscopic capability for the ELT. As the project approaches its Final Design Review milestone, the design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument's capabilities from a user perspective, provide a summary of the instrument's design, including plans for operations and calibrations, and provide a brief glimpse of the predicted performance for a specific observing scenario. The paper also provides some details of the consortium composition and its evolution since the project commenced in 2015.

The WEB (Wind Evaluation Breadboard) for the European ELT (Extremely Large Telescope) Design Study is a primary mirror and telescope simulator formed by seven segments, including position sensors, electromechanical support systems and support structures. The purpose of the WEB is to study the effects of wind on the control of the positions of the segments. This paper describes the control architecture, the dynamic model generated based on the Finite Element Model and the performances achieved in simulations.

The Wind Evaluation Breadboard (WEB) is a primary mirror and telescope simulator formed by seven aluminium segments, including position sensors, electromechanical support systems and support structures. WEB has been developed to evaluate technologies for primary mirror wavefront control and to evaluate the performance of the control of wind buffeting disturbance on ELT segmented mirrors. For this purpose WEB electro-mechanical set-up simulates the real operational constrains applied to large segmented mirrors. This paper describes the WEB assembly, integration and verification, the instrument characterisation and close loop control design, including the dynamical characterization of the instrument and the control architecture. The performance of the new technologies developed for position sensing, acting and controlling is evaluated. The integration of the instrument in the observatory and the results of the first experiments are summarised, with different wind conditions, elevation and azimuth angles of incidence. Conclusions are extracted with respect the wind rejection performance and the control strategy for an ELT. WEB has been designed and developed by IAC, ESO, ALTRAN and JUPASA, with the integration of subsystems of FOGALE and TNO.

European Extremely Large Telescope (E-ELT) based in 984 primary mirror segments achieving required optical performance; they must position relatively to adjacent segments with relative nanometer accuracy. CESA designed M1 Position Actuators (PACT) to comply with demanding performance requirements of EELT. Three PACT are located under each segment controlling three out of the plane degrees of freedom (tip, tilt, piston). To achieve a high linear accuracy in long operational displacements, PACT uses two stages in series. First stage based on Voice Coil Actuator (VCA) to achieve high accuracies in very short travel ranges, while second stage based on Brushless DC Motor (BLDC) provides large stroke ranges and allows positioning the first stage closer to the demanded position. A BLDC motor is used achieving a continuous smoothly movement compared to sudden jumps of a stepper. A gear box attached to the motor allows a high reduction of power consumption and provides a great challenge for sizing. PACT space envelope was reduced by means of two flat springs fixed to VCA. Its main characteristic is a low linear axial stiffness. To achieve best performance for PACT, sensors have been included in both stages. A rotary encoder is included in BLDC stage to close position/velocity control loop. An incremental optical encoder measures PACT travel range with relative nanometer accuracy and used to close the position loop of the whole actuator movement. For this purpose, four different optical sensors with different gratings will be evaluated. Control strategy show different internal closed loops that work together to achieve required performance.

The Wind Evaluation Breadboard (WEB) for the European Extremely Large Telescope (ELT) is a primary mirror and telescope simulator formed by seven segments simulators, including position sensors, electromechanical support systems and support structures. The purpose of the WEB is to evaluate the performance of the control of wind buffeting disturbance on ELT segmented mirrors using an electro-mechanical set-up which simulates the real operational constrains applied to large segmented mirrors. The instrument has been designed and developed by IAC, ALTRAN, JUPASA and ESO, with FOGALE responsible of the Edge Sensors, and TNO of the Position Actuators. This paper describes the mechanical design and analysis, the control architecture, the dynamic model generated based on the Finite Element Model and the close loop performance achieved in simulations. A comparison in control performance between segments modal control and actuators local control is also presented.

We present EDiFiSE, a prototype instrument for the observation of high-contrast systems, combining an adaptive optics (AO) system and an equalized integral field unit (EIFU). The design of the AO system takes into account the statistical behaviour of the atmospheric turbulence structure at the Canary Islands (Spain) astronomical observatories: Roque de los Muchachos (ORM) on the island of La Palma and Teide observatory (OT) in Tenerife. The AO will have the capability of adapting to the prevailing turbulence conditions; in this sense, the EDiFiSE AO unit will be an 'adaptable' adaptive optics system. The corrected beam feeds an hexagonal integral field unit formed by 331 micro-lenslets, which focus the intensity distribution at the focal plane into 331 optical fibers. The central seven fibers of the bundle include variable attenuators for the equalization of these fibers output intensities, matching them to the dynamical range of the detector and reducing the optical cross talk inside the spectrograph. This technique, called equalized integral field spectroscopy (Arribas, Mediavilla & Fuensalida 19981), permits to obtain spectral and spatial information of the equalized object and its surroundings as well as accurate relative photometry and astrometry.

