METIS is a mid-infrared instrument proposed for the European Extremely Large Telescope (E-ELT). It is designed to
provide imaging and spectroscopic capabilities in the 3μm to 14μm region up to a spectral resolution of 100.000. Here
the technical concept of METIS is described which has been developed based on an elaborated science case which is
presented elsewhere in this conference.
There are five main opto-mechanical modules all integrated into a common cryostat: The fore-optics is re-imaging the
telescope focal plane into the cryostat, including a chopper, an optical de-rotator and an un-dispersed pupil stop. The
imager module provides diffraction limited direct imaging, low-resolution grism spectroscopy, polarimetry and
coronagraphy. The high resolution IFU spectrograph offers a spectral resolution of 100.000 for L- and M-band and
optional 50.000 for the N-band. In addition to the WFS integrated into the E-ELT, there is a METIS internal on-axis
WFS operating at visual wavelengths. Finally, a cold (and an external warm) calibration unit is providing all kinds of
spatial and spectral calibrations capabilities. METIS is planned to be used at one of the direct Nasmyth foci available at
This recently finished Phase-A study carried out within the framework of the ESO sponsored E-ELT instrumentation
studies has been performed by an international consortium with institutes from Germany, Netherlands, France, United
Kingdom and Belgium.
METIS is the 'Mid-infrared ELT Imager and Spectrograph', the only planned thermal/mid-IR instrument for the E-ELT.
METIS will provide diffraction limited imaging in the atmospheric L/M and N-band from 3 - 14 μm over an 18"×18"
field of view (FOV). The imager also includes high contrast coronagraphy and low-resolution (900 ≤ R ≤ 5000) long slit
spectroscopy and polarimetry. In addition, an IFU fed, high resolution spectrograph at L/M band will provide a spectral
resolution of R ~ 100,000 over a 0.4"×1.5" FOV. The adaptive optics (AO) system is relatively simple, and METIS can
reach its full performance with the adaptive correction provided by the telescope - and occasionally even under seeing
limited conditions. On a 42m ELT, METIS will provide state-of-the-art mid-IR performance from the ground. The
science case for METIS is based on proto-planetary disks, characterization of exoplanets, formation of our Solar System,
growth of supermassive black holes, and the dynamics of high-z galaxies. With the focus on highest angular resolution
and highest spectral resolution, METIS is highly complementary to JWST and ALMA. This paper summarizes the
science case for METIS, and describes the instrument concept, performance and operational aspects.
METIS, the Mid-infrared ELT Imager and Spectrograph (formerly called MIDIR), is a proposed instrument for the
European Extremely Large Telescope (E-ELT), currently undergoing a phase-A study. The study is carried out within
the framework of the ESO-sponsored E-ELT instrumentation studies. METIS will be designed to cover the E-ELT
science needs at wavelengths longward of 3μm, where the thermal background requires different operating schemes. In
this paper we discuss the main science drivers from which the instrument baseline has been derived. Specific emphasis
has been given to observations that require very high spatial and spectral resolution, which can only be achieved with a
ground-based ELT. We also discuss the challenging aspects of background suppression techniques, adaptive optics in
the mid-IR, and telescope site considerations. The METIS instrument baseline includes imaging and spectroscopy at the
atmospheric L, M, and N bands with a possible extension to Q band imaging. Both coronagraphy and polarimetry are
also being considered. However, we note that the concept is still not yet fully consolidated. The METIS studies are
being performed by an international consortium with institutes from the Netherlands, Germany, France, United
Kingdom, and Belgium.
On the way to the Extremely Large Telescopes (ELT) the Large Binocular
Telescope (LBT) is an intermediate step. The two 8.4m mirrors create a masked aperture of 23m. LINC-NIRVANA is an instrument taking advantage of this opportunity. It will get, by means of Multi-Conjugated Adaptive Optics (MCAO), a moderate Strehl Ratio over a 2 arcmin field of view, which is used for Fizeau (imaging) interferometry in J,H and K. Several MCAO concepts, which are
proposed for ELTs, will be proven with this instrument. Studies of sub-systems are done in the laboratory and the option to test them on sky are kept open. We will show the implementation of the MCAO concepts and control aspects of the instrument and present the road map to the final installation at LBT. Major milestones of LINC-NIRVANA, like preliminary design review or final design review are already done or in preparation. LINC-NIRVANA is one of the
few MCAO instruments in the world which will see first light and go into operation within the next years.
