Dr. Nancy Ageorges Profile

Dr. Nancy Ageorges

at Kampf Telescope Optics GmbH

SPIE Involvement:

Author

Publications (39)

Proceedings Article | 26 August 2024 Presentation + Paper

Presentation + Paper

The MICADO first light imager for the ELT: the detector positioning system of MICADO

Aysun Sönmez, Florian Lang, Sebastian Rabien, Kateryna Kravchenko, Andreas Emslander, Federico Biondi, Mathias Honsberg, Matthias Deysenroth, Luis Neumeier, Lenard Spallek, Lothar Barl, Naidu Bezawada, Veronika Wimmer, Marcus Haug, Nancy Ageorges, Dirk Kampf

Proceedings Volume 13100, 1310036 (2024) https://doi.org/10.1117/12.3018338

KEYWORDS: Sensors, Interfaces, Cryostats, Detector arrays, Cryogenics, Actuators, Computer aided design, Retroreflectors

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Proceedings Article | 23 August 2024 Poster + Paper

Poster + Paper

Membrane space telescope: case study of a deployable large aperture

N. Ageorges, S. Eberle, D. Kampf, S. Rabien

Proceedings Volume 13092, 130925P (2024) https://doi.org/10.1117/12.3019764

KEYWORDS: Parabolic mirrors, Space mirrors, Space telescopes, Mirrors, Telescopes, Prototyping, Mirror surfaces, Deformable mirrors, Mirror mounts, Distortion

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Proceedings Article | 12 March 2024 Poster + Paper

Poster + Paper

GEOStar: demonstration of laser guide star adaptive optics for free space optical communications

Andrew Reeves, Nancy Ageorges, Dirk Kampf, Dailos Guerra Ramos, Mohamad Abdo, Ilija Hristovski, Helawae Friew Kelemu, Douglas Laidlaw, Zoran Sodnik, Ramon Mata Calvo, Bruno Femenía-Castellá

Proceedings Volume 12877, 128771S (2024) https://doi.org/10.1117/12.3002594

KEYWORDS: Wavefront sensors, Near infrared, Adaptive optics, Satellites, Beam path, Design, Sensors, Cameras, Telescopes, Sodium

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Proceedings Article | 27 July 2018 Paper

Paper

The MICADO first light imager for ELT: cold optics instrument

J. Schubert, M. Hartl, V. Hörmann, R. Davis, E. Sturm, N. Ageorges, L. Barl, V. Garrel, N. Geis, H. Gemperlein, D. Kampf, C. Mandla, M. Manhart, S. Rabien, R. Rüddenklau, J. Ziegleder

Proceedings Volume 10702, 107028W (2018) https://doi.org/10.1117/12.2311867

KEYWORDS: Mirrors, Adaptive optics, Imaging systems, Relays, Spectroscopy, Calibration, Optical design, Zoom lenses, Telescopes, Cameras

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Proceedings Article | 6 July 2018 Presentation + Paper

Presentation + Paper

NEAR: new earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)

Hans-Ulrich Käufl, Markus Kasper, Robin Arsenault, Gerd Jakob, Serban Leveratto, Gerard Zins, Eloy Fuenteseca, Miguel Riquelme, Ralf Siebenmorgen, Michael Sterzik, Nancy Ageorges, Sven Gutruf, Dirk Kampf, Arnd Reutlinger, Olivier Absil, Brunella Carlomagno, Olivier Guyon, Pete Klupar, Dimitri Mawet, Garreth Ruane, Mikael Karlsson, Eric Pantin, Kjetil Dohlen

Proceedings Volume 10702, 107020D (2018) https://doi.org/10.1117/12.2313395

KEYWORDS: Coronagraphy, Telescopes, Stars, Adaptive optics, Sensors, Mirrors, Planets, Optical filters

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Proceedings Article | 22 July 2014 Paper

Paper

Commissioning and science verification of the 2m-Fraunhofer Wendelstein Telescope

Ulrich Hopp, Ralf Bender, Frank Grupp, Claus Goessl, Florian Lang-Bardl, Wolfgang Mitsch, Arno Riffeser, Nancy Ageorges

