We present data collected using the camera PISCES coupled with the Firt Light Adaptive Optics (FLAO) mounted at the Large Binocular Telescope (LBT). The images were collected for two different pointings by using two natural guide stars with an apparent magnitude of R ~< 13 mag. During these observations the seeing was on average ~0.9 arcsec. The AO performed very well, in fact the images display a mean FWHM of 0.05 arcsec and of 0.06 arcsec in the J– and in the Ks–band, respectively. The Strehl ratio on the quoted images reaches 13–30% (J) and 50–65% (Ks), in the off and in the central pointings respectively. On the basis of this sample we have reached a J–band limiting magnitude of ~22.5 mag and the deepest Ks–band limiting magnitude ever obtained in a crowded stellar field: Ks ~23 mag. J–band images display a complex change in the shape of the PSF when moving at larger radial distances from the natural guide star. In particular, the stellar images become more elongated in approaching the corners of the J-band images whereas the Ks–band images are more uniform. We discuss in detail the strategy used to perform accurate and deep photometry in these very challenging images. In particular we will focus our attention on the use of an updated version of ROMAFOT based on asymmetric and analytical Point Spread Functions. The quality of the photometry allowed us to properly identify a feature that clearly shows up in NIR bands: the main sequence knee (MSK). The MSK is independent of the evolutionary age, therefore the difference in magnitude with the canonical clock to constrain the cluster age, the main sequence turn off (MSTO), provides an estimate of the absolute age of the cluster. The key advantage of this new approach is that the error decreases by a factor of two when compared with the classical one. Combining ground–based Ks with space F606W photometry, we estimate the absolute age of M15 to be 13.70± 0.80 Gyr.
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 EELT project is in Phase B (detailed design), a 3-year, 57.2 Mσ activity that will result in a Proposal for
Construction by end 2009 or early 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. That process owed much to Arne's wisdom and vision. This paper reports on the status of the Phase B and on the
development of the EELT science case and Design Reference Mission, and examines the issue of the impact of the
telescope size on science and how much this impact depends on Adaptive Optics technology. The design of the telescope
is described in a separate paper in these proceedings.
The science case for the next generation of Extremely Large Telescopes (ELTs) covers a huge range of astronomical
topics and requires a wide range of capabilities. Here we describe top-level requirements on an ELT, which were derived
from some of the key science cases identified by European astronomers. After a brief summary of these science cases we
discuss the requirements on the ELT system in terms of several parameters, including wavelength range, field of view,
image quality etc. We discuss the science driver that sets the limits on each parameter. We also discuss specific
requirements on instrumentation, site and adaptive optics. In several cases, detailed simulated observations will be
required in order to set the requirements. While the example science cases provide a useful guide, we also note that an
important goal is to develop a facility that covers a broad parameter space, and maintains flexibility in order to adapt to
new scientific directions.
The second decade of the third millennium AD will hopefully see a new generation of ground-based telescopes, from 20- to 100-m in diameter, that will open a completely new window on the Universe. Here I review the scientific as well as technological drivers that underlie the new projects, looking at how they interact in pushing the limits of the parameter space and in driving the design requirements, and at some of the challenges they bring. As one may expect, much of the preparatory work, both design and industrial, is largely "concept independent", indicating that synergy rather than competition is the way forward (as it is already seen from the various collaborations that have been forming in the past year). While one should not underestimate the technical challenges, the promising result of many studies so far is that the only clearly identified show stopper seems to be funding.
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.
Even as a number of 8- to 10-m class telescopes come into operation worldwide, the scientific challenges these instruments and their space-based counterparts already address imply that future increases in light-gathering power and resolution will have to exceed conventional scaling factors. Indeed, it can be expected that the same progress in telescope diameter and resolution achieved throughout the century must now be realized within, at most, one or two decades. The technologies required to assert the validity of such an extrapolation appear to be within reach. Large telescopes successfully comissioned within the last decade have demonstrated key technologies such as active optics and segmentation. Furthermore, current design methods and fabrication processes imply that the technological challenge of constructing telescopes up to the 100-m range could, in some critical areas, be lower than those underlying, two decades ago, the design and construction of 8 to 10-m class telescopes. At system level, however, such giants are no size-extrapolated fusion of VLT and Keck, but fully integrated adaptive systems. In this paper we elaborate on some of the science drivers behind the OWL concept of a 100-m telescope with integrated adaptive optics capability. We identify major conceptual differences with classical, non-adaptive telescopes, and derive design drivers accordingly. We also discuss critical system and fabrication aspects, and the possible timeline for the concept to be realized.
