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Latency-Constrained Fading Mitigation for Coherent Optical Feeder Links based on Space-Time-Frequency Coding

Korevaar, C.W. (author), Saathof, R. (author), van Abkoude, Tara (author), Doelman, Niek J. (author)

Optical feeder links (OFLs) benefit from the vast amount of bandwidth available in the THz-regime of the electromagnetic spectrum, and can be considered as enablers for future terabit-per-second satellite systems. A particular challenge for OFLs is to mitigate the effects of fading, caused by a combination of turbulence-induced scintillation,...

conference paper 2023

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Chasing rainbows and ocean glints: Inner working angle constraints for the Habitable Worlds Observatory

Vaughan, Sophia R. (author), Gebhard, Timothy D. (author), Cowan, N.J.P. (author), Doelman, D.S. (author), Kenworthy, M.A. (author), Trees, V.J.H. (author), Stam, D.M. (author), Brandl, B.R. (author), Kleisioti, E. (author)

NASA is engaged in planning for a Habitable Worlds Observatory (HabWorlds), a coronagraphic space mission to detect rocky planets in habitable zones and establish their habitability. Surface liquid water is central to the definition of planetary habitability. Photometric and polarimetric phase curves of starlight reflected by an exoplanet can...

journal article 2023

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Design of the life signature detection polarimeter LSDpol

Keller, Christoph U. (author), Snik, Frans (author), Patty, C. H.Lucas (author), Klindzic, D. (author), Krasteva, Mariya (author), Doelman, David S. (author), Wijnen, T.P.G. (author), Pallichadath, V. (author), Stam, D.M. (author)

Many biologically produced chiral molecules such as amino acids and sugars show a preference for left or right handedness (homochirality). Light reflected by biological materials such as algae and leaves therefore exhibits a small amount of circular polarization that strongly depends on wavelength. Our Life Signature Detection polarimeter ...

conference paper 2020

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Long-term outcomes of the hip shelf arthroplasty in adolescents and adults with residual hip dysplasia: a systematic review

Willemsen, K. (author), Doelman, Christiaan J. (author), Sam, Ali S.Y. (author), Seevinck, Peter R. (author), Sakkers, Ralph J.B. (author), Weinans, Harrie (author), van Der Wal, Bart C.H. (author)

Background and purpose — The shelf arthroplasty was the regular treatment for residual hip dysplasia before it was substituted by the peri-acetabular osteotomy. Yet, evidence regarding the survival of shelf arthroplasty surgery has never been systematically documented. Hence, we investigated the survival time of the shelf procedure until...

journal article 2020

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Rank-based optimization techniques for estimation problems in optics

Doelman, R. (author)

Aberrations in optical systems, such as telescopes and microscopes, degrade the quality of the images that can be produced by these systems. For example, an object that is positioned out of focus produces a blurred image on a camera sensor and the turbulent air in the earth’s atmosphere reduces the imaging performance of telescopes. In this...

doctoral thesis 2019

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Convex optimization-based blind deconvolution for images taken with coherent illumination

Doelman, R. (author), Verhaegen, M.H.G. (author)

A rank-constrained reformulation of the blind deconvolution problem on images taken with coherent illumination is proposed. Since in the reformulation the rank constraint is imposed on a matrix that is affine in the decision variables, we propose a novel convex heuristic for the blind deconvolution problem. The proposed heuristic allows for...

journal article 2019

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Identification of the dynamics of time-varying phase aberrations from time histories of the point-spread function

Doelman, R. (author), Klingspor, Måns (author), Hansson, Anders (author), Löfberg, Johan (author), Verhaegen, M.H.G. (author)

To optimally compensate for time-varying phase aberrations with adaptive optics, a model of the dynamics of the aberrations is required to predict the phase aberration at the next time step. We model the time-varying behavior of a phase aberration, expressed in Zernike modes, by assuming that the temporal dynamics of the Zernike coefficients...

journal article 2019

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Modeling forest plantations for carbon uptake with the LPJmL dynamic global vegetation model

Braakhekke, Maarten C. (author), Doelman, Jonathan C. (author), Baas, P. (author), Müller, Christoph (author), Schaphoff, Sibyll (author), Stehfest, Elke (author), Van Vuuren, Detlef P. (author)

We present an extension of the dynamic global vegetation model, Lund-Potsdam-Jena Managed Land (LPJmL), to simulate planted forests intended for carbon (C) sequestration. We implemented three functional types to simulate plantation trees in temperate, tropical, and boreal climates. The parameters of these functional types were optimized to...

journal article 2019

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Solving large-scale general phase retrieval problems via a sequence of convex relaxations

Doelman, R. (author), Nguyen, Hieu Thao (author), Verhaegen, M.H.G. (author)