Proceedings Volume 9145, 91452D (2014) https://doi.org/10.1117/12.2054498

KEYWORDS: Telescopes, Mirrors, Space telescopes, Observatories, Charge-coupled devices, Point spread functions, Stars, Spectrographs, CCD cameras, Cameras

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Proceedings Article | 24 September 2012 Open Access

Open Access

Paper

LUCI in the sky: performance and lessons learned in the first two years of near-infrared multi-object spectroscopy at the LBT

Peter Buschkamp, Walter Seifert, Kai Polsterer, Reiner Hofmann, Hans Gemperlein, Reinhard Lederer, Michael Lehmitz, Vianak Naranjo, Nancy Ageorges, Jaron Kurk, Frank Eisenhauer, Sebastian Rabien, Mathias Honsberg, Reinhard Genzel

Proceedings Volume 8446, 84465L (2012) https://doi.org/10.1117/12.926989

KEYWORDS: Sensors, Imaging spectroscopy, Adaptive optics, Cameras, Molybdenum, Spectroscopy, Switches, Astronomical imaging, Spectroscopes, Imaging systems

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Proceedings Article | 17 September 2012 Paper

Paper

First tests of the compact low scattered-light 2m-Wendelstein Fraunhofer Telescope

Ulrich Hopp, Ralf Bender, Frank Grupp, Hans Thiele, Nancy Ageorges, Peter Aniol, Heinz Barwig, Claus Gössl, Florian Lang-Bardl, Wolfgang Mitsch, Michael Ruder

Proceedings Volume 8444, 84442V (2012) https://doi.org/10.1117/12.926427

KEYWORDS: Telescopes, Observatories, Mirrors, Space telescopes, Domes, Reflectivity, Imaging systems, Coating, Astronomical telescopes, Cameras

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Proceedings Article | 17 September 2012 Paper

Paper

New Fraunhofer Telescope Wendelstein: assembly, installation, and current status

Hans Thiele, Nancy Ageorges, Dirk Kampf, Mike Hartl, Sebastian Egner, Peter Aniol, Micheal Ruder, Christian Abfalter, Ulrich Hopp, Ralf Bender, Claus Gössl, Frank Grupp, Florian Lang-Bardl, Wolfgang Mitsch

Proceedings Volume 8444, 84441B (2012) https://doi.org/10.1117/12.927096

KEYWORDS: Telescopes, Mirrors, Domes, Space telescopes, Observatories, Optical fabrication, Electronics, Image quality, Integrated optics, Optical alignment

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Proceedings Article | 25 August 2010 Paper

Paper

LUCIFER1: performance results

Walter Seifert, Nancy Ageorges, Michael Lehmitz, Peter Buschkamp, Volker Knierim, Kai Polsterer, Andre Germeroth, Anna Pasquali, Vianak Naranjo, Marcus Jütte, Carmen Feiz, Hans Gemperlein, Reiner Hofmann, Werner Laun, Reinhard Lederer, Rainer Lenzen, Ulrich Mall, Holger Mandel, Peter Müller, Andreas Quirrenbach, Ludwig Schäffner, Clemens Storz, Peter Weiser

Proceedings Volume 7735, 77357W (2010) https://doi.org/10.1117/12.857782

KEYWORDS: Cameras, Sensors, Imaging spectroscopy, Image quality, Distortion, Molybdenum, Spectroscopes, Telescopes, Mirrors, Calibration

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Proceedings Article | 28 July 2010 Open Access

Open Access

Paper

ARGOS: the laser guide star system for the LBT

S. Rabien, N. Ageorges, L. Barl, U. Beckmann, T. Blümchen, M. Bonaglia, J. Borelli, J. Brynnel, L. Busoni, L. Carbonaro, R. Davies, M. Deysenroth, O. Durney, M. Elberich, S. Esposito, V. Gasho, W. Gässler, H. Gemperlein, R. Genzel, R. Green, M. Haug, M. Hart, P. Hubbard, S. Kanneganti, E. Masciadri, J. Noenickx, G. Orban de Xivry, D. Peter, A. Quirrenbach, M. Rademacher, H. Rix, P. Salinari, C. Schwab, J. Storm, L. Strüder, M. Thiel, G. Weigelt, J. Ziegleder

