Lothar Noethe - Academia.edu (original) (raw)

Papers by Lothar Noethe

Research paper thumbnail of Book review: Reflecting telescope optics II, by Ray Wilson

The Messenger, Nov 29, 2001

Research paper thumbnail of Active optics in modern large optical telescopes

Research paper thumbnail of Use of Minimum-energy Modes for Modal-active Optics Corrections of Thin Meniscus Mirrors

Journal of Modern Optics, 1991

Abstract For thin meniscus mirrors the modes which correct arbitrary wave-front aberrations in th... more Abstract For thin meniscus mirrors the modes which correct arbitrary wave-front aberrations in the most efficient way are derived. These modes are similar to the free-vibration modes of the mirror. The relationship between the two types of modes is shown. The most important features such as orthogonality and energy of the modes are discussed. This modal approach is applied to a few practical problems in connection with the primary mirrors of the Very Large Telescope of the European Southern Observatory.

Research paper thumbnail of Towards Fully Automated Optimisation of Optical Quality in Telescopes

Research paper thumbnail of Active optics: the NTT and the future

Research paper thumbnail of Performance of spatial filtering wavefront sensor for the phasing of segmented telescopes

The next generation of extremely large telescopes requires the use of segmented mirrors. This tec... more The next generation of extremely large telescopes requires the use of segmented mirrors. This technology needs specific wave front sensors to measure the alignment and phasing state. This paper compares two specific technologies for the measurement of wavefront steps between segments: a simple pin hole and a phase contrast sensor. The efficiency of each sensor will be quantified by calculating the Fisher information, first, under ideal conditions, then including the effects of sampling and atmospheric turbulence.

Research paper thumbnail of Optical analysis of thermally cycled 515 mm metallic Al/Al-alloy mirrors

Astronomy and Astrophysics, 1986

Research paper thumbnail of Phasing segmented deformable mirrors with the Zernike phase contrast method

Astronomical Telescopes and Instrumentation, 2012

Research paper thumbnail of Optical Wavefront Analysis of Thermally Cycled 500 mm Metallic Mirrors

International Astronomical Union Colloquium, 1984

Warping is a major concern in the use of aluminium as a material for large mirrors. The warping c... more Warping is a major concern in the use of aluminium as a material for large mirrors. The warping characteristics are influenced by:*the type of material, i.e. pure aluminium or some alloy*the type of fabrication, i.e. cast, rolled or forged.So far there is little data available on the warping characteristics of aluminium mirrors. Therefore ESO has tested the warping behaviour of 18 aluminium mirrors under thermal cycling conditions with a glass ceramic mirror, which has not been cycled, as a reference mirror. The set of 500 mm mirrors selected for this experiment is described in [1].

Research paper thumbnail of From Passive Support Systems to the NTT Active Support

International Astronomical Union Colloquium, 1984

ESO has two telescope projects: the NTT (New Technology Telescope) with 3.5 m aperture and the VL... more ESO has two telescope projects: the NTT (New Technology Telescope) with 3.5 m aperture and the VLT (Very Large Telescope) with 16 m equivalent aperture. The former is already in the engineering phase and should be completed in 1987; the latter is still in the study phase and will be described at this conference by our colleague, D. Enard.This paper is concerned with the primary support system of the NTT. The basic principles and layout of this support have already been described in the literature 1,2,3).

Research paper thumbnail of Focal-plane wavefront sensing for active optics in the VST based on an analytical optical aberration model

Ground-based and Airborne Telescopes VI, 2016

We study a novel focal plane wavefront sensing and active optics control scheme at the VST on Cer... more We study a novel focal plane wavefront sensing and active optics control scheme at the VST on Cerro Paranal, an f /5.5 survey telescope with a 1Ö1 degree field of view and a 2.6 m primary mirror. This scheme analyzes the elongation pattern of stellar PSFs across the full science image (256 Mpixels) and compares their second moments with an analytical model based on 5th-order geometrical optics. We consider 11 scalar degrees of freedom in mirror misalignments and deformations (M2 piston, tip/tilt and lateral displacement, detector tip/tilt, plus M1 figure astigmatism and trefoil). Using a numerical optimization method, we extract up to 4000 stars and complete the fitting process in under one minute. We demonstrate successful closed-loop active optics control based on maximum likelihood filtering.

