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Papers by Natalia Yaitskova

Research paper thumbnail of Random Phasor Sum in the Fundamental Work of Lord Rayleigh

Research paper thumbnail of Performance analysis of Mach-Zehnder interferometer for detection of wavefront discontinuities

SPIE Proceedings, 2003

This paper presents a study of the Mach-Zehnder interferometer for the segmentation error measure... more This paper presents a study of the Mach-Zehnder interferometer for the segmentation error measurement in a giant segmented telescope. We present a thorough theoretical anlaysis of the system performance and deliver an analytical formula for the interferometric signal in the Fraunhofer diffraction approximation. We consider the effects which cause system performance degradation, such as gaps and segment edge misfigure. Taking into account photon noise, we determine the limiting star magnitude. A special emphasis is placed on the analysis of system performance in the presence of atmospheric turbulence.

Research paper thumbnail of <title>System design and analysis of the exo-planet imaging camera and spectrograph (EPICS) for the European ELT</title>

Ground-based and Airborne Instrumentation for Astronomy II, 2008

One of the main science objectives of the European ELT is the direct imaging of extrasolar planet... more One of the main science objectives of the European ELT is the direct imaging of extrasolar planets. The large aperture of the telescope has the potential to significantly enlarge the discovery space towards older gas giant exo-planets seen in reflected light. In this paper, we give an overview of the EPICS system design strategy during the phase A study. In

Research paper thumbnail of EPICS: direct imaging of exoplanets with the E-ELT

Research paper thumbnail of <title>The active phasing experiment: Part I. Concept and objectives</title>

Ground-based and Airborne Telescopes, 2006

In a framework of ELT design study our group is building an Active Phasing Experiment (APE), the ... more In a framework of ELT design study our group is building an Active Phasing Experiment (APE), the main goals of which is to demonstrate the non-adaptive wavefront control scheme and technology for Extremely Large Telescope (ELT). The experiment includes verification and test of different phasing sensors and integration of a phasing wavefront sensor into a global scheme of segmented telescope active control. After a sufficient number of tests in the laboratory APE will be mounted and tested on sky at a Nasmyth focus of a VLT unit telescope. The paper presents APE as a demonstrator of particular aspects of ELT and provides a general understanding concerning the strategy of segmented mirrors active control.

Research paper thumbnail of Peculiarity of Lyot Coronagraphy for Highly Segmented Apertures

EAS Publications Series, 2006

The existing high contrast imaging techniques cannot be applied directly to the telescope of the ... more The existing high contrast imaging techniques cannot be applied directly to the telescope of the diameter 30–100 m without taking into account the specific characteristics of a segmented surface. While the increase in telescope diameter is an advantage for the high contrast range science, the segmentation sets a limit on the performance of the coronagraph. In particular, diffraction from intersegment gaps sets a floor to the achievable extinction of the starlight. Masking out the gaps in the Lyot plane although helps increasing the contrast, does not solve completely the problem: the high spatial frequency component of the diffractive light remains. In the paper I suggest using a Lyot stop which produces a phase-amplitude modulation in order to reduce the effect of segmentation.

Research paper thumbnail of Lyot Coronagraphy on Giant Segmented-Mirror Telescopes

Submitted to ApJL We present a study of Lyot style (i.e., classical, band-limited, and Gaussian o... more Submitted to ApJL We present a study of Lyot style (i.e., classical, band-limited, and Gaussian occulter) coronagraphy on extremely large, highly-segmented telescopes. We show that while increased telescope diameter is always an advantage for high dynamic range science (assuming wavefront errors have been corrected sufficiently well), segmentation itself sets a limit on the performance of Lyot coronagraphs. Diffraction from inter-segment gaps sets a floor to the achievable extinction of on-axis starlight with Lyot coronagraphy. We derive an analytical expression for the manner in which coronagraphic suppression of an on-axis source decreases with increasing gap size when the segments are placed in a spatially periodic array over the telescope aperture, regardless of the details of the arrangement. A simple Lyot stop masking out pupil edges produces good extinction of the central peak in the point-spread function (PSF), but leaves satellite images caused by inter-segment gaps essenti...

Research paper thumbnail of Probability density cloud as a geometrical tool to describe statistics of scattered light

Journal of the Optical Society of America A

First-order statistics of scattered light is described using the representation of probability de... more First-order statistics of scattered light is described using the representation of probability density cloud which visualizes a two-dimensional distribution for complex amplitude. The geometric parameters of the cloud are studied in detail and are connected to the statistical properties of phase. The moment-generating function for intensity is obtained in a closed form through these parameters. An example of exponentially modified normal distribution is provided to illustrate the functioning of this geometrical approach.

Research paper thumbnail of <title>Multireference adaptive optics and problem of widening field-of-view</title>

Wave Propagation in the Atmosphere and Adaptive Optics

A new method to overcome the anisoplanatic limitation in adaptive optics is proposed. We show tha... more A new method to overcome the anisoplanatic limitation in adaptive optics is proposed. We show that to enlarge field of view of a conventional adaptive optical system with a single corrector appropriate modification of correction algorithm is required. This modified algorithm is based on wavefront measurements from several guide stars. The number of guide stars and their allocation is studied in terms of field of view size. We develop a method for definition of optimal weight contribution of references into correction function. The method is checked on typical configurations of references. Possible scheme of wavefront reconstruction in multireference adaptive optics is also discussed.