Proceedings Volume 7736, 77360E (2010) https://doi.org/10.1117/12.857210

KEYWORDS: Adaptive optics, Mirrors, Stars, Laser systems engineering, Wavefront sensors, Sensors, Laser guide stars, Telescopes, Calibration, Turbulence

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Proceedings Article | 21 July 2010 Open Access

Open Access

Paper

The LUCIFER MOS: a full cryogenic mask handling unit for a near-infrared multi-object spectrograph

Peter Buschkamp, Reiner Hofmann, Hans Gemperlein, Kai Polsterer, Nancy Ageorges, Frank Eisenhauer, Reinhard Lederer, Mathias Honsberg, Marcus Haug, Johann Eibl, Walter Seifert, Reinhard Genzel

Proceedings Volume 7735, 773579 (2010) https://doi.org/10.1117/12.857950

KEYWORDS: Molybdenum, Cryogenics, Switches, Control systems, Telescopes, Astronomical imaging, Spectrographs, Electronics, Camera shutters, Head

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Proceedings Article | 19 July 2010 Paper

Paper

The LUCIFER control software

Marcus Jütte, Volker Knierim, Kai Polsterer, Michael Lehmitz, Clemens Storz, Walter Seifert, Nancy Ageorges

Proceedings Volume 7740, 774004 (2010) https://doi.org/10.1117/12.857022

KEYWORDS: Molybdenum, Telescopes, Software development, Computer architecture, Mirrors, Control systems, Human-machine interfaces, Java, Cameras, Imaging spectroscopy

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Proceedings Article | 15 July 2010 Open Access

Open Access

Paper

MICADO: the E-ELT adaptive optics imaging camera

Richard Davies, N. Ageorges, L. Barl, L. Bedin, R. Bender, P. Bernardi, F. Chapron, Y. Clenet, A. Deep, E. Deul, M. Drost, F. Eisenhauer, R. Falomo, G. Fiorentino, N. Förster Schreiber, E. Gendron, R. Genzel, D. Gratadour, L. Greggio, F. Grupp, E. Held, T. Herbst, H.-J. Hess, Z. Hubert, K. Jahnke, K. Kuijken, D. Lutz, D. Magrin, B. Muschielok, R. Navarro, E. Noyola, T. Paumard, G. Piotto, R. Ragazzoni, A. Renzini, G. Rousset, H.-W. Rix, R. Saglia, L. Tacconi, M. Thiel, E. Tolstoy, S. Trippe, N. Tromp, E. Valentijn, G. Verdoes Kleijn, M. Wegner

Proceedings Volume 7735, 77352A (2010) https://doi.org/10.1117/12.856379

KEYWORDS: Adaptive optics, Calibration, Stars, Sensors, Mirrors, Point spread functions, Optical filters, Imaging spectroscopy, Cameras, Galactic astronomy

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Proceedings Article | 15 July 2010 Paper

Paper

LUCIFER1 commissioning at the LBT

N. Ageorges, W. Seifert, M. Jütte, V. Knierim, M. Lehmitz, A. Germeroth, P. Buschkamp, K. Polsterer, A. Pasquali, V. Naranjo, H. Gemperlein, J. Hill, C. Feiz, R. Hofmann, W. Laun, R. Lederer, R. Lenzen, U. Mall, H. Mandel, P. Müller, A. Quirrenbach, L. Schäffner, C. Storz, P. Weiser

Proceedings Volume 7735, 77351L (2010) https://doi.org/10.1117/12.857760

KEYWORDS: Stars, Cameras, Telescopes, Electroluminescent displays, Molybdenum, Spectroscopy, Sensors, Imaging spectroscopy, Image quality, Calibration

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Proceedings Article | 16 July 2008 Paper

Paper

Tests of the PSF reconstruction algorithm for NACO/VLT

Yann Clénet, Christopher Lidman, Eric Gendron, Gérard Rousset, Thierry Fusco, Nick Kornweibel, Markus Kasper, Nancy Ageorges

Proceedings Volume 7015, 701529 (2008) https://doi.org/10.1117/12.789395

KEYWORDS: Point spread functions, Reconstruction algorithms, Adaptive optics, Calibration, Optical transfer functions, Algorithm development, Space telescopes, Stars, Telescopes, Device simulation