Research paper thumbnail of ESO VLT - Primary Mirror Support System

Research paper thumbnail of Towards establishing specifications for large telescopes optics

Very Large Telescopes and Their Instrumentation Vol 1, 1988

Research paper thumbnail of Active optics system of the VLT Survey Telescope

Applied Optics, 2016

This paper describes the active optics system of the VST (VLT Survey Telescope), the 2.6-m survey... more This paper describes the active optics system of the VST (VLT Survey Telescope), the 2.6-m survey telescope designed for visible wavelengths of the European Southern Observatory at Cerro Paranal, in the Atacama desert. The telescope is characterized by a wide field of view (1.42 degree diameter), leading to tighter active optics than in conventional telescopes, in particular for the alignment requirements. We discuss the effects of typical error sources on the image quality and present the specific solutions adopted for wavefront sensing and correction of the aberrations, which are based on the shaping of a monolithic primary mirror and the positioning of the secondary in 5 degrees of freedom.

Research paper thumbnail of Closed-Loop Active Optics: Its Advantages And Limitations For Correction Of Wind-Buffet Deformations Of Large Flexible Mirrors

SPIE Proceedings, 1989

Wind buffet deformation of large flexible mirrors is, from its frequency bandpass and other chara... more Wind buffet deformation of large flexible mirrors is, from its frequency bandpass and other characteristics, an overlap area between normal low bandpass "Active Optics" and high bandpass "Adaptive Optics". The fundamental problem posed is that the time frequencies involved do not permit the elimination of external seeing effects by appropriate time integrations with the image analyser, as in normal low bandpass closed-loop operation. Confusion between the wind deformation and atmospheric functions results. For wind buffet correction in these circumstances, we analyse the possibilities and limitations of the closed-loop principle using one or more image analysers in a number of configurations. Some important parameters of the atmospheric function apear to be insufficiently known and should be measured experimentally if rapid practical progress is to be made. Cross-checks betweens closed-loop and open-loop methods in a two-pronged approach seem highly desirable.

Research paper thumbnail of <title>Exploring model based engineering for large telescopes: getting started with descriptive models</title>

Modeling, Systems Engineering, and Project Management for Astronomy III, 2008

This paper was (will be) published in Proceedings of SPIE Astronomical Telescopes and Instrumenta... more This paper was (will be) published in Proceedings of SPIE Astronomical Telescopes and Instrumentation 2008 and is made available as an electronic reprint (preprint) with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Research paper thumbnail of <title>Measurements of the isoplanatic angle of image motion for angular separations up to 10 arcmin</title>

Advanced Technology Optical Telescopes V, 1994

Star trails have been taken with a CCD-camera covering a field of approximately 10'. With the... more Star trails have been taken with a CCD-camera covering a field of approximately 10'. With the telescope movement stopped the sampling rate was of the order of 40 Hz. The correlations between the centroid variations of different trails, representing the image motion perpendicular to the trails, have been calculated. The power spectra of the centroid motions are used to identify their origin. The method turns out to be feasible for the measurement of the isoplanatic angle of image motion. The results show that the correlations of the image motions can be significantly enhanced, if the time delay due to the movement of the turbulence across the field of the telescope is taken into account.

Research paper thumbnail of Retrofitting New Technology to an Old Telescope

Research paper thumbnail of <title>Disentangling between low order telescope aberrations and segmentation errors using a Shack-Hartmann sensor</title>

Ground-based and Airborne Telescopes II, 2008

ABSTRACT The shape correction of the mirrors is a crucial operation to obtain diffraction limited... more ABSTRACT The shape correction of the mirrors is a crucial operation to obtain diffraction limited images in actively controlled telescopes. If the mirror is not monolithic, the segmentation errors introduced by piston, tip and tilt of the segments are superimposed on the continuous aberrations. In the case of a sensor based on the measurement of the wave front slopes, like the Shack-Hartmann wave front sensor, an algorithm which allows separating the different contributions is necessary for a proper correction. In the framework of the Active Phasing Experiment (APE) carried out at ESO, we have developed a simple algorithm which can be applied to compute the aberrations and the tip-tilt coefficients using the information obtained with a Shack-Hartmann sensor. It is based on the construction of an orthogonal base in the space of the wave front slope functions. The description of the algorithm and its performance in the cases of low-order aberrations superimposed on tip-tilt misalignment of the segments are reported. A particular application of this technique in the case of the European Extremely Large Telescope (E-ELT) is discussed and the expected upper limits for the residual errors after correction are estimated.

Research paper thumbnail of The First Active Segmented Mirror at ESO

The Active Phasing Experiment (APE) is part of the Extremely Large Telescope Design Study which i... more The Active Phasing Experiment (APE) is part of the Extremely Large Telescope Design Study which is supported by the European Framework Programme 6. This experiment, which is conducted in collaboration with several partners is a demonstrator to test and qualify newly-developed phasing sensors for the alignment of segmented mirrors and test the phasing software within a telescope control system to be developed for a future European Extremely Large Telescope. The segmentation of a primary mirror is simulated by a scaled-down Active Segmented Mirror of 61 segments which has been developed in-house.