High-z galaxies beyond redshift ~ 4 are essentially detected from ground based observations through their Lyα emission. The anticipated Lyα flux of galaxies at redshifts ~ 6 and beyond is a few times 0.1 10-17 ergs.s-1.cm-2 and its detection requires observations in low background conditions, when the observing wavelength is pushed into the near IR domain. We have carried out observations on 4-8 m telescopes to search for high z galaxies at 920 nm, 1060 and 1187 nm, resorting to various techniques: Narrow Band (NB) imaging and multi-slit windows. Observations, data reduction and preliminary results are described.
Multi-Conjugate Adaptive Optics (MCAO) is working on the principle to perform wide field of view atmospheric turbulence correction using many Guide Stars located in and/or surrounding the observed target. The vertical distribution of the atmospheric turbulence is reconstructed by observing several guide stars and the correction is applied by some deformable mirrors optically conjugated at different altitudes above the telescope.
The European Southern Observatory together with external research institutions is going to build a Multi-Conjugate Adaptive Optics Demonstrator (MAD) to perform wide field of view adaptive optics correction. The aim of MAD is to demonstrate on the sky the feasibility of the MCAO technique and to evaluate all the critical aspects in building such kind of instrument in the framework of both the 2nd generation VLT instrumentation and the 100-m telescope OWL.
In this paper we present the conceptual design of the MAD module that will be installed at one of the VLT unit telescope in Paranal to perform on-sky observations. MAD is based on a two deformable mirrors correction system and on two multi-reference wavefront sensors capable to observe simultaneously some pre-selected configurations of Natural Guide Stars. MAD is expected to correct up to 2 arcmin field of view in K band.
Extremely large filled-aperture ground-based optical-IR telescopes, or ELTs, ranging from 20 to 100m in diameter, are now being proposed. The all-important choice of the aperture must clearly be driven by the potential science offered. We here highlight science goals from the Leiden Workshop in May 2001 suggesting that for certain critical observations the largest possible aperture - assumed to be 100m (the proposed European OverWhelmingly Large telescope (OWL) - is strongly to be desired. Examples from a long list include:
* Identifying the first sources of ionisation in the universe, out to z ≥14
* Identifying and stufdying the first generation of dusty galaxies
* More speculatively, observing the formation of the laws of physics, via the evolution of the fundamental physical contants in the very early Universe, by high-resolution spectroscopy of very distant quasars.
*Determining detailed star-formation histories of galaxies out to the Virtgo Cluster, and hence for all major galaxy types (not just those available close to the Local Group of galaxies).
THE SOLAR SYSTEM: A 100-m telescope would do the work of a flotilla of fly-by space probes for investigations ranging from the evolution of planetary sutfaces and atmospheres to detailed surface spectroscopy of Kuiper Belt Objects. (Such studies could easily occupy it full-time.)
EARTHLIKE PLANETS OF NEARBY STARS: A propsect so exciting as perhaps to justify the 100-m telescope on its own, is that of the direct detection of earthlike planets of solar-type stars by imaging, out to at least 25 parsecs (80 light years) from the sun, followed by spectroscopic and photometric searches for the signature of life on the surfaces of nearer examples.
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).
On August 8, 2001, Melipal became the fourth Unit Telescope of ESO's VLT to start regular scientific operations. Accordingly, the Paranal Science Operations team is now providing support for execution of observation programmes of the astronomical community on all four individual 8 m telescopes of the VLT. The operational model developed and applied by this team is based on the concept that optimal exploitation of the unique potential of the VLT and of its instrumentation requires support by dedicated qualified and experienced astronomers. This applies to observing both in visitor mode and in service (queue) mode, between which VLT operations are shared approximately in a 50/50 proportion. The Paranal Science Operations team has been staffed to implement the above-mentioned operational concept in collaboration with a mountain-based engineering team for technical support, and with groups based at ESO's headquarters in Germany for front- and back-end contacts with the astronomical community. Together with these teams, and based on the experience acquired since the start of operations of the first UT in April 1999, operational procedures have been refined and new operational tools have been implemented. In this process, the aspects that are particularly revelant for on-site operations include the short-term scheduling of service mode operations, and the reporting and tracking of the service mode programme execution status.