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Proceedings Article | 11 July 2008 Paper

Paper

LUCIFER status report: summer 2008

Holger Mandel, Walter Seifert, Reiner Hofmann, Marcus Jütte, Rainer Lenzen, Nancy Ageorges, Dominik Bomans, Peter Buschkamp, Ralf-Jürgen Dettmar, Carmen Feiz, Hans Gemperlein, André Germeroth, Lutz Geuer, Jochen Heidt, Volker Knierim, Werner Laun, Michael Lehmitz, Ulrich Mall, Peter Müller, Vianac Naranjo, Kai Polsterer, Andreas Quirrenbach, Ludwig Schäffner, Florian Schwind, Peter Weiser, Harald Weisz

Proceedings Volume 7014, 70143S (2008) https://doi.org/10.1117/12.787203

KEYWORDS: Molybdenum, Imaging spectroscopy, Telescopes, Cameras, Spectroscopes, Diffraction, Astronomical imaging, Software development, Mirrors, Control systems

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Proceedings Article | 9 July 2008 Paper

Paper

Performance of HAWK-I: the new high acuity wide-field K-band imager

M. Kissler-Patig, N. Ageorges, C. Alves de Oliveira, L. Bedin, E. Bendek, M. Casali, R. Dorn, R. Esteves, G. Finger, D. Gojak, Y. Jung, M. Kiekebusch, A. Moorwood, J.-L. Lizon, M. Petr-Gotzens, J. F. Pirard, J. Pritchard, F. Selman

Proceedings Volume 7014, 70140Q (2008) https://doi.org/10.1117/12.787009

KEYWORDS: Sensors, Stars, Image quality, Imaging systems, Distortion, Optical filters, Calibration, Telescopes, K band, Nondestructive evaluation

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Proceedings Article | 7 July 2008 Open Access

Open Access

Paper

The laser guide star program for the LBT

S. Rabien, N. Ageorges, R. Angel, G. Brusa, J. Brynnel, L. Busoni, R. Davies, M. Deysenroth, S. Esposito, W. Gässler, R. Genzel, R. Green, M. Haug, M. Lloyd Hart, G. Hölzl, E. Masciadri, R. Pogge, A. Quirrenbach, M. Rademacher, H. W. Rix, P. Salinari, C. Schwab, T. Stalcup, J. Storm, L. Strüder, M. Thiel, G. Weigelt, J. Ziegleder

Proceedings Volume 7015, 701515 (2008) https://doi.org/10.1117/12.788173

KEYWORDS: Adaptive optics, Telescopes, Stars, Laser guide stars, Wavefront sensors, Laser systems engineering, Sensors, Space telescopes, Mirrors, Diffraction

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Proceedings Article | 28 June 2006 Paper

Paper

PSF reconstruction for NAOS-CONICA

Yann Clénet, Markus Kasper, Eric Gendron, Thierry Fusco, Gérard Rousset, Damien Gratadour, Christopher Lidman, Olivier Marco, Nancy Ageorges, Sebastian Egner

Proceedings Volume 6272, 62723T (2006) https://doi.org/10.1117/12.673901

KEYWORDS: Point spread functions, Optical transfer functions, Reconstruction algorithms, Adaptive optics, Algorithm development, Computer simulations, Error analysis, Mirrors, Statistical analysis, Stars

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Proceedings Article | 25 October 2004 Paper

Paper

Study of atmospheric sodium above Chile

Nancy Ageorges, Sebastian Els

Proceedings Volume 5490, (2004) https://doi.org/10.1117/12.549315

KEYWORDS: Sodium, Atmospheric monitoring, Atmospheric optics, Adaptive optics, Observatories, Laser guide stars

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Proceedings Article | 25 October 2004 Paper

Paper

NAOS performance characterization and turbulence parameters estimation using closed-loop data

Thierry Fusco, Nancy Ageorges, Gerard Rousset, Didier Rabaud, Eric Gendron, David Mouillet, Francois Lacombe, Gerard Zins, Julien Charton, Christopher Lidman, Norbert Hubin