We present a convex relaxation-based algorithm for large-scale general phase retrieval problems. General phase retrieval problems include, e.g., the estimation of the phase of the optical field in the pupil plane based on intensity measurements of a point source recorded in the image (focal) plane. The non-convex problem of finding the...

journal article 2018

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Design of an efficient coherent multi-site single-molecule rectifier

Perrin, M.L. (author), Doelman, Matthijs (author), Eelkema, R. (author), van der Zant, H.S.J. (author)

We propose the design of a single-molecule diode with a rectification ratio exceeding a million. The employed mechanism is based on coherent resonant charge transport across a molecule that consists of four conjugated sites coupled by non-conjugated bridges. Using density functional theory calculations, we rationalize the design of the...

journal article 2017

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Sequential convex relaxation for robust static output feedback structured control

Doelman, R. (author), Verhaegen, M.H.G. (author)

We analyse the very general class of uncertain systems that have Linear Fractional Representations (LFRs), and uncertainty blocks in a convex set with a finite number of vertices. For these systems we design static output feedback controllers. In the general case, computing a robust static output feedback controller with optimal performance...

journal article 2017

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Sequential convex relaxation for convex optimization with bilinear matrix equalities

Doelman, R. (author), Verhaegen, M.H.G. (author)

We consider the use of the nuclear norm operator, and its tendency to produce low rank results, to provide a convex relaxation of Bilinear Matrix Inequalities (BMIs). The BMI is first written as a Linear Matrix Inequality (LMI) subject to a bi-affine equality constraint and subsequently rewritten into an LMI subject to a rank constraint on a...

conference paper 2016

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Focal-plane wavefront sensing with high-order adaptive optics systems

Korkiakoski, V.A. (author), Keller, C.U. (author), Doelman, N. (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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Fast & Furious focal-plane wavefront sensing

Korkiakoski, V.A. (author), Keller, C.U. (author), Doelman, N. (author), Kenworthy, M. (author), Otten, G. (author), Verhaegen, M.H.G. (author)

We present two complementary algorithms suitable for using focal-plane measurements to control a wavefront corrector with an extremely high-spatial resolution. The algorithms use linear approximations to iteratively minimize the aberrations seen by the focal-plane camera. The first algorithm, Fast & Furious (FF), uses a weak-aberration...

journal article 2014

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Iterative linear focal-plane wavefront correction

Smith, C.S. (author), Marinica, R.M. (author), Den Dekker, A.J. (author), Verhaegen, M.H.G. (author), Korkiakoski, V. (author), Keller, C.U. (author), Doelman, N. (author)

We propose an efficient approximation to the nonlinear phase diversity (PD) method for wavefront reconstruction and correction from intensity measurements with potential of being used in real-time applications. The new iterative linear phase diversity (ILPD) method assumes that the residual phase aberration is small and makes use of a first...

journal article 2013

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Joint optimization of phase diversity and adaptive optics: Demonstration of potential

Korkiakoski, V. (author), Keller, C.U. (author), Doelman, N. (author), Fraanje, P.R. (author), Verhaegen, M.H.G. (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...

journal article 2011

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Modeling and prediction of turbulence-induced wavefront distortions

Fraanje, R. (author), Doelman, N. (author)

In recent years various researchers have proposed an optimal control approach for the rejection of turbulence-induced wavefront distortions in an AO system. The essential element in the design of an optimal controller is the choice for the turbulence model, which predicts the turbulence to compensate for the inherent delay in the AO control loop...

conference paper 2010

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Fast reconstruction and prediction of frozen flow turbulence based on structured Kalman filtering

Fraanje, P.R. (author), Rice, J. (author), Verhaegen, M. (author), Doelman, N. (author)

Efficient and optimal prediction of frozen flow turbulence using the complete observation history of the wavefront sensor is an important issue in adaptive optics for large ground-based telescopes. At least for the sake of error budgeting and algorithm performance, the evaluation of an accurate estimate of the optimal performance of a particular...

journal article 2010

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Sparse prediction of turbulence in time and space

Fraanje, R. (author), Doelman, N. (author), Verhaegen, M. (author)

Using a matching pursuit (MP) approach to solve least squares problems with a sparsity constraint sparse controllers are computed to compensate for atmospheric turbulence. The method has been validated by simulation of von K´arm´an turbulence with frozen flow for the case of prediction, reconstruction and control.

conference paper 2009

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Validation of a new adaptive deformable mirror concept

Hamelinck, R. (author), Ellenbroek, R. (author), Rosielle, N. (author), Steinbuch, M. (author), Verhaegen, M. (author), Doelman, N. (author)

A new prototype adaptive deformable mirror for future AO-systems is presented that consists of a thin continuous membrane on which push-pull actuators impose out-of-plane displacements. Each actuator has ±10?m stroke, nanometer resolution and only mW’s heat dissipation. The mirror’s modular design makes the mechanics, electronics and control...

conference paper 2008