Research paper thumbnail of Book review: Reflecting telescope optics II, by Ray Wilson

The Messenger, Nov 29, 2001

Research paper thumbnail of Active optics in modern large optical telescopes

Research paper thumbnail of Use of Minimum-energy Modes for Modal-active Optics Corrections of Thin Meniscus Mirrors

Journal of Modern Optics, 1991

Abstract For thin meniscus mirrors the modes which correct arbitrary wave-front aberrations in th... more Abstract For thin meniscus mirrors the modes which correct arbitrary wave-front aberrations in the most efficient way are derived. These modes are similar to the free-vibration modes of the mirror. The relationship between the two types of modes is shown. The most important features such as orthogonality and energy of the modes are discussed. This modal approach is applied to a few practical problems in connection with the primary mirrors of the Very Large Telescope of the European Southern Observatory.

Research paper thumbnail of Towards Fully Automated Optimisation of Optical Quality in Telescopes

Research paper thumbnail of Active optics: the NTT and the future

Research paper thumbnail of Performance of spatial filtering wavefront sensor for the phasing of segmented telescopes

The next generation of extremely large telescopes requires the use of segmented mirrors. This tec... more The next generation of extremely large telescopes requires the use of segmented mirrors. This technology needs specific wave front sensors to measure the alignment and phasing state. This paper compares two specific technologies for the measurement of wavefront steps between segments: a simple pin hole and a phase contrast sensor. The efficiency of each sensor will be quantified by calculating the Fisher information, first, under ideal conditions, then including the effects of sampling and atmospheric turbulence.

Research paper thumbnail of Optical analysis of thermally cycled 515 mm metallic Al/Al-alloy mirrors

Astronomy and Astrophysics, 1986

Research paper thumbnail of Phasing segmented deformable mirrors with the Zernike phase contrast method

Astronomical Telescopes and Instrumentation, 2012

Research paper thumbnail of Optical Wavefront Analysis of Thermally Cycled 500 mm Metallic Mirrors

International Astronomical Union Colloquium, 1984

Warping is a major concern in the use of aluminium as a material for large mirrors. The warping c... more Warping is a major concern in the use of aluminium as a material for large mirrors. The warping characteristics are influenced by:*the type of material, i.e. pure aluminium or some alloy*the type of fabrication, i.e. cast, rolled or forged.So far there is little data available on the warping characteristics of aluminium mirrors. Therefore ESO has tested the warping behaviour of 18 aluminium mirrors under thermal cycling conditions with a glass ceramic mirror, which has not been cycled, as a reference mirror. The set of 500 mm mirrors selected for this experiment is described in [1].

Research paper thumbnail of From Passive Support Systems to the NTT Active Support

International Astronomical Union Colloquium, 1984

ESO has two telescope projects: the NTT (New Technology Telescope) with 3.5 m aperture and the VL... more ESO has two telescope projects: the NTT (New Technology Telescope) with 3.5 m aperture and the VLT (Very Large Telescope) with 16 m equivalent aperture. The former is already in the engineering phase and should be completed in 1987; the latter is still in the study phase and will be described at this conference by our colleague, D. Enard.This paper is concerned with the primary support system of the NTT. The basic principles and layout of this support have already been described in the literature 1,2,3).

Research paper thumbnail of Focal-plane wavefront sensing for active optics in the VST based on an analytical optical aberration model

Ground-based and Airborne Telescopes VI, 2016

We study a novel focal plane wavefront sensing and active optics control scheme at the VST on Cer... more We study a novel focal plane wavefront sensing and active optics control scheme at the VST on Cerro Paranal, an f /5.5 survey telescope with a 1Ö1 degree field of view and a 2.6 m primary mirror. This scheme analyzes the elongation pattern of stellar PSFs across the full science image (256 Mpixels) and compares their second moments with an analytical model based on 5th-order geometrical optics. We consider 11 scalar degrees of freedom in mirror misalignments and deformations (M2 piston, tip/tilt and lateral displacement, detector tip/tilt, plus M1 figure astigmatism and trefoil). Using a numerical optimization method, we extract up to 4000 stars and complete the fitting process in under one minute. We demonstrate successful closed-loop active optics control based on maximum likelihood filtering.