Proceedings Volume 5490, (2004) https://doi.org/10.1117/12.563009

KEYWORDS: Adaptive optics, Turbulence, Telescopes, Real-time computing, Stars, Data analysis, Computing systems, Error analysis, Signal to noise ratio, Large telescopes

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Proceedings Article | 25 October 2004 Paper

Paper

NACO performance: status after 2 years of operation

Yann Clenet, Markus Kasper, Nancy Ageorges, Christopher Lidman, Thierry Fusco, Olivier Marco, Markus Hartung, David Mouillet, Bertrand Koehler, Gerard Rousset, Norbert Hubin

Proceedings Volume 5490, (2004) https://doi.org/10.1117/12.551148

KEYWORDS: Telescopes, Adaptive optics, Turbulence, Current controlled current source, Infrared imaging, Infrared radiation, Device simulation, Infrared telescopes, Image quality, Calibration

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Proceedings Article | 30 September 2004 Paper

Paper

Commissioning of the NACO Fabry-Perot interferometer at the VLT

Markus Hartung, Chris Lidman, Nancy Ageorges, Olivier Marco, Markus Kasper, Yann Clenet

Proceedings Volume 5492, (2004) https://doi.org/10.1117/12.552048

KEYWORDS: Calibration, Phase shifts, Adaptive optics, Fabry–Perot interferometry, Imaging spectroscopy, Cameras, Argon, Spectroscopes, Tunable filters, Astronomy

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Proceedings Article | 16 September 2004 Paper

Paper

Quality control of VLT NACO data

Danuta Dobrzycka, Wolfgang Hummel, Chris Lidman, Nancy Ageorges, Olivier Marco, Yves Jung

Proceedings Volume 5493, (2004) https://doi.org/10.1117/12.551147

KEYWORDS: Adaptive optics, Calibration, Lamps, Infrared telescopes, Infrared cameras, Infrared imaging, Cameras, Process control, Data processing, Imaging systems

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Proceedings Article | 14 February 2003 Paper

Paper

Linear and circular polarization studies of the Eta Carinae Homunculus nebula

Jeremy Walsh, Nancy Ageorges

Proceedings Volume 4843, (2003) https://doi.org/10.1117/12.458622

KEYWORDS: Polarization, Scattering, Stars, Polarimetry, Wave plates, Rayleigh scattering, Multiple scattering, Linear filtering, Clouds, Silicates

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Proceedings Article | 14 February 2003 Paper

Paper

Polarimetry with adaptive optics at ESO Very Large Telescope (Yepun)

Nancy Ageorges, Rainer Lenzen, Markus Hartung, Wolfgang Brandner, Eric Gendron, Alan Moorwood, Anne-Marie Lagrange

Proceedings Volume 4843, (2003) https://doi.org/10.1117/12.459344

KEYWORDS: Polarization, Polarimetry, Prisms, Adaptive optics, Telescopes, Calibration, Infrared radiation, Polarizers, Infrared telescopes, Infrared cameras

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Proceedings Article | 7 February 2003 Paper

Paper

VLT laser guide star monitor facility: a feasibility study

Fernando Pedichini, Nancy Ageorges, Marc Sarazin

Proceedings Volume 4839, (2003) https://doi.org/10.1117/12.460056

KEYWORDS: Sodium, Telescopes, Stars, Laser guide stars, Adaptive optics, Lanthanum, Sensors, Cameras, Image processing, Meteorology

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Proceedings Article | 17 November 2000 Paper

Paper

ELP-OA: measuring the wavefront tilt without a natural guide star

Matthias Schoeck, Jean-Paul Pique, Alain Petit, Patrick Chevrou, Vincent Michau, Gilbert Grynberg, Arnold Migus, Nancy Ageorges, Veronique Bellanger, Francois Biraben, Ruy Deron, Hayden Fews, Francoise-Claude Foy, Claudia Hoegemann, Markus Laubscher, Daniel Mueller, Celine d'Orgeville, Olivier Peillet, Mike Redfern, Renaud Foy, Patricia Segonds, Richard Soden, Michel Tallon, Eric Thiebaut, Andrei Tokovinin, Jerome Vaillant, Jean-Marc Weulersse

