The construction of a diffraction limitable telescope as large as the ESO’s ELT is enabled by its embedded deformable quaternary mirror. Besides its essential function in the telescope control, M4 also contributes to compensating the free atmosphere aberrations for all post-focal AO applications. The paper presents how the telescope manages M4 to maintain its optical performance while offering to the instruments a clean wavefront interface, supporting the desired AO functionalities. The paper reviews the telescope strategy to derive its wavefront dynamic properties directly from the analysis of the control data collected in science mode, with the goal to minimize the observatory time spent on dedicated wavefront calibration tasks.
We present an optomechanical test bench setup (MELT) for testing and validating key functionalities to be used on the Extremely Large Telescope (ELT) during the periods of system verification, wavefront control commissioning, through the handover to science, up to regular diagnostic, monitoring, and validation tasks during operations.
The main objectives of MELT are to deploy and validate the telescope control system, to deploy and validate wavefront control algorithms for commissioning and operations, as well as to produce and validate key requirements for the phasing and diagnostic station (PDS) of the ELT.
The purpose of MELT is to deploy optomechanical key components such as a segmented primary mirror, a secondary mirror on a hexapod, an adaptive fourth mirror, and a fast tip/tilt mirror together with their control interfaces that emulate the real telescope optomechanical conditions. The telescope control system, deployed on MELT can test control schemes with the active mounts emulating the real ELT optomechanical control interfaces.
The presented optomechanical setup uses the Active Segmented Mirror (ASM) with its piezo-driven 61 segments and a diameter of 15 cm. It was designed, built, and used on sky during the Active Phasing Experiment (APE).
Several beam paths after the telescope optical train on MELT are conditioned and guided to wavefront sensors and cameras, sensitive to wavelength bands in the visible and infrared to emulate wavefront commissioning and phasing tasks. This optical path resembles part of the phasing and diagnostics station (PDS) of the ELT, which is used to acquire the first star photons through the ELT and to learn the usage and control of all the ELT optomechanics. The PDS will be developed, designed, and built in-house at ESO. MELT helps its design by providing a detailed test setup for defining and deploying system engineering tasks, such as detailed functional analysis, definition of tasks to be carried out, and technical requirements, as well as operational commissioning aspects.
The bench test facility MELT will in the end help us to be as much as possible prepared when the telescope sends the first star light through the optical train to be able to tackle the unforeseeable problems and not be caught up with the foreseeable ones.
The European Extremely Large Telescope is a project of the European Southern Observatory to build and operate a 40-m
class optical near-infrared telescope. The telescope design effort is largely concluded and construction contracts are
being placed with industry and academic/research institutes for the various components. The siting of the telescope in
Northern Chile close to the Paranal site allows for an integrated operation of the facility providing significant economies.
The progress of the project in various areas is presented in this paper and references to other papers at this SPIE meeting
During the last year a modified baseline design for the E-ELT has been developed. The aim of this revision was both to
achieve a significant cost saving and to reduce risk on major items. The primary mirror diameter was slightly reduced to
39 m and the total height of the telescope also decreased accordingly. This paper describes the work performed by ESO
and a variety of contractors to review the EELT design to match the modified baseline. Detailed design and construction
planning, as well as detailed cost estimates were updated for the 39-metre baseline design. In June 2011, ESO Council
formally endorsed this modified design as the E-ELT revised baseline.
The design drivers and balancing cost factors will be described along with the risk reduction measures taken during this
phase. This will culminate in the design which has been agreed as being ready to move forward to construction once
approval from ESO Council has been achieved.
The Rapid-Response Mode (RRM) at ESO's Very Large Telescope (VLT) allows for rapid automatic observations
of any highly variable target such as Gamma-Ray Burst (GRB) afterglows. This mode has been available
for various instruments at the VLT since April 2004, and can be easily implemented for any new instumentation.
Apart from discussing the operational side of this mode, we also present VLT/UVES GRB afterglow spectra
observed using the RRM, which show clear variability of absorption lines at the redshift the GRB host galaxy.
Without the RRM this variability would not have been observed. Using photo-excitation and -ionization modelling,
we show that this varibility is due to the afterglow flux exciting and ionizing a gas cloud at distances
varying from tens of parsecs to kiloparsecs away from the GRB.
The EELT is a project led by ESO on behalf of its 14 member states. The project is in Phase B (detailed design), a
3-year, 57.2 M activity that will result in a Proposal for Construction by June 2010. The requirements for the basic
reference design, starting point for the current phase, were defined through a community process that led to the
convergence of earlier concepts into a single European project: a 42m adaptive telescope based on a novel 5-mirror
design that is scheduled to have first light in 2017. This paper reports on the status of the Phase B activities, on the basic
reference design development, and on the progress of the science case and Design Reference Mission.
