| 1. |
- Andersen, Torben, et al.
(författare)
-
A parallel integrated model of the Euro50
- 2004
-
Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5497:1, s. 251-265
-
Konferensbidrag (refereegranskat)abstract
- The Euro50 is an astronomical extremely large telescope for optical and infrared wavelength with a 50 m primary mirror. The telescope will have an elaborate control system ("live optics") to correct for atmospheric and telescope aberrations. To study and predict performance of the complete telescope system, an integrated model combining the structural model of the telescope, optics models, the control systems, and the adaptive optics has been established. Wind is taken into account on the basis of wind tunnel measurements and computer fluid dynamics calculations. Atmospheric aberrations are included using a seven-layer atmosphere model. The integrated model is written in Matlab and is run on a cluster computer to achieve acceptable execution times. Dedicated ordinary differential equation solvers have been written and a special toolkit for communication between Matlab processes on different nodes of the cluster computer has been set up. Preliminary results from the complete integrated model, including adaptive optics, are shown
|
|
| 2. |
- Andersen, Torben, et al.
(författare)
-
Integrated modeling of the Euro50
- 2003
-
Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5382:1, s. 366-378
-
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
|
|
| 3. |
- Andersen, Torben, et al.
(författare)
-
Status of the Euro50 project
- 2004
-
Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5489:1, s. 407-416
-
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
|
|
| 4. |
|
|
| 5. |
- Beckers, Jacques M, et al.
(författare)
-
Rapid refocusing system for the Euro50 telescope aimed at removing the perspective elongation of laser beacons
- 2003
-
Ingår i: Society of Photo-Optical Instrumentation Engineers. Proceedings. - : SPIE. - 0361-0748. ; 5169, s. 123-136
-
Tidskriftsartikel (refereegranskat)abstract
- To obtain full sky coverage, astronomical adaptive optics systemsrequire Na Sodium Beacons (SBs) (also referred to as Laser Guide Starsor LGSs) located at heights extending from 85 to 100 km. When viewed atthe edge of large telescopes these SBs appear elongated. For the Euro5050 meter aperture telescopes this elongation amounts to 6 to 9arcseconds when the laser is launched from a point on the telescopeaxis. This is substantially larger than the ~0.6 arcsec FWHM SB whenviewed near the telescope center. This so-called "perspectiveelongation" substantially decreases the sensitivity of SB aided adaptiveoptics. We describe a way of removing this elongation when using pulsedlasers. It uses rapid (microsecond) refocusing of the telescope with theaid of birefringent lenses and polarization modulators. We present anoutline of the SB wavefront sensor for the Euro50.
|
|
| 6. |
- Beckers, Jacques M., et al.
(författare)
-
Sodium beacon wavefront sensing for the Euro50 telescope in the presence of perspective elongation
- 2004
-
Ingår i: Proceedings of the SPIE. - : SPIE. - 0819452998 ; 5382, s. 510-519
-
Konferensbidrag (refereegranskat)abstract
- To obtain full sky coverage, astronomical adaptive optics systemsrequire Na Sodium Beacons (SBs) (also referred to as Laser Guide Starsor LGSs) located at heights extending from 85 to 100 km. When viewed atthe edge of large telescopes these SBs appear elongated. For the Euro5050 meter aperture telecopes this elongation amounts to 6 to 9 arcsecondswhen the laser is launched from a point on the telescope axis. This issubstantially larger than the -0.6 arcsec FWHM SB when viewed near thetelescope center. This so-called "perspective elongation" substantiallydecreases the sensitivity of SB aided adaptive optics. We describe a wayof removing this elongation when using pulsed lasers. It uses rapid(microsecond) refocusing of the telescope with the aid of birefringentlenses and polarization modulators. We present an outline of the SBwavefront sensor for the Euro50.
|
|
| 7. |
- Beckers, Jacques M., et al.