Proceedings Volume 4125, (2000) https://doi.org/10.1117/12.409304

KEYWORDS: Telescopes, Stars, Sodium, Wavefronts, Adaptive optics, Modulation, Laser guide stars, Oscillators, Astronomy, Chemical species

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Proceedings Article | 16 August 2000 Paper

Paper

Polychromatic guide star: feasibility study

Renaud Foy, Jean-Paul Pique, Alain Petit, Patrick Chevrou, Vincent Michau, Gilbert Grynberg, Arnold Migus, Nancy Ageorges, Veronique Bellanger, Francois Biraben, Ruy Deron, Hayden Fews, Francoise-Claude Foy, Claudia Hoegemann, Markus Laubscher, Daniel Mueller, Celine d'Orgeville, Olivier Peillet, Mike Redfern, Matthias Schoeck, Patricia Segonds, Richard Soden, Michel Tallon, Eric Thiebaut, Andrei Tokovinin, Jerome Vaillant, Jean-Marc Weulersse

Proceedings Volume 4065, (2000) https://doi.org/10.1117/12.407359

KEYWORDS: Telescopes, Sodium, Stars, Oscillators, Adaptive optics, Modulation, Wavefronts, Chemical species, Photons, Laser guide stars

Read Abstract +

Adaptive optics at astronomical telescopes aims at correcting in real time the phase corrugations of incoming wavefronts caused by the turbulent atmosphere, as early proposed by Babcock. Measuring the phase errors requires a bright source located within the isoplanatic patch of the program source. The probability that such a reference source exists is a function of the wavelength, of the required image quality (Strehl ratio), of the turbulence optical properties, and of the direction of the observation. It turns out that the sky coverage is disastrously low in particular in the visible wavelength range where, unfortunately, the gain in spatial resolution brought by adaptive optics is the largest. Foy and Labeyrie have proposed to overcome this difficulty by creating an artificial point source in the sky in the direction of the observation relying on the backscattered light due to a laser beam. This laser guide star (hereinafter referred to as LGS) can be bright enough to allow us to accurately measure the wavefront phase errors, except for two modes which are the piston (not relevant in this case) and the tilt. Pilkington has emphasized that the round trip time of the laser beam to the mesosphere, where the LGS is most often formed, is significantly shorter than the typical tilt coherence time; then the inverse-return-of-light principle causes deflections of the outgoing and the ingoing beams to cancel. The apparent direction of the LGS is independent of the tilt. Therefore the tilt cannot be measured only from the LGS. Until now, the way to overcome this difficulty has been to use a natural guide star to sense the tilt. Although the tilt is sensed through the entire telescope pupil, one cannot use a faint source because $APEX 90% of the variance of the phase error is in the tilt. Therefore, correcting the tilt requires a higher accuracy of the measurements than for higher orders of the wavefront. Hence current adaptive optics devices coupled with a LGS face low sky coverage. Several methods have been proposed to get a partial sky coverage for the tilt. The only one providing us with a full sky coverage is the polychromatic LGS (hereafter referred to as PLGS). We present here a progress report of the R&D program Etoile Laser Polychromatique et Optique Adaptative (ELP-OA) carried out in France to develop the PLGS concept. After a short recall of the principles of the PLGS, we will review the goal of ELP-OA and the steps to get over to bring it into play. We finally shortly described the effort in Europe to develop the LGS.

Proceedings Article | 7 July 2000 Paper

Paper

PASS-2: quantitative photometric measurements of the polychromatic laser guide star

Matthias Schoeck, Renaud Foy, Jean-Paul Pique, Patrick Chevrou, Nancy Ageorges, Alain Petit, Veronique Bellanger, Hayden Fews, Francoise-Claude Foy, Claudia Hoegemann, Markus Laubscher, Olivier Peillet, Patricia Segonds, Michel Tallon, Jean-Marc Weulersse

Proceedings Volume 4007, (2000) https://doi.org/10.1117/12.390338

KEYWORDS: Laser guide stars, Telescopes, Sodium, Stars, Global system for mobile communications, Oscillators, Wavefronts, Adaptive optics, Calibration, Photometry

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Proceedings Article | 7 July 2000 Paper