Adaptive optics is a very promising field in earth-based astronomy, and has become a must in the development of large (10 m) and giant (50-100 m) telescopes. Real time compensation of the atmospheric turbulence requires a huge amount of processing power that goes beyond the practical limits of today's processor capability, and perhaps tomorrow's. FPGAs may become a viable approach when exploiting their natural parallel arrangement and their continuously improving speed, after their size has grown up to the point of accepting a whole system to be embedded in just one unit. In order to evaluate the feasibility of such a system, a laboratory adaptive optical test bench has been developed, needing only one VTRTEX-4 FPGA to implement the whole closed loop processing chain, computing 39 actuations from a 8times8 microlenses array at 1000 images per second.

FPGA (Field Programmable Gate Array) technology has become a very powerful tool available to the electronic designer, specially after the spreading of high quality synthesis and simulation software packages at very affordable prices. They also offer high physical integration levels and high speed, and eases the implementation of parallelism to obtain superb features. Adaptive optics for the next generation telescopes (50-100 m diameter) -or improved versions for existing ones- requires a huge amount of processing power that goes beyond the practical limits of today's processor capability, and perhaps tomorrow's, so FPGAs may become a viable approach. In order to evaluate the feasibility of such a system, a laboratory adaptive optical test bench has been developed, using only FPGAs in its closed loop processing chain. A Shack-Hartmann wavefront sensor has been implemented using a 955-image per second DALSA CA-D6 camera, and a 37-channel OKO mirror has been used for wavefront correcting. Results are presented and extrapolation of the behavior for large and extremely large telescopes is discussed.

In the frame of the SILEX project, the European Space Agency (ESA) has put into orbit two Laser Communication Terminals, to establish an experimental free space optical communication link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV), to relay earth observation data. In order to perform In Orbit Testing (IOT) of these, and other, optical communications systems, ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for building the Optical Ground Station (OGS), in the Teide Observatory of the IAC. With ARTEMIS placed in a circular parking orbit at about 31000 kilometres, its optical payload has been preliminary tested with the OGS. First results and analysis are presented on the space-to-ground bi-directional link, including pointing acquisition and tracking performance, Bit-Error Rate (BER) and transmitted beam divergence effects related with atmospheric models and predictions. Future plans include deeper optical bi-directional communication tests of OGS, not only with ARTEMIS but also with OSCAR-40 (downlink) and SMART-1 (up-link) satellites, in order to do a full characterisation of the performances of laser beam propagation through atmospheric turbulence and a comparison with theoretical predictions.

The European Space Agency (ESA) has undertaken the development of Optical Data Relay payloads, aimed at establishing free space optical communication links between satellites. The first of such systems put into orbit is the SILEX project, in which an experimental link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV) will be used to relay earth observation data. In order to perform In Orbit Testing (IOT) of these and future optical communications systems, ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for the building of the Optical Ground Station (OGS) in the IAC Teide Observatory, which consists basically of a 1-meter telescope and the suitable instrumentation for establishing and testing bi-directional optical links with satellites. The presence of the atmosphere in the data path posses particular problems, with an impact on the instrumentation design. The transmission, reception and measurement functions, along with the overall control of the instruments, are performed at OGS by the Focal Plane Control Electronics (FPCE). The design and performance of this instrumentation is presented, emphasizing the Pointing, Acquisition and Tracking, the Tuneable Laser and the Master Control.

ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreemenet for building the Optical Ground Station (OGS), in the IAC Teide Observatory, in order to perform In Orbit Testing (IOT) of Optical Data Relay payloads onboard communication satellites, the first being ARTEMIS. During its recent launch, ARTEMIS was put into a degraded orbit due to a malfunction on the launcher's upper stage. ESA rapidly adopted a recovery strategy aimed to take the satellite to its nominal geostationary position. After completion of the first manoeuvres, ARTEMIS was successfully positioned in a circular parking orbit, at about 31,000 kilometers, and turned into full operation. In this orbit, its optical payload has been tested with the OGS, before establishing the link with SPOT IV. New tracking algorithms were developed at OGS control system in order to correct for ARTEMIS new orbit. The OGS has established a bi-directional link to ARTEMIS, behaving, seen from ARTEMIS, as a LEO terminal. Preliminary results are presented on the space-to- ground bi-directional link, including pointing acquisition and tracking (PAT) performance, received beam characterization and BER measurements.