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van Kooten, M.A.M. (author), Doelman, N.J. (author), Kenworthy, M. (author)For high-contrast imaging systems, such as VLT/SPHERE, the performance of the system at small angular separations is contaminated by the wind-driven halo in the science image. This halo is a result of the servo-lag error in the adaptive optics (AO) system due to the finite time between measuring the wavefront phase and applying the phase...article 2020
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van Kooten, M. (author), Doelman, N.J. (author), Kenworthy, M. (author)For high-contrast imaging systems, the time delay is one of the major limiting factors for the performance of the extreme adaptive optics (AO) sub-system and, in turn, the final contrast. The time delay is due to the finite time needed to measure the incoming disturbance and then apply the correction. By predicting the behavior of the...article 2019
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Saathof, R. (author), den Breeje, R. (author), Klop, W.A. (author), Kuiper, S. (author), Doelman, N.J. (author), Pettazzi, F. (author), Vosteen, L.L.A. (author), Wildschut, J.A. (author), de Lange, T.J. (author), Moens, T.M.N. (author), Koster, S.E. (author), Gruber, J.M. (author), Spierdijk, J.P.F. (author), Kerkhof, P.J. (author), Russchenberg, T. (author), Truyens, D.C. (author), Crowcombe, W.E. (author), Human, J.D. (author), Mata Calvo, R. (author), Poliak, J. (author), Barrios, R. (author), Scalise, S. (author), Ferrario, I. (author)TNO and DLR envision optical free-space communication between ground stations and geostationary telecommunication satellites to replace the traditional RF links for the next generation of Very High Throughput Satellites. To mitigate atmospheric turbulence, an Adaptive Optics (AO) system will be used. TNO and DLR are developing breadboards to...conference paper 2018
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van Kooten, M.A.M. (author), Doelman, N.J. (author), Kenworthy, M. (author)In an adaptive optics (AO) system, finite time delays contribute a relatively large amount to the overall wavefront error. The temporal error, due to the time delays, adds to the speckle halo which is visible in the science plane of a high contrast imaging (HCI) instrument. The halo limits the inner working angle, preventing HCI from probing...conference paper 2018
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Kuiper, S. (author), Doelman, N.J. (author), Overtoom, T. (author), Nieuwkoop, E. (author), Russchenberg, T. (author), van Riel, M.J.C.M. (author), Wildschut, J.A. (author), Baeten, M.J.J. (author), Spruit, W.E.T. (author), Brinkers, S. (author), Human, J.D. (author)To increase the collecting power and to improve the angular imaging resolution, space telescopes are evolving towards larger primary mirrors. The aerial density of the telescope mirrors needs to be kept low, however, to be compatible with the launch requirements. A light-weight (primary) mirror will introduce additional optical aberrations to...conference paper 2017
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van Kooten, M. (author), Doelman, N.J. (author), Kenworthy, M. (author)Current high contrast imaging systems are limited at small angular separations, preventing the direct imaging of Earth-size exoplanets close to their host stars. One primary cause of this is the performance of the extreme adaptive optics (AO) system which is dominated by the servo-lag error at small angular separations. Prediction can be used to...conference paper 2017
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Faber, A.J. (author), Cheng, L.K. (author), Gielesen, W.L.M. (author), Boussard-Plédel, C. (author), Houizot, P. (author), Danto, S. (author), Lucas, J. (author), Pereira Do Carmo, J. (author)The development of single mode chalcogenide glass fibers as wavefront filter for the DARWIN mission is reported. Melting procedures and different preform techniques for manufacturing core-cladding chalcogenide fibers are described. Bulk glass samples on the basis of Te-As-Se- and high Te-compositions have been characterized optically, by...conference paper 2017
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Mora, A. (author), Biermann, M. (author), Bombrun, A. (author), Boyadjian, J. (author), Chassat, F. (author), Corberand, P. (author), Davidson, M. (author), Doyle, D. (author), Escolar, D. (author), Gielesen, W.L.M. (author), Guilpain, T. (author), Hernandez, J. (author), Kirschner, V. (author), Klioner, S.A. (author), Koeck, C. (author), Laine, B. (author), Lindegren, L. (author), Serpell, E. (author), Tatry, P. (author), Thoral, P. (author)The Gaia all-sky astrometric survey is challenged by several issues affecting the spacecraft stability. Amongst them, we find the focus evolution, straylight and basic angle variations Contrary to pre-launch expectations, the image quality is continuously evolving, during commissioning and the nominal mission. Payload decontaminations and...conference paper 2016
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Koek, W.D. (author), van Zwet, E.J. (author)When using a commonly-used quadri-wave lateral shearing interferometer wavefront sensor (QWLSI WFS) for beam size measurements on a high power CO2 laser, artefacts have been observed in the measured irradiance distribution. The grating in the QWLSI WFS not only generates the diffracted first orders that are required for introducing the shear,...conference paper 2015
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Korkiakoski, V. (author), Keller, C.U. (author), Doelman, N.J. (author), Kenworthy, M. (author), Otten, G. (author), Verhaegen, M. (author)We investigate methods to calibrate the non-common path aberrations at an adaptive optics system having a wavefront-correcting device working with an extremely high resolution (larger than 150x150 correcting elements). We use focal-plane images collected successively, the corresponding phase-diversity information and numerically efficient...conference paper 2014
