| 1. |
- Andersen, Torben, et al.
(författare)
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Euro50
- 2003
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 5382:1, s. 169-182
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Konferensbidrag (refereegranskat)abstract
- The Euro50 is a telescope for optical and infrared wavelengths. It has an aspherical primary mirror with a size of 50 meters and 618 segments. The optical configuration is of Gregorian type and the secondary mirror is deformable for adaptive optics. Observations can take place in prime focus, Gregorian foci, and Nasmyth foci using additional relay mirrors. The telescope provides seeing limited observations, partial adaptive optics with ground layer correction, single conjugate adaptive optics and dual-conjugate adaptive optics. For prime focus observations, a clam-shell corrector with a doublet lens is used. The primary mirror segments can be polished using the precessions polishing technique. "Live Optics" denotes the joint segment alignment system, secondary mirror control system, adaptive optics and main axes servos. An overview is given of the live optics architecture, including feedback from wavefront sensors for natural and laser guide stars, and from primary mirror segment edge sensors. A straw man concept of the laser guide star system using sum-frequency YAG lasers is presented together with a solution to the laser guide star perspective elongation problem. The structural design involves a large steel structure and a tripod of carbon fiber reinforced polymer to support the secondary mirror. Integrated models have been set up to simulate telescope performance. Results show that an enclosure is needed to protect the telescope against wind during observations. The enclosure is very large box-shaped steel structure
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| 2. |
- Ardeberg, Arne, et al.
(författare)
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Clusters as probes of distance, evolution, and chemistry of galaxies
- 2003
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 5382:1, s. 47-56
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Konferensbidrag (refereegranskat)abstract
- Stellar clusters are highly useful as tools for determination of distances, ages and abundances of heavy elements of galaxies, also at larger distances. Their utility for these purposes has, so far, been severely limited, mainly due to image crowding. The introduction of Extremely Large Telescopes (ELTs) with full adaptive optics (AO) and near diffraction limited performance should imply a drastic improvement concerning the usefulness of clusters and the limiting distances of high quality data. We have made a study of stellar clusters as probes of distance, evolution and chemistry of galaxies at distances from one to twenty Mpc. From data on the Stromgren uvby system, partly from direct measurements taken from the literature, we have synthesized test clusters, one open and one globular, as well as galactic backgrounds. The clusters have been embedded in the backgrounds and located at distances between one and twenty Mpc. Here, vby data have been measured, reduced and analyzed. Color-magnitude diagrams (CMDs), metallicity diagrams (MDs) and luminosity functions (LFs) have been constructed. They have been evaluated absolutely and compared to the corresponding template data. We conclude that with a 50 m AO ELT, for open as well as globular clusters, MDs are of high quality for clusters out to and beyond 5 Mpc and useful out to 10 Mpc. CMDs are of very high quality well beyond 5 Mpc. They are of high scientific value out to and beyond 10 Mpc and valuable for clusters even out to 20 Mpc. LFs are highly informative well beyond 10 Mpc and still rather valuable at 20 Mpc. With sufficient measurement data available, LFs are useful for clusters in galaxies even beyond 20 Mpc
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| 3. |
- Ardeberg, Arne, et al.
(författare)
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Science drivers of a 50-m AO telescope
- 2003
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 5382:1, s. 37-46
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Konferensbidrag (refereegranskat)abstract
- Some leading science programs undertaken with Very Large Telescopes and challenges driving the progress of the Extremely Large Telescopes are discussed together with the corresponding requirements. They concern expolanets, Earth-like planets, habitable zones, formation of stars and galaxies, first stars and cosmology. A description is attempted
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| 4. |
- Andersen, Torben, et al.
(författare)
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A new concept for large deformable mirrors for extremely large telescopes
- 2006
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 6272:1, s. 324-331
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Konferensbidrag (refereegranskat)abstract
- For extremely large telescopes, there is strong need for thin deformable mirrors in the 3-4 m class. So far, feasibility of such mirrors has not been demonstrated. Extrapolation from existing techniques suggests that the mirrors could be highly expensive. We give a progress report on a study of an approach for construction of large deformable mirrors with a moderate cost. We have developed low-cost actuators and deflection sensors that can absorb mounting tolerances in the millimeter range, and we have tested prototypes in the laboratory. Studies of control laws for mirrors with thousands of sensors and actuators are in good progress and simulations have been carried out. Manufacturing of thin, glass mirror blanks is being studied and first prototypes have been produced by a slumping technique. Development of polishing procedures for thin mirrors is in progress
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| 5. |
- Andersen, Torben, et al.
(författare)
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Integrated modeling of the Euro50
- 2003
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5382:1, s. 366-378
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Konferensbidrag (refereegranskat)abstract
- The Euro50 is a proposed 50 m optical and infrared telescope. It will have thousands of control loops to keep the optics aligned under influence of wind, gravity and thermal loads. Cross-disciplinary integrated modeling is used to study the overall performance of the Euro50. A sub-model of the mechanical structure originates from finite element modeling. The optical performance is determined using ray tracing, both non-linear and linearized. The primary mirror segment alignment control system is modeled with the 618 segments taken as rigid bodies. Adaptive optics is included using a layered model of the atmosphere and sub-models of the wavefront sensor, reconstructor and controller. The deformable mirror is, so far, described by a simple influence function and a second order dynamical transfer function but more detailed work is in progress. The model has been implemented using Matlab/Simulink on individual computers but it will shortly be implemented on a Beowulf cluster within a trusted network. Communication routines between Matlab on the cluster processors have been written and are being benchmarked. Representative results from the simulations are shown
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| 6. |
- Andersen, Torben, et al.