Paper

ELPOA: toward the tilt measurement from a polychromatic laser guide star

Renaud Foy, Jean-Paul Pique, Alain Petit, Patrick Chevrou, Vincent Michau, Gilbert Grynberg, Arnold Migus, Nancy Ageorges, Veronique Bellanger, Francois Biraben, Ruy Deron, Hayden Fews, Francoise-Claude Foy, Claudia Hoegemann, Markus Laubscher, Daniel Mueller, Celine d'Orgeville, Olivier Peillet, Mike Redfern, Matthias Schoeck, Patricia Segonds, Richard Soden, Michel Tallon, Eric Thiebaut, Andrei Tokovinin, Jerome Vaillant, Jean-Marc Weulersse

Proceedings Volume 4007, (2000) https://doi.org/10.1117/12.390401

KEYWORDS: Telescopes, Sodium, Oscillators, Adaptive optics, Modulation, Laser guide stars, Photons, Chemical species, Wavefronts, Atmospheric optics

Read Abstract +

Adaptive optics at astronomical telescopes aims at correcting in real time the phase corrugations of incoming wavefronts caused by the turbulent atmosphere, as early proposed by Babcock. Measuring the phase errors requires a bright source, which is located within the isoplanatic patch of the program source. The probability that such a reference source exists is a function of the wavelength of the observation, of the required image quality (Strehl ratio), of the turbulence optical properties, and of the direction of the observation. Several papers have addressed the problem of the sky coverage as a function of these parameters (see e.g.: Le Louarn et al). It turns out that the sky coverage is disastrously low in particular in the short (visible) wavelength range where, unfortunately, the gain in spatial resolution brought by adaptive optics is the largest. Foy and Labeyrie have proposed to overcome this difficulty by creating an artificial point source in the sky in the direction of the observation relying on the backscattered light due to a laser beam. This laser guide star (hereafter referred to as LGS) can be bright enough to allow us to accurately measure the wavefront phase errors, except for two modes which are the piston (which is not relevant in this case) and the tilt. Pilkington has emphasized that the round trip time of the laser beam to the mesosphere, where the LGS is most often formed, is significantly shorter than the typical tilt coherence time; then the inverse-return- of-light principle causes deflections of the outgoing and the ingoing beams to cancel. The apparent direction of the LGS is independent of the tilt. Therefore the tilt cannot be measured only from the LGS. Until now, the way to overcome this difficulty has been to use a natural guide star to sense the tilt. Although the tilt is sensed through the entire telescope pupil, one cannot use a faint source because approximately equals 90% of the variance of the phase error is in the tilt. Therefore, correcting the tilt requires a higher accuracy of the measurements than for higher orders of the wavefront. Hence current adaptive optics devices coupled with a LGS face low sky coverage. Several methods have been proposed to get a partial or total sky coverage for the tilt, such as the dual adaptive optics concept, the elongation perspective method, or the polychromatic LGS (hereafter referred to as PLGS). We present here a progress report of the R&D program Etoile Laser Polychromatique et Optique Adaptative (ELP-OA) carried out in France to develop the PLGS concept. After a short recall of the principles of the PLGS, we will review the goal of ELP-OA and the steps to get over to bring it into play.

Proceedings Article | 7 July 2000 Paper

Paper

Sodium layer monitoring at Calar Alto by LIDAR

David Butler, Richard Davies, Hayden Fews, R. Michael Redfern, Nancy Ageorges, Wolfgang Hackenberg, Ralf-Rainer Rohloff, Sebastian Rabien, Thomas Ott, Stefan Hippler

Proceedings Volume 4007, (2000) https://doi.org/10.1117/12.390318

KEYWORDS: Sodium, Telescopes, LIDAR, Avalanche photodetectors, Photons, Pulsed laser operation, Laser guide stars, Calibration, Adaptive optics, Sensors