(författare)
-
Very high-resolution spectroscopy for extremely large telescopes using pupil slicing and adaptive optics
- 2007
-
Ingår i: Optics Express. - 1094-4087. ; 15:5, s. 1983-1994
-
Tidskriftsartikel (refereegranskat)abstract
- Under seeing limited conditions very high resolution spectroscopy becomes very difficult for extremely large telescopes (ELTs). Using adaptive optics (AO) the stellar image size decreases proportional with the telescope diameter. This makes the spectrograph optics and hence its resolution independent of the telescope diameter. However AO for use with ELTs at visible wavelengths require deformable mirrors with many elements. Those are not likely to be available for quite some time. We propose to use the pupil slicing technique to create a number of sub-pupils each of which having its own deformable mirror. The images from all subpupils are combined incoherently with a diameter corresponding to the diffraction limit of the sub-pupil. The technique is referred to as "Pupil Slicing Adaptive Optics" or PSAO. (c) 2007 Optical Society of America.
|
|
| 8. |
- Darudi, Ahmad, et al.
(författare)
-
The Robotic Earthshine Telescope
- 2010
-
Ingår i: Proceedings of the SPIE. - : SPIE. - 1996-756X .- 0277-786X. ; 7733, s. 8-77332
-
Konferensbidrag (refereegranskat)abstract
- Lund Observatory is presently designing and constructing a robotic telescope dedicated to studies of the Earth's albedo by measuring the ratio between the intensity of the dark and bright sides of the Moon. The telescope will operate both in broadband and narrow-band modes over the entire visible wavelength range and will transmit observational results back to the operation team over the Internet. Design challenges, in particular related to choice of CCD and stray light suppression, are described, together with the design of the optics, control system, and enclosure. Finally we present results from laboratory tests. The telescope will go into operation in the first half of 2011.
|
|
| 9. |
- Gontcharov, Alexander, et al.
(författare)
-
Adaptive optics for the Euro50: design and performance
- 2003
-
Ingår i: Future Giant Telescopes. Proceedings of the SPIE. - : SPIE. - 081944619X ; 4840, s. 36-46
-
Konferensbidrag (refereegranskat)abstract
- The optical design for the proposed Euro50 extremely large telescopewith integrated adaptive optics (AO) is presented. For atmosphericturbulence correction, we propose using single and dual-conjugate AOsystems working with natural and laser guide stars. The corrective shapeof the deformable mirrors (DMs) is derived from an analytical algorithmbased on minimization of the sum of the residual power spectra of thephase fluctuations seen by guide stars after correction. Predictions forperformance of the Euro50 ELT with Dual-conjugate AO are given for the Kband using a seven layer atmospheric model for the atmosphere at theObservatorio del Roque de los Muchachos (ORM) on La Palma. The averageStrehl ratio is used to quantify the system performance for differentvalues of actuator pitch and DM conjugation altitudes. The influence ofthe outer scale and telescope pointing on the RMS stroke of the DMs ispresented. It is concluded that construction of such a system isfeasible and that there is a need for development of a simulation toolto verify the analytical calculations. Precise knowledge of the outerscale of the atmosphere at the ORM is needed to establish the dynamicalrange of the mirrors.
|
|
| 10. |
- Knutsson, Per, 1978, et al.
(författare)
-
Correction of static and non-common path aberrations in an adaptive optics system using inherent calibration data
- 2021
-
Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 29:3, s. 3406-3414
-
Tidskriftsartikel (refereegranskat)abstract
- For low-order adaptive optics systems, a method that is able to correct for system aberrations in the final focal plane is presented. The paper presents a novel figure of merit, corresponding to the integrated non-normalized tip-tilt-free optical transfer function. The inherent singular value decomposition modal content of the interaction matrix is used to optimize this figure of merit. The method has proven to be stable and robust, providing a simple mean to facilitate diffraction limited imaging in an experimental setup for ophthalmic applications. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
|
|