LINC-NIRVANA is an imaging interferometer for the Large Binocular Telescope (LBT) and will make use of multi-conjugated adaptive optics (MCAO) with two 349 actuators deformable mirrors (DM), two 672 actuator deformable secondary mirrors and a total of 4 wavefront sensors (WFS) by using 8 or 12 natural guide stars each. The goal of the MCAO is to increase sky coverage and achieve a medium Strehl-ratio over the 2 arcmin field of view. To test the concepts and prototypes, a laboratory setup of one MCAO arm is being built. We present the layout of the MCAO prototype, planned and accomplished tests, especially for the used Xinetics DMs, and a possible setup for a test on sky with an existing 8m class telescope.
LINC-NIRVANA is a near-infrared (1-2.4 micron) beam-combiner instrument for the Large Binocular Telescope (LBT). LINC-NIRVANA is being built by a consortium of groups at the Max-Planck-Institut fur Astronomie in Heidelberg, the Osservatorio Astrofisico di Arcetri in Florence, the Universitat zu Koln, and the Max-Planck-Institut fur Radioastronomie in Bonn. The MPI fur Radioastronomie is responsible for the near-infrared detector for the fringe and flexure tracking system (FFTS).
We describe the design and construction of the detector control electronics as well as the first laboratory measurements of performance parameters of the NIR detector for the fringe and flexure tracking system of the LBT LINC-NIRVANA instrument. This detector has to record LBT interferograms of suitable reference stars in the FOV at a frame rate of the order of 200 frames per second using, for example, 32 x 32-pixel subframes. Moreover, special noise reduction techniques have to be applied. The fringe-tracker interferograms are required for monitoring and closed-loop correction of the atmospheric optical path difference of the two LBT wavefronts (see C. Straubmeier et al., "A fringe and flexure tracking system for LINC-NIRVANA: basic design and principle of operation"). We will describe our laboratory measurements of maximum frame rate, readout noise, photometric stability, and other important parameters together with first measurements of laboratory simulations of LBT interferograms.
Layer Oriented represented in the last few years a new and promising aproach to solve the problems related to the limited field of view achieved by classical Adaptive Optics systems. It is basically a different approach to multi conjugate adaptive optics, in which pupil plane wavefront sensors (like the pyramid one) are conjugated to the same altitudes as the deformable mirrors. Each wavefront sensor is independently driving its conjugated deformable mirror thus simplifying strongly the complexity of the wavefront computers used to reconstruct the deformations and drive the mirror themselves, fact that can become very important in the case of extremely large telescopes where the complexity is a serious issue. The fact of using pupil plane wavefront sensors allow for optical co-addition of the light at the level of the detector thus increasing the SNR of the system and permitting the usage of faint stars, improving the efficiency of the wavefront sensor. Furthermore if coupled to the Pyramid wavefront sensor (because of its high sensitivity), this technique is actually peforming a very efficient usage of the light leading to the expectation that, even by using only natural guide stars, a good sky coverage can be achieved, above all in the case of giant telescopes. These are the main reasons for which in the last two years several projects decided to make MCAO systems based on the Layer Oriented technique. This is the case of MAD (an MCAO demonstrator that ESO is building with one wavefront sensing channel based on the Layer Oriented concept) and NIRVANA (an instrument for LBT). Few months ago we built and successfully tested a first prototype of a layer oriented wavefront sensor and experiments and demonstrations on the sky are foreseen even before the effective first light of the above mentioned instruments. The current situation of all these projects is presented, including the extensive laboratory testing and the on-going experiments on the sky.