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Observations have shown the presence of sodium layer centroid height variations of a few hundred meters on timescales of tens of seconds. As quality laser guide star (LGS) plus adaptive optics (AO) assisted astronomy, especially on large (8m+) telescopes, will require optimal scheduling of observations and regular laser and wavefront sensor focusing at sites where sporadic sodium layers are frequent, an 'easy to use' sodium layer monitor is required. LIDAR offers a convenient means to achieve this. By pulsing the outgoing sodium laser and performing time-of-flight measurements on the returned photons we can acquire the altitude profile of the sodium layer. Unfortunately, conventional LIDAR requires the laser duty cycle to be very low, therefore large integration times are required. However, by using a cross-correlation technique the duty cycle can be increased to 50%, which gives far better performance. We present the details of this technique which involved amplitude modulation of the MPIA/MPE ALFA cw laser, as well as the following results of such LIDAR measurements performed in October 1999 at the 3.5 m telescope at Calar Alto Observatory in Spain. The altitude of the sodium layer at Calar Alto on 17th and 18th October 1999 was found to be at 90 +/- 3 km and there is evidence for sporadics on one of two nights with sporadic layer FWHM* varying from approximately 240 to 350 m. In addition, a noticeable layer FWHM change (excluding the sporadic layer) from approximately 13 to approximately 5 - 7 km was observed over the two nights. After flux and altitude calibration and correction of the projected altitude range, a very good agreement is found between sodium layer profiles derived from an auxiliary telescope and 3.5 m telescope LIDAR observations. Using an intensity weighted centroid algorithm the centroid height of the sodium layer was observed to have a variation of < 500 m in approximately 10 minutes. Although, shorter timescale variations may be have been present, poor observing conditions and resulting reduced S/N prevents this analysis.

Proceedings Article | 7 July 2000 Paper

Paper

Laser guide star: monitoring and light pollution

Nancy Ageorges, R. Michael Redfern, Francoise Delplancke, Creidhe O'Sullivan

Proceedings Volume 4007, (2000) https://doi.org/10.1117/12.390336

KEYWORDS: Sodium, Telescopes, Laser guide stars, Adaptive optics, Pollution, Laser scattering, Scattering, Atmospheric optics, Light scattering, Rayleigh scattering

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Proceedings Article | 5 October 1999 Paper

Paper

Monitoring of laser guide star and light pollution

Nancy Ageorges, Francoise Delplancke, Norbert Hubin, Richard Davies

Proceedings Volume 3763, (1999) https://doi.org/10.1117/12.363626

KEYWORDS: Telescopes, Sodium, Laser guide stars, Laser scattering, Rayleigh scattering, Light scattering, Atmospheric particles, Pollution, Atmospheric modeling, Mie scattering

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Proceedings Article | 27 September 1999 Paper

Paper

LGS Na spot elongation and Rayleigh scattering effects on Shack-Hartmann wavefront sensor performances

Elise Vernet-Viard, Francoise Delplancke, Norbert Hubin, Nancy Ageorges

Proceedings Volume 3762, (1999) https://doi.org/10.1117/12.363578

KEYWORDS: Telescopes, Rayleigh scattering, Sodium, Atmospheric modeling, Laser scattering, Wavefront sensors, Adaptive optics, Sensors, Laser guide stars, Stars

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Proceedings Article | 11 September 1998 Paper

Paper

Polarimetric adaptive optics data of eta Carinae and the Homunculus nebula

Nancy Ageorges, Jeremy Walsh

Proceedings Volume 3353, (1998) https://doi.org/10.1117/12.321739

KEYWORDS: Polarization, Adaptive optics, Calibration, Polarizers, Polarimetry, Data acquisition, Point spread functions, Scattering, Stars, K band

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Proceedings Article | 11 September 1998 Paper

Paper

Deconvolution of ADONIS images

Julian Christou, Franck Marchis, Nancy Ageorges, Domenico Bonaccini, Francois Rigaut

Proceedings Volume 3353, (1998) https://doi.org/10.1117/12.321719

KEYWORDS: Point spread functions, Deconvolution, Stars, Observatories, Adaptive optics, Imaging systems, Diffraction, Thermography, Image processing, Satellites

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Proceedings Article | 17 October 1997 Paper

Paper

Deconvolution of adaptive optics near-infrared system (ADONIS) images

Julian Christou, Domenico Bonaccini, Nancy Ageorges

Proceedings Volume 3126, (1997) https://doi.org/10.1117/12.279065

KEYWORDS: Point spread functions, Deconvolution, Adaptive optics, Signal to noise ratio, Stars, Speckle, Observatories, Error analysis, K band, Calibration

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Showing 5 of 39 publications

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