| 1. |
- Andersen, Torben, et al.
(författare)
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The Euro50 Extremely Large Telescope
- 2003
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Ingår i: Future Giant Telescopes. Proceedings of the SPIE.. - 081944619X ; 4840, s. 214-225
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Konferensbidrag (refereegranskat)abstract
- Euro50 is a proposed optical telescope with an equivalent primary mirrordiameter of 50 m. Partners of the collaboration are institutes inSweden, Spain, Ireland, Finland, and the UK. The telescope will have asegmented primary mirror and an aplanatic Gregorian configuration withtwo elliptical mirrors. For a 50 m telescope there would be noeconomical advantage in going to a spherical primary. The size of theprimary mirror segments (2 m) has been selected on the basis of aminimization of cost. An adaptive optics system will be integrated intothe telescope. The telescope will have three operational modes: Seeinglimited observations, single conjugate adaptive observations in theK-band, and dual conjugate observations also in the K-band. An upgradeto adaptive optics also in the visible down to 500 nm is foreseen. Therewill be an enclosure to protect the telescope against adverse weatherand wind disturbances. Integrated simulation models are underdevelopment. The project time will be 10 years and the cost some 591MEuros.
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| 2. |
- Gontcharov, Alexander, et al.
(författare)
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Adaptive optics for the Euro50: design and performance
- 2003
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Ingår i: Future Giant Telescopes. Proceedings of the SPIE. - : SPIE. - 081944619X ; 4840, s. 36-46
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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.
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| 3. |
- Hawarden, Timothy G., et al.
(författare)
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Critical science with the largest telescopes: science drivers for a 100m ground-based optical-IR telescope
- 2003
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Ingår i: Future Giant Telescopes (Proceedings of the SPIE). - : SPIE. - 081944619X ; 4840, s. 299-308
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Konferensbidrag (refereegranskat)abstract
- 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 (theproposed European OverWhelmingly Large telescope (OWL) - is strongly tobe desired. Examples from a long list include: COSMOLOGY: Identifying the first sources of ionisation in the universe, out to z >=14 Identifying and studying 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. NEARER GALAXIES: 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 ofplanetary 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 prospect so exciting as perhaps to justify the 100-m telescope on its own, is that of the direct detectionof 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.
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| 4. |
- Miller, Jeremiah E., et al.
(författare)
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Electron tunneling in rhenium-modified Pseudomonas aeruginosa azurins
- 2004
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 1655:1-3, s. 59-63
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Tidskriftsartikel (refereegranskat)abstract
- Laser flash-quench methods have been used to generate tyrosine and tryptophan radicals in structurally characterized rhenium-modified Pseudomonas aeruginosa azurins. Cu(I) to “Re(II)” electron tunneling in Re(H107) azurin occurs in the microsecond range. This reaction is much faster than that studied previously for Cu(I) to Ru(III) tunneling in Ru(H107) azurin, suggesting that a multistep (“hopping”) mechanism might be involved. Although a Y108 radical can be generated by flash-quenching a Re(H107)M(II) (M=Cu, Zn) protein, the evidence suggests that it is not an active intermediate in the enhanced Cu(I) oxidation. Rather, the likely explanation is rapid conversion of Re(II)(H107) to deprotonated Re(I)(H107 radical), followed by electron tunneling from Cu(I) to the hole in the imidazole ligand.
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| 5. |
- Owner-Petersen, Mette, et al.
(författare)
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Control strategy for the adaptive optics of the Euro50
- 2003
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Ingår i: Future Giant Telescopes. Proceedings of the SPIE. - : SPIE. - 081944619X ; 4840, s. 427-435
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Konferensbidrag (refereegranskat)abstract
- The scheme presently envisaged for the EURO50 adaptive optics ispresented. The Euro50 adaptive optics will primarily work with laserguide stars (LGSs) and control of either one or two deformable mirrors(SCAO and DCAO respectively), but operation using a natural guide star(NGS) is also foreseen. The point spread function (PSF) for SCAOoperation using a single NGS is evaluated. An algorithm for optimalcontrol of the deformable mirrors (DMs) using LGSs and Shack-Hartmanwavefront sensors is presented and commented upon. It is an extension ofa recently developed algorithm for optimal control using NGSs andworking in the spatial Fourier domain. In addition the concept of avirtual wavefront sensor is introduced to overcome the difficulty intransmitting a large number (37) of LGSs to the final DCAO focus withboth adequate field and adequate aberrations. The expected performanceis estimated in form of maps of the Strehl ratio versus field angleusing a standard seven layer atmospheric model for the Observatorio delRoque de los Muchachos (ORM) site on la Palma for the case of the outerscale being either 20 m (nominal for ORM) or infinity (Kolmogorov - mostpessimistic case).
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