Research paper thumbnail of ESO VLT - Primary Mirror Support System

Research paper thumbnail of Towards establishing specifications for large telescopes optics

Very Large Telescopes and Their Instrumentation Vol 1, 1988

Research paper thumbnail of Active optics system of the VLT Survey Telescope

Applied Optics, 2016

This paper describes the active optics system of the VST (VLT Survey Telescope), the 2.6-m survey... more This paper describes the active optics system of the VST (VLT Survey Telescope), the 2.6-m survey telescope designed for visible wavelengths of the European Southern Observatory at Cerro Paranal, in the Atacama desert. The telescope is characterized by a wide field of view (1.42 degree diameter), leading to tighter active optics than in conventional telescopes, in particular for the alignment requirements. We discuss the effects of typical error sources on the image quality and present the specific solutions adopted for wavefront sensing and correction of the aberrations, which are based on the shaping of a monolithic primary mirror and the positioning of the secondary in 5 degrees of freedom.

Research paper thumbnail of Closed-Loop Active Optics: Its Advantages And Limitations For Correction Of Wind-Buffet Deformations Of Large Flexible Mirrors

SPIE Proceedings, 1989

Wind buffet deformation of large flexible mirrors is, from its frequency bandpass and other chara... more Wind buffet deformation of large flexible mirrors is, from its frequency bandpass and other characteristics, an overlap area between normal low bandpass "Active Optics" and high bandpass "Adaptive Optics". The fundamental problem posed is that the time frequencies involved do not permit the elimination of external seeing effects by appropriate time integrations with the image analyser, as in normal low bandpass closed-loop operation. Confusion between the wind deformation and atmospheric functions results. For wind buffet correction in these circumstances, we analyse the possibilities and limitations of the closed-loop principle using one or more image analysers in a number of configurations. Some important parameters of the atmospheric function apear to be insufficiently known and should be measured experimentally if rapid practical progress is to be made. Cross-checks betweens closed-loop and open-loop methods in a two-pronged approach seem highly desirable.

Research paper thumbnail of <title>Exploring model based engineering for large telescopes: getting started with descriptive models</title>

Modeling, Systems Engineering, and Project Management for Astronomy III, 2008

This paper was (will be) published in Proceedings of SPIE Astronomical Telescopes and Instrumenta... more This paper was (will be) published in Proceedings of SPIE Astronomical Telescopes and Instrumentation 2008 and is made available as an electronic reprint (preprint) with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Research paper thumbnail of <title>Measurements of the isoplanatic angle of image motion for angular separations up to 10 arcmin</title>

Advanced Technology Optical Telescopes V, 1994

Star trails have been taken with a CCD-camera covering a field of approximately 10'. With the... more Star trails have been taken with a CCD-camera covering a field of approximately 10'. With the telescope movement stopped the sampling rate was of the order of 40 Hz. The correlations between the centroid variations of different trails, representing the image motion perpendicular to the trails, have been calculated. The power spectra of the centroid motions are used to identify their origin. The method turns out to be feasible for the measurement of the isoplanatic angle of image motion. The results show that the correlations of the image motions can be significantly enhanced, if the time delay due to the movement of the turbulence across the field of the telescope is taken into account.

Research paper thumbnail of Retrofitting New Technology to an Old Telescope

Research paper thumbnail of <title>Disentangling between low order telescope aberrations and segmentation errors using a Shack-Hartmann sensor</title>

Ground-based and Airborne Telescopes II, 2008

ABSTRACT The shape correction of the mirrors is a crucial operation to obtain diffraction limited... more ABSTRACT The shape correction of the mirrors is a crucial operation to obtain diffraction limited images in actively controlled telescopes. If the mirror is not monolithic, the segmentation errors introduced by piston, tip and tilt of the segments are superimposed on the continuous aberrations. In the case of a sensor based on the measurement of the wave front slopes, like the Shack-Hartmann wave front sensor, an algorithm which allows separating the different contributions is necessary for a proper correction. In the framework of the Active Phasing Experiment (APE) carried out at ESO, we have developed a simple algorithm which can be applied to compute the aberrations and the tip-tilt coefficients using the information obtained with a Shack-Hartmann sensor. It is based on the construction of an orthogonal base in the space of the wave front slope functions. The description of the algorithm and its performance in the cases of low-order aberrations superimposed on tip-tilt misalignment of the segments are reported. A particular application of this technique in the case of the European Extremely Large Telescope (E-ELT) is discussed and the expected upper limits for the residual errors after correction are estimated.

Research paper thumbnail of The First Active Segmented Mirror at ESO

The Active Phasing Experiment (APE) is part of the Extremely Large Telescope Design Study which i... more The Active Phasing Experiment (APE) is part of the Extremely Large Telescope Design Study which is supported by the European Framework Programme 6. This experiment, which is conducted in collaboration with several partners is a demonstrator to test and qualify newly-developed phasing sensors for the alignment of segmented mirrors and test the phasing software within a telescope control system to be developed for a future European Extremely Large Telescope. The segmentation of a primary mirror is simulated by a scaled-down Active Segmented Mirror of 61 segments which has been developed in-house.