The end-to-end operations of the ESO VLT has now seen three full years of service to the ESO community. During that time its capabilities have grown to four 8.2m unit telescopes with a complement of four optical and IR multimode instruments being operated in a mixed Service Mode and Visitor Mode environment. The input and output of programs and data to the system is summarized over this period together with the growth in operations manpower. We review the difficulties of working in a mixed operations and development environment and the ways in which the success of the end-to-end approach may be measured. Finally we summarize the operational lessons learned and the challenges posed by future developments of VLT instruments and facilities such as interferometry and survey telescopes.
The European Southern Observatory is developing a concept of ground-based, 100-m class optical telescope, with segmented primary and secondary mirrors, integrated active optics and multi-conjugate adaptive optics capabilities. Preliminary analysis have confirmed feasibility of the major telescope components within a cost on the order of 1,000 million Euros and within a competitive time frame. The modular design allows progressive transition between integration and science operation, and the telescope would be able to deliver full resolution and unequalled collecting power 11 to 12 years after project funding. The concept owes much of its design characteristics to features of existing telescopes, namely the Hobby-Eberly for optical fabrication, the Keck for optical segmentation, and the VLT for active optics control. The only critical area in terms of needed development seems to be multi-conjugate adaptive optics, but its principles have recently been confirmed experimentally and rapid progress in the underlying technologies is taking place and benefits from consumer applications. Further studies are progressing, confirming initial estimates, and a baseline design is taking shape. The primary objective of those studies is to demonstrate feasibility within proven technologies, but provisions are made for likely technological progress allowing either cost reduction or performance improvement, or both.
On 31 March 2000, the ESO Very Large Telescope (VLT) will complete the first year of science operations. During this first year, Antu (UT1) was operated with two instruments: Focal Reducer/Low Resolution Spectrograph (FORS-1) and Infrared Spectrograph and Array Camera (ISAAC). Both Visitor and Service Mode operations were successfully supported, with roughly equal time spent in each mode. On 1 April 2000, Kueyen (UT2) will begin science operations with two new instruments: UV-Visible Echelle Spectrograph (UVES) and FORS-2. The VLT science operations concept revolves around a distributed operations model. Front-end (proposal, observation, and scheduling preparation support and management) and back-end (quality control, Service Mode data distribution, and archive) operations are executed at ESO headquarters in Garching bei Munchen, Germany. Observation execution and on-line quality control are managed on-site at the Paranal Observatory, Cerro Paranal, Chile. The VLT Data Flow System provides the backbone infrastructure for VLT operations. Here we present an overview of the VLT science operations concept, a summary of the results from Year 1, and a discussion of lessons learned and where the science operations concept had to be adapted to achieve the current level of operations.
The next generation of ground based telescopes will break the 20th century paradigm of the 'factor of two' diameter increase. Taking advantage of the enormous advances in technology that the present generation of 8-10m telescopes has fostered, they will be fully adaptive, fully steerable behemoths of up to 100m diameter performing at the diffraction limit in the optical and near IR. At ten times the collecting area of every telescope ever built put together, they will have limiting magnitudes of 37-38, angular resolution of 1-2 milliarcseconds, and a price tag that does not follow the historical D2.6 cost law. In this paper we discuss some of the possible science cases for a telescope of 100m. Among them the determination of H unencumbered by local effects, the study of every SN ever exploded at any z < 10, the spectroscopy of extra-solar planets, studies of ultrahigh frequency phenomena, imaging of stellar surfaces, detection of brown dwarfs in external galaxies. The advent of the next generation of Extremely Large Telescopes will probably substantially change the operation all paradigm of astronomical observations, expanding on the present trend towards large programs, much in the way particle physics has gone with the large accelerators.
We explore the scientific case and the conceptual feasibility of giant filled aperture telescopes, in the light of science goals needing an order of magnitude increase in aperture size, and investigate the requirements (and challenges) these imply for possible technical options in the case of a 100 m telescope. The 100-m f/6.4 telescope optical concept is of a four mirror design with segmented, spherical primary and secondary mirrors, and 8-m class aspheric tertiary and quaternary mirrors, providing a 3 arc minutes field of view. Building on the experience of the VLT and other large telescope projects, we investigate mirror fabrication issues, a possible mechanical solution, the requirements for the absolutely essential adaptive optics system and for the instrumentation package, and the implications for budget and schedule.
An overview of the scientific goals and specifications of the instruments to be installed on the two Nasmyth foci of the Unit Telescope 2 of the VLT is presented. The combination of a fiber position with three independent spectrographs provides a powerful utility for multi-object spectroscopy of large samples. Two spectrographs will cover the optical and infrared regime at medium resolution and a fiber link to the echelle spectrograph mounted on the second Nasmyth focus will permit multiplexing observations at high spectral resolution.