The European Extremely Large telescope project is in phase B and scheduled to present a construction proposal to the
ESO Council by the end of 2009 or early 2010. The telescope baseline is for a fully steerable 42-m, segmented primary,
5 mirror design, fully adaptive system with Nasmyth and coude foci. This paper describes the current state of affairs with
the European ELT and, in view of this conference celebrating Arne Ardeberg's contributions to astronomy, contains the
occasional, totally incomplete, retrospective to earlier work in the field focusing on a single paper by Ardeberg et al in
The ESO Very Large Telescope Interferometer (VLTI) is the first general-user interferometer that offers near- and mid-infrared long-baseline interferometric observations in service and visitor mode to the whole astronomical community. Over the last two years, the VLTI has moved into its regular science operation mode with the two science instruments, MIDI and AMBER, both on all four 8m Unit Telescopes and the first three 1.8m Auxiliary Telescopes. We are currently devoting up to half of the available time for science, the rest is used for characterization and improvement of the existing system, plus additional installations. Since the first fringes with the VLTI on a star were obtained on March 17, 2001, there have been five years of scientific observations, with the different instruments, different telescopes and baselines. These observations have led so far to more than 40 refereed publications. We describe the current status of the VLTI and give an outlook for its near future.
APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the world's outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 μm makes APEX suitable for observations up to 200 μm, through all atmospheric submm windows accessible from the ground.
MIDI (MID-infrared Interferometric instrument) gave its first N-band (8 to 13 micron) stellar interference fringes on the VLTI (Very Large Telescope Interferometer) at Cerro Paranal Observatory (Chile) in December 2002. An lot of work had to be done to transform it, from a successful physics experiment, into a premium science instrument which is offered to the worldwide community of astronomers since September 2003. The process of "paranalization", carried out by the European Southern Observatory (ESO) in collaboration with the MIDI consortium, has aimed to make MIDI simpler to use, more reliable, and more efficient. We describe in this paper these different aspects of paranalization (detailing the improvement brought to the observation software) and the lessons we have learnt. Some general rules, for bringing an interferometric instrument into routine operation in an observatory, can be drawn from the experience with MIDI. We also report our experience of the first "service mode" run of an interferometer (VLTI + MIDI) that took place in April 2004.
Progress in the conceptual design phase of ESO's OWL 100-m optical and near-infrared telescope is reported, with emphasis on the development of the science case. The Phase A opto-mechanical design is now basically completed, and provides a clean, symmetrical geometry of the pupil, with a near-circular outer edge. We also report about the latest outcome of industrial studies, introduce the essential definition of the wavefront control systems, and outline operational concepts and instruments priorities. Finally, we elaborate on the favorable cost factors associated to the telescope design, its compatibility with low industrial risks, and argue that progressive implementation allows for competitive timescales. In particular, we show that suitable fabrication and integration schemes should accommodate for a start of science operation at unequalled potential and within a time frame comparable to that of smaller designs, while at the same time maximizing R&D time for critical subsystems.
The first of the Unit telescopes of the VLT has now been in operation for 5 years. The complete array has been producing scientific results since 2001 and the VLTI has in the past few months celebrated common user status with MIDI on the Unit telescopes. With the first of four auxiliary telescope already on site and VST and VISTA in construction, Paranal observatory is rapidly reaching maturity. Combining the power of these facilities with service observing and full user support the VLT is already having a significant impact on astronomy. In this paper we review our operations and present some metrics of what we believe is success.
In November 2001, the VLT has been equipped for the first time with an adaptive optics system, NAOS. NAOS has been designed to provide good image quality over a wide range of conditions, allowing thus a large variety of astrophysical programs, from Solar System to extragalactic studies. NAOS feeds a camera CONICA which provides imaging, coronagraphic, spectroscopic and polarimetric capabilities between 1 and 5 microns. NAOS and CONICA (hereafter NACO) have been commissioned over the past months. We present in this paper the first images recorded by NACO during the commissioning period, illustrating the capabilities of this new instrument.
On March 17, 2001, the VLT interferometer saw for the first time interferometric fringes on sky with its two test siderostats on a 16m baseline. Seven months later, on October 29, 2001, fringes were found with two of the four 8.2m Unit Telescopes (UTs), named Antu and Melipal, spanning a baseline of 102m. First shared risk science operations with VLTI will start in October 2002. The time between these milestones is used for further integration as well as for commissioning of the interferometer with the goal to understand all its characteristics and to optimize performance and observing procedures. In this article we will describe the various commissioning tasks carried out and present some results of our work.
Telescopes are built to do astronomy. Often this point is taken to extremes by astronomers demanding access to facilities before they are ready to receive them and often engineers dwell on aspects of a system that have little impact on the final performance of the machine. The right balance may never be found. Doing science early may scoop the competition but doing science more often may be the best long term investment. A systematic approach to commissioning has been adopted at ESO within the VLT project with the end operability and maintainability being a major driver of the activities. In this paper are presented the historical, strategic and problematic aspects of the commissioning of the VLT.
The VLT is a complete new observatory situated at cerro Paranal in the north Atacama desert of Chile. The four 8.2-m telescopes of the VLT are in continuous science operations and are operating with very high efficiency. The operational scenario allows users the options for service or visitor mode observing providing great flexibility to the European astronomical community to fully exploit the telescopes. The interferometric mode of the VLT is already producing scientific results and has demonstrated excellent stability and operability.