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Mora, A. (author), Biermann, M. (author), Brown, A.G.A. (author), Busonero, D. (author), Carminati, L. (author), Carrasco, J.M. (author), Chassat, F. (author), Erdmann, M. (author), Gielesen, W.L.M. (author), Jordi, C. (author), Katz, D. (author), Kohley, R. (author), Lindegren, L. (author), Loeffler, W. (author), Marchal, O. (author), Panuzzo, P. (author), Seabroke, G. (author), Sahlmann, J. (author), Serpell, E. (author), Serraller, I. (author), van Leeuwen, F. (author), van Reeven, W. (author), van den Dool, T.C. (author), Vosteen, L.L.A. (author)The Gaia payload ensures maximum passive stability using a single material, SiC, for most of its elements. Dedicated metrology instruments are, however, required to carry out two functions: monitoring the basic angle and refocusing the telescope. Two interferometers fed by the same laser are used to measure the basic angle changes at the level...conference paper 2014
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Korkiakoski, V. (author), Doelman, N.J. (author), Codona, J. (author), Kenworthy, M. (author), Otten, G. (author), Keller, C.U. (author)We present a method to calibrate a high-resolution wavefront (WF)-correcting device with a single, static camera, located in the focal-plane; no moving of any component is needed. The method is based on a localized diversity and differential optical transfer functions to compute both the phase and amplitude in the pupil plane located upstream of...article 2013
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Korkiakoski, V. (author), Keller, C.U. (author), Doelman, N.J. (author), Codona, J. (author), Kenworthy, M. (author)We show how differential optical transfer function (dOTF) method is used to calibrate an adaptive optics setup using a spatial light modulator. SLM response, rotation and registration are measured sufficiently accurately for high-order WF correction. © OSA 2013.conference paper 2013
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Mora, A. (author), Vosteen, L.L.A. (author)The ESA Gaia spacecraft has two Shack-Hartmann wavefront sensors (WFS) on its focal plane. They are required to refocus the telescope in-orbit due to launch settings and gravity release. They require bright stars to provide good signal to noise patterns. The centroiding precision achievable poses a limit on the minimum stellar brightness...conference paper 2012
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Andrei, R.M. (author), Fraanje, P.R. (author), Verhaegen, M. (author), Korkiakoski, V.A. (author), Keller, C.U. (author), Doelman, N.J. (author)We propose a new approach for the joint estimation of aberration parameters and unknown object from diversity images with applications in imaging systems with extended objects as astronomical ground-based observations or solar telescopes. The motivation behind our idea is to decrease the computational complexity of the conventional phase...conference paper 2012
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Korkiakoski, V. (author), Keller, C.U. (author), Doelman, N.J. (author), Fraanje, P.R. (author), Verhaegen, M. (author)We study different possibilities to use adaptive optics (AO) and phase diversity (PD) together in a jointly optimized system. The potential of the joint system is demonstrated through numerical simulations. We find that the most significant benefits are obtained from the improved deconvolution of AO-corrected wavefronts and the additional...article 2012
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Andrei, R.M. (author), Smith, C.S. (author), Fraanje, P.R. (author), Verhaegen, M. (author), Korkiakoski, V.A. (author), Keller, C.U. (author), Doelman, N.J. (author)In this paper we give a new wavefront estimation technique that overcomes the main disadvantages of the phase diversity (PD) algorithms, namely the large computational complexity and the fact that the solutions can get stuck in a local minima. Our approach gives a good starting point for an iterative algorithm based on solving a linear system,...conference paper 2012
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Keller, C.U. (author), Korkiakoski, V. (author), Doelman, N.J. (author), Fraanje, P.R. (author), Andrei, R. (author), Verhaegen, M. (author)We present a promising approach to the extremely fast sensing and correction of small wavefront errors in adaptive optics systems. As our algorithm's computational complexity is roughly proportional to the number of actuators, it is particularly suitable to systems with 10,000 to 100,000 actuators. Our approach is based on sequential phase...conference paper 2012
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Meisner, J.A. (author), Jaffe, W.J. (author), le Poole, R.S. (author)The NOVA Fringe Tracker (NFT) is a proposed solution tóthe call by ESO for a second generation fringe tracking facility. This instrument at the VLTI will enable the cophasing of up tó6 telescopes simultaneously. Using broad band optics with detection from 1.2 tó2.4 microns, a unique configuration is employed that eliminates so-called ...conference paper 2012
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Henselmans, R. (author), Nijkerk, M.D. (author), Lemmen, M.H.J. (author), Rijnveld, N. (author), Kamphues, F.G. (author)TNO is developing the Optical Tube Asssemblies (OTAs) for the ESO VLT Four Laser Guide Star Facility. The OTAs are Galilean 20x beam expanders, expanding a Ø15 mm input beam to a steerable Ø300 mm output beam with a wavefront quality requirement of 50 nm rms. The allowed defocus under the influence of the changing environmental air temperature ...conference paper 2011
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