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Radhakrishnan, V.M. (author), Keller, C.U. (author), Doelman, N.J. (author), Por, E.H. (author)The focal-plane contrast of exoplanet imagers is affected by non-common path aberrations (NCPAs) that the adaptive optics system cannot correct for because they occur after the wavefront has been measured. NCPA estimation is commonly based on the long-exposure science image. Phase retrieval algorithms are often used, and they mostly assume that...article 2023
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Klop, W.A. (author), Saathof, R. (author), Doelman, N.J. (author), Gruber, M. (author), Moens, T.M.N. (author), Osorio Tamayo, C.I. (author), Duque, C.M. (author)Free space optical (FSO) satellite communications has very attractive properties for Quantum Key Distribution(QKD). The quantum channel loss and noise are major factors in setting the maximum achievable secure key rate of QKD systems. Primarily for a LEO satellite node and the BB84 protocol a number of technologies are proposed to reduce the...conference paper 2021
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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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Silvestri, F. (author), Pettazzi, F. (author), Eschen, M. (author), Boschma, J.J. (author), Lutgerink, J.B. (author), Kramer, G.F.IJ. (author), Korevaar, W.C. (author), den Breeje, R. (author), Duque, C.M. (author), Doelman, N.J. (author)Optical satellite communication is growing fast and among various applications it requires higher throughput optical feeder links. Optical feeder links for satellite communication necessitate very high data throughput, up to 1 Terabit/s and beyond. Amongst several multiplexing strategies, dense wavelength division holds a key position to enable...conference paper 2020
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Doelman, N.J. (author)An analytical expression is given for the minimum of the time-delay induced wavefront error (also known as the servo-lag error) in Adaptive Optics systems under temporal prediction filtering. The analysis is based on the von Kármán model for the spectral density of refractive index fluctuations and the hypothesis of frozen flow. An optimal,...article 2020
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van Kooten, M.A.M. (author), Kenworthy, M. (author), Doelman, N.J. (author)Dedicated transiting surveys, such as the Kepler space telescope, have provided the astronomy community with a rich data set resulting in many new discoveries. In this paper, we look at eight Kepler objects identified by Wheeler & Kipping with a periodic, broad increase in flux, that look distinctly different from intrinsic star variability. We...article 2020
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van den Brand, H. (author), Bongers, W.A. (author), Stober, J.K. (author), Kasparek, W. (author), Wagner, D. (author), Doelman, N.J. (author), Klop, W.A. (author), Giannone, L. (author), Reich, M. (author), Westerhof, E. (author), de Baar, M.R. (author)The successful use of a tokamak for generating fusion power requires an active control of magnetic instabilities, such as neoclassical tearing modes (NTMs). Commonly, the NTM location is determined using electron cyclotron emission (ECE) and this is used to apply electron cyclotron heating (ECH) on the NTM location. In this paper, an inline ECE...article 2019
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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), Doelman, N.J. (author), Moens, T.M.N. (author), Gruber, J.M. (author), Russchenberg, T. (author), Pettazzi, F. (author), Human, J.D. (author), Mata Calvo, R. (author), Poliak, J. (author), Barrios, R. (author), Richerzhagen, M. (author), Ferrario, I. (author)For the next generation of very high throughput communication satellites, free-space optical (FSO) communication between ground stations and geostationary telecommunication satellites is likely to replace conventional RF links. To mitigate atmospheric turbulence, TNO and DLR propose Adaptive Optics (AO) to apply uplink pre-correction. In order...conference paper 2019
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Dresscher, M. (author), Human, J.D. (author), Witvoet, G. (author), van der Heiden, N. (author), den Breeje, R. (author), Kuiper, S. (author), Fritz, E.C. (author), Korevaar, C.W. (author), van der Valk, N.C.J. (author), de Lange, T.J. (author), Saathof, R. (author), Doelman, N.J. (author), Crowcombe, W.E. (author), Duque, C.M. (author), de Man, H. (author)The anticipated capacity benefit of optical satellite communications has triggered a cascade of technology developments. In this paper, we present three such technologies, namely; i). A cube satellite laser terminal (CubeCAT), ii). A lower Earth orbit satellite optical head (LEOCAT) and iii). A calibration and verification test bench for coarse...conference paper 2019
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Kuiper, S. (author), Doelman, N.J. (author), Human, J.D. (author), Saathof, R. (author), Klop, W.A. (author), Maniscalco, M.P. (author)TNO is developing Deformable Mirror (DM) technology, targeted for aberration correction in high-end Adaptive Optics (AO) applications in the field of lithography, astronomy, space and laser communication. The heart of this deformable mirror technology is a unique actuator technology based on the variable reluctance principle. The main advantages...conference paper 2018
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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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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), Truyens, D.C. (author), Crowcombe, W.E. (author), Human, J.D. (author), Ferrario, I. (author), Calvo, R.M. (author), Poliak, J. (author), Barrios, R. (author), Giggenbach, D. (author), Fuchs, C. (author), Scalise, S. (author)To overcome data rate limitations of RF communication links with satellites, TNO and DLR envision optical free-space communication feeder links for next generation high throughput satellites. This paper provides a feasibility assessment of such links and the technology needed. The main results of the link budget and the turbulence modeling of...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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Radhakrishnan, V.M. (author), Keller, C.U. (author), Doelman, N.J. (author)Direct imaging of exoplanets requires overcoming the enormous contrast between the exoplanet and its host star, to distinguish the reflected light from the exoplanet, from the diffracted light of the star. Direct optimization of contrast, using nonlinear optimization techniques of the Adaptive Optics (AO) system coupled with coronagraphy, shows...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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- Alberti, S. (author), Genoud, J. (author), Goodman, T. (author), Hogge, J.P. (author), Porte, L. (author), Silva, M. (author), Tran, T.M. (author), Tran, M.Q. (author), Avramidis, K. (author), Pagonakis, I. (author), Jin, J. (author), Illy, S. (author), Gantenbein, G. (author), Jelonnek, J. (author), Thumm, M. (author), Bin, W. (author), Bruschi, A. (author), Garavaglia, S. (author), Moro, A. (author), Kasparek, W. (author), Legrand, F. (author), Perial, E. (author), Rozier, Y. (author), Cismondi, F. (author), Doelman, N.J. (author) conference paper 2017
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Kasparek, W. (author), Doelman, N.J. (author), Stober, J. (author), Maraschek, M. (author), Zohm, H. (author), Monaco, F. (author), Eixenberger, H. (author), Klop, W.A. (author), Wagner, D. (author), Schubert, M. (author), Schütz, H. (author), Grünwald, G. (author), Plaum, B. (author), Munk, R. (author), Schlüter, K.H. (author)At the tokamak ASDEX Upgrade, experiments to stabilize neoclassical tearing modes (NTMs) by electron cyclotron (EC) heating and current drive in the O-points of the magnetic islands were performed. For the rst time, injection into the O-points of the revolving islands was performed via a fast directional switch, which toggled the EC power...article 2016
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Doelman, N.J. (author), Osborn, J. (author)There is a strong need to model the temporal fluctuations in turbulence parameters, for instance for scheduling, simulation and prediction purposes. This paper aims at modelling the dynamic behaviour of the turbulence coherence length r0, utilising measurement data from the Stereo-SCIDAR instrument installed at the Isaac Newton Telescope at La...conference paper 2016