After the installation of the four Unit Telescopes of the VLT in the years 1998 till 2000 more than 1.5 million active optics measurements and corrections have been performed. Since all active optics data are logged together with various environmental parameters (external seeing, temperatures, wind, etc.) extensive statistical studies of the dependence of the optical performance of the telescope on the external parameters can be made. Improvements of the functionality and the performance of the telescopes include the use of a Kalman filter in the Active Optics correction loop and the possibility to adjust actively the plate scale of the telescope.
Preliminary requirements and possible technological solutions for the next generation of ground-based optical telescopes were laid down at ESO in 1998. Since then, a phase A study has been commissioned, the objective of which is to produce a conceptual design compatible, to the maximum possible extent, with proven technology, and establish realistic plans for detailed design, site selection, construction and operation for a 100-m class optical, diffraction-limited telescope. There was no doubt about how daunting such a challenge would be, but, somewhat surprisingly, it turns out to be firmly confined to adaptive optics concepts and technologies. The telescope itself appears to be feasible within the allocated budget and without reliance on exotic assumptions. Fabrication of key subsystems is fully within the reach of a properly engineered, industrialized process. A consolidated baseline is taking shape, and alternative system and subsystem solutions are being explored, strengthening the confidence that requirements could be met. Extensive development of wavefront measurement techniques enlarges the palette of solutions available for active wavefront control of a segmented, active telescope. At system level, ESO is developing enabling experiments to validate multi-conjugate adaptive optics (MAD for Multi-conjugate Adaptive optics Demonstrator) and telescope wavefront control (APE, for Active Phasing Experiment).
FORS is an all dioptric focal reducer designed for direct imaging, low-dispersion multi-object spectroscopy, imaging polarimetry and spectropolarimetry of faint objects. Two almost identical copies of the instrument were built by a consortium of three astronomical institutes under contract and in cooperation with ESO. FORS1 was installed in September 1998 and FORS2 in October 1999 at the Cassegrain foci of the ESO VLT unit telescope nos. 1 and 2. FORS1 is in regular operation since April 1999. Regular observation with FORS2 are scheduled to begin in April 2000.
The first VLT unit telescope, Antu, saw first light in May 1998 and started science operation in April 1999, roughly at the same time as first light of unit telescope 2, Kueyen, was achieved. The time between first light and science operation is used to verify, quantify, qualify and optimize the functionality and performance of the telescopes and their instruments.
During the design phase of the ESO Very Large Telescope considerably emphasis was placed on providing the means of controlling and monitoring thermal and wind disturbances. Today, about one year after the start of operation of the first Unit Telescope, much has been learned about the behavior of the telescope, and also about the optimum control strategies to reduce such disturbances. This paper outlines the current strategy for the control of environmental disturbances and discuses some of the lessons that have been learned.
The active optics system of the ESO Very Large Telescope has now been in operation since May 1998. All results from the wavefront analyses as well as numerous other telescope and environmental data are continuously logged. This allows for an accurate assessment of the performance of the active optics system and yields statistical correlations between the wavefront data and other telescope or external parameters.
Science operations at the ESO very large telescope is scheduled to begin in April 1999. ESO is currently finalizing the VLT science operations plan. This plan describes the operations tasks and staffing needed to support both visitor and service mode operations. The Data Flow Systems (DFS) currently being developed by ESO will provide the infrastructure necessary for VLT science operations. This paper describes the current VLT science operations plan, first by discussing the tasks involved and then by describing the operations teams that have responsibility for those tasks. Prototypes of many of these operational concepts and tools have been in use at the ESO New Technology Telescope (NTT) since February 1997. This paper briefly summarizes the status of these prototypes and then discusses what operation lessons have been learned from the NTT experience and how they can be applied to the VLT.
The NTT project had the principal aim of field testing the VLT control system prior to installation on UT1 on Paranal. In July 1996 we began installing the control electronics and software. The telescope was stripped down to the field electronics and completely rewired. First light was achieved 2 months later and the integration of the system was completed 4 months after that. The VLT control system has been proven to be functional and fundamentally sound. Over 80% of the VLT control system is mirrored on the NTT with deviations only allowed where the hardware made it impossible to reuse the code prepared for Paranal. The NTT will operate with the complete control system executing service observations following the shake down period in early 1997.
Until recently the study of cool clouds of interstellar matter had been limited by the relatively low spectral resolutions provided by existing spectrographs. The Ultra-High-Resolution Facility (UHRF) recently commissioned at the Anglo-Australian Telescope has changed dramatically this panorama by delivering for the first time resolutions approaching one million, near the diffraction limit of the largest echelle gratings available. The instrument shares the east coude room with the University College London Echelle Spectrograph, in what is now one of the most powerful spectrographic installations worldwide. This contribution describes the characteristics of the UHRF, including its design, manufacture, testing, and commissioning. The UHRF incorporates a novel image slicer (described elsewhere in these proceedings), which allows ultra-high-resolution observations on faint objects. Astrophysical results from the first observing runs are presented to demonstrate the UHRF performance in both resolution and throughput.