LINC-NIRVANA is a Fizeau interferometer which will be built for the Large Binocular Telescope (LBT). The LBT exists of two 8.4m mirrors on one mounting with a distance of 22.8m between the outer edges of the two mirrors. The interferometric technique used in LINC-NIRVANA provides direct imaging with the resolution of a 23m telescope in one direction and 8.4m in the other. The instrument uses multi-conjugated adaptive optics (MCAO) to increase the sky coverage and achieve the diffraction limit in J, H, K over a moderate Field of View (2 arcmin in diameter). During the preliminary design phase the team faced several problems similar to those for an instrument at a 23m telescope. We will give an overview of the current design, explain problems related to 20m class telescopes and present solutions.
We are currently working on four projects employing Multi Conjugate Adaptive Optics in a Layer-Oriented fashion. These ranges from experimental validations, to demonstration facility or full instrument to be offered to an astronomical community and involves telescopes in the range of 4m to 24m equivalent telescope aperture. The current status of these projects along with their brief description is here given.
Since April 2001 a Large Program for the study of physical properties of Trans-Neptunian Objects (TNO) and Centaurs is underway at the Paranal (Very Large Telescope VLT) and La Silla (New Technology Telescope NTT) observatories of the European Southern Observatory (ESO) in Chile. Combining service (SM) and visitor mode (VM) observations multi-wavelength imaging (BVRIJHK filters) and low-dispersion spectroscopy is performed in the visible and near-IR on a sample of objects that should allow a better and more consistent taxonomic characterization and classification of these pristine bodies in our solar system.
Starting with a summary of the current knowledge on the Kuiper-Belt and the populations of objects, the paper presents the goals of this project and its scientific and organizational implementation. It illustrates the progress and the scientific achievements by a hynoptic view of results from photometry and spectroscopy of these Solar System objects.
One of the most critical issues in designing a spectrograph is the motion of opto-mechanical components due to flexure especially when it will be mounted to the Cassegrain focus of a telescope. Image motion on the detector has to be kept small in order not to affect the value of the scientific data. The FORS spectrographs fulfil those requirements by a proper design and by a passive compensation of the instrumental flexure. Image motion of the 2 metric tons instrument could be reduced in this way to a tiny fraction of one pixel's size thus not affecting the data gathered with those spectrographs. It is tested and approved at a telescope simulator that all specifications regarding those motions are fully met. A fine tuning flexure compensation is built into the spectrograph's design and is tested on its tuning range which allows to adapt the compensation to effects eventually caused by the Cassegrain flange of the telescope.
FORS1 (FOcal Reducer/low-dispersion Spectrograph) is an all dioptric focal reducer designed for direct imaging, low- dispersion multi-object spectroscopy, imaging polarimetry and spectro-polarimetry of faint objects. Two identical copies of the instrument (FORS 1 and 2) are being built by a consortium of three astronomical institutes (Landessternwarte Heidelberg and the University Observatories of Gottingen and Munich) under contract and in cooperation with ESO. FORS 1 and 2 will be installed, respectively, in 1998 and 2000 at the Cassegrain foci of the ESO VLT unit telescopes nos. 1 and 2. For the tests of FORS in Europe, a telescope and star simulator was built, which allows to incline and rotate the whole instrument and to simulate stars in the field of view at various seeing conditions. FORS 1 was integrated at the telescope simulator and saw its 'first light' in the integration facility in November 1996. Since then the electro-mechanical functions, the image motion due to flexure, the calibration units, the optical performance and the instrument software were tested and optimized. This paper presents a summary of the procedure and the results of the tests.
The hardware construction of FORS1, the first of the two focal reducer/low dispersion spectrographs of the ESO very large telescope (VLT), is now finished. An extensive testing program is under way which will guarantee that the instrument is fully understood and well calibrated when it will be installed at the Cassegrain focus of the first unit telescope of the VLT in 1998. This program includes a full characterization of the optical system and the evaluation of the setting accuracies and reproducibility of the numerous electromechanical functions as well as testing the flexure compensation which will minimize image shift during telescope motions. Telescope and star simulators were specially built for this purpose in order to test the optical and mechanical behavior of the instrument on the 8 m-telescope. Acceptance tests of the optical performance and the subsystem tests of all electromechanical functions indicate an excellent quality, especially for the complex multi object spectroscopy unit, while the overall system tests are just starting.