(författare)
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Status of the Euro50 project
- 2004
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5489:1, s. 407-416
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Konferensbidrag (refereegranskat)abstract
- The Euro50 is an extremely large telescope for optical and infrared wavelength with a 50 m primary mirror. It has a segmented, aspherical primary mirror and an aspherical, deformable secondary in a Gregorian layout. A tentative conceptual design exists and has been documented in a study report. Recent activities have concentrated on the science case for extremely large telescopes in the 50 m class and on identification of potential technical "show stoppers". The science case investigation has identified four fields of particular interest. The studies of critical technical issues have concentrated on atmospheric dispersion effects for high-resolution adaptive optics for extremely large telescopes, and on the influence of wind and other disturbances on wavefront control. Wind load on the telescope, the primary mirror and the enclosure has been studied using wind tunnel measurements and computational fluid dynamics. The impact of wind on the total system has been investigated using an integrated model that includes the telescope structure, the primary mirror segment alignment system, the secondary mirror alignment system, and single conjugate adaptive optics using the deformable secondary mirror. The first, tentative results show that wind disturbances may be significant and that the task of correcting for wind residuals may be at least as large for the adaptive optics system as that of correcting for atmospheric aberrations. The results suggest that use of extremely large telescopes for observations of earth-like planets around nearby stars may imply a considerable challenge
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| 7. |
- Ardeberg, Arne, et al.
(författare)
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Diffraction-limited light collection: Promises and challenges of a 50 m ELT
- 2004
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 1996-756X .- 0277-786X. ; 5489:PART 1, s. 23-34
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Konferensbidrag (refereegranskat)abstract
- Programmes driving ELT design are discussed. The nature and evolution of circum-stellar shells and planetary discs are attractive, while the small angular sizes place basic properties, asymmetry and warps, beyond VLT capability. An ELT is neeed to reveal the conversion processes shell - disc - planets, planetary systems, Earth-like planets, habitability and life signatures. Formation and evolution of massive stars are dicussed as are stellar rotation and shape, surface spatial and temporal resolution and evolution. Stellar clusters are discussed as probes of galactic evolution, resolving CMDs for Virgo and Fornax cluster galaxies. High-resolution studies of AGNs are discussed as are supernovae with bearing on early star formation, galactic activity and cosmology. Finally, the requirements defined from the prime science drivers are confronted with technical realities.
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| 8. |
- Ardeberg, Arne, et al.
(författare)
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ELTs, adaptive optics and wavelengths - art. no. 698608
- 2008
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Ingår i: Extremely Large Telescopes: Which Wavelengths? Retirement Symposium for Arne Ardeberg. - : SPIE. - 1996-756X .- 0277-786X. ; 6986, s. 98608-98608
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Konferensbidrag (refereegranskat)abstract
- A number of Extremely Large Telescopes for visual-infrared and adjacent wavelengths are in various degrees of progress. All have primary mirrors with equivalent diameters larger than 20 m and are intended for operation with adaptive optics systems. We discuss several ELT observing parameters as functions of wavelength. Stellar energy distributions and atomic line spectra are inspected as are the transmission of the Earth's atmosphere, the emissivity of the sky and telescope and instruments as well as detector sensitivity, resolution and signal-to-noise ratio. The spatial resolution depending on the size of the diffraction limited adaptive optics point spread function is discussed. We have evaluated the ELT efficiency in terms of Johnson V to N band photometry, simulating diffraction-limited ELT images of a stellar field at 4 Mpc and 4 kpc, respectively. We conclude that the information content at shorter wavelengths is of dominant nature and that there is every reason to do the utmost to include shorter wavelengths in the AO regime. We propose to adopt a short-wave length goal of 1 000 nm for first light AO with later updates reaching down to visual wavelengths.
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| 9. |
- Ardeberg, Arne, et al.
(författare)
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Evolution of distant galaxies from cluster photometry: a program for a 50-m ELT
- 2004
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5489:1, s. 72-83
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Konferensbidrag (refereegranskat)abstract
- The formation, shaping and evolution of galaxies are processes of high interest but poorly known. This is true also for our closest galactic neighbours. Of key importance is a representative sample of all major types of galaxies with solid evolutionary parameters. Stellar clusters are excellent probes of galactic evolution, albeit so far useful at smaller distances only, mainly due to the limiting effects of image crowding. With extremely large telescopes (ELTs) with full adaptive optics (AO) and near diffraction limited performance, the effects of image crowding will be drastically reduced. Thus, the excellence of clusters of stars as evolutionary probes can be extended out to cosmological distances. We have studied this extension. With data on the Str
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| 10. |
- Ardeberg, Arne, et al.
(författare)
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From Euro50 towards a European ELT
- 2006
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6267 II, s. 26725-26725
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Konferensbidrag (refereegranskat)abstract
- With Euro50 as a convenient telescope laboratory, the Euro50 team has continued development aiming at a European extremely large telescope (ELT). Here, we give a progress report. The needs of science and instrumentation are briefly discussed as is the importance of photometric stability and precision. Results are reported from work on integrated modelling. Details are given concerning point-spread functions (PSFs) obtained with and without adaptive optics (AO). Our results are rather encouraging concerning AO photometry and compensation of edge sensor noise as well as regarding seeing-limited ELT operation. The current status of our development of large deformable mirrors is shown. Low-cost actuators and deflection sensors have been developed as have hierarchic control algorithms. Fabrication of large thin mirror blanks as well as polishing and handling of thin mirrors has been studied experimentally. Regarding adaptive optics, we discuss differential refraction and the limitations imposed by dispersive optical path differences (OPDs) and dispersive anisoplanatism. We report on progress in laser guide star (LGS) performance and a real-time online experiment in multi-conjugate AO (MCAO). We discuss ELTs, high-resolution spectroscopy and pupil slicing with and without use of AO. Finally, we present some recent studies of ELT enclosure options.
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