Research paper thumbnail of Telling planets from speckles created by telescope segmentation

Proceedings of Spie the International Society For Optical Engineering, Jul 1, 2010

Research paper thumbnail of Design, analysis and test of a microdots apodizer for the Apodized Pupil Lyot Coronagraph

This paper demonstrates that binary apodizers are well suited for being used in high contrast ima... more This paper demonstrates that binary apodizers are well suited for being used in high contrast imaging coronagraphs. The correct choice of pixel size is important and must be adressed considering the scientific field of view.

Research paper thumbnail of Influence of irregular gaps between primary mirror segments on telescope image quality

Journal of the Optical Society of America a Optics Image Science and Vision, Sep 1, 2007

We study the effect of gaps between the segments on image quality of the extremely large ground-b... more We study the effect of gaps between the segments on image quality of the extremely large ground-based telescope. We show that if the width of the gap changes arbitrarily from one intersegment boundary to another, the regular diffraction pattern is distorted and speckles appear. Two mechanisms producing irregularity in the gaps' distribution are considered: a random shift of the segment's center and an error in the segment's shape. The analytical approach allows an estimation of ensemble averaged characteristics of the point-spread function, such as a halo and high-order diffraction peaks. We deliver simple formulas for the quantitative estimation of the position and the intensity of the halo as well as the intensity of the diffraction peaks.

Research paper thumbnail of Analytical study of detraction effects in extremely large segmented telescopes

Journal of the Optical Society of America a Optics Image Science and Vision, 2003

Research paper thumbnail of Rolled edges and phasing of segmented telescopes presentation

Research paper thumbnail of Field-of-View Widening in Adaptive Optics System

Research paper thumbnail of Influence of atmospheric turbulence on the Zernike phase contrast method and the first steps towards the phasing of segmented deformable mirrors

Adaptive Optics Systems III, 2012

ABSTRACT The Zernike phase contrast sensor has been studied in the framework of the Active Phasin... more ABSTRACT The Zernike phase contrast sensor has been studied in the framework of the Active Phasing Experiment in the laboratory and on sky at the Very Large Telescope. Atmospheric turbulence strongly affects the shape of the signal of the Zernike phase contrast sensor. The first part of these proceedings is dedicated to a study of the influence of atmospheric turbulence on the signal of the Zernike phase contrast sensor. The second part is dedicated to the phasing of segmented deformable mirrors. A new technology of segmented deformable mirrors for adaptive optics made from silicon wafers with bimorph piezoelectric actuation has been proven to work. A demonstrator with three hexagonal segments of 90 mm corner to corner has been built. The morphing capability of the segmented mirror has been studied and validated by simulations and on a test bench. In this paper, we demonstrate with simulations the phasing of the segmented bimorph mirror with the Zernike phase contrast method. Aspects such as phasing in the presence of segment aberrations have been investigated.

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

The shape correction of the mirrors is a crucial operation to obtain diffraction limited images i... more 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 wavefront slopes, like the Shack-Hartmann wavefront 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 an algorithm to compute the continuous aberrations and the tip-tilt coefficients based on the modal wavefront reconstruction. The description of the algorithm and some examples in the cases of low-order aberrations superimposed on tip-tilt misalignment of the segments are reported, with particular emphasis about the effect of the use of a non-orthogonal set of basis functions. The precision achievable with the Shack-Hartmann sensor in APE at VLT and in the case of the European Extremely Large Telescope (E-ELT) is computed and the expected upper limits for the residual errors after correction are finally estimated.

Research paper thumbnail of Statistics of undevelop ed speckles in partially polarized light

1st AO4ELT conference - Adaptive Optics for Extremely Large Telescopes, 2010

We obtain an expression for the probability density function (PDF) of partially developed speckle... more We obtain an expression for the probability density function (PDF) of partially developed speckles formed by light with an arbitrary degree of polarization. From the probability density we calculate the detection threshold corresponding to the 5σ confidence level of a normal distribution. We show that unpolarized light has an advantage in high contrast imaging for low ratios of the deterministic part of the point spread function (DL PSF) to the halo, typical in coronagraphy.

Research paper thumbnail of <title>Modeling in optics with the use of an object-oriented paradigm</title>

Integrated Modeling of Telescopes, 2002

It is shown how an object-oriented approach to modelling in optics can help to create reusable an... more It is shown how an object-oriented approach to modelling in optics can help to create reusable and flexible code. We present a class system which has found its applicaiton as in the task of extended object imaging through the turbulent atmosphere, and the simulation of diffraction properties of the segmented telescope.

Research paper thumbnail of Multireference adaptive optics and field-of-view widening problem

Research paper thumbnail of Random Phasor Sum in the Fundamental Work of Lord Rayleigh

Research paper thumbnail of Performance analysis of Mach-Zehnder interferometer for detection of wavefront discontinuities

SPIE Proceedings, 2003

This paper presents a study of the Mach-Zehnder interferometer for the segmentation error measure... more This paper presents a study of the Mach-Zehnder interferometer for the segmentation error measurement in a giant segmented telescope. We present a thorough theoretical anlaysis of the system performance and deliver an analytical formula for the interferometric signal in the Fraunhofer diffraction approximation. We consider the effects which cause system performance degradation, such as gaps and segment edge misfigure. Taking into account photon noise, we determine the limiting star magnitude. A special emphasis is placed on the analysis of system performance in the presence of atmospheric turbulence.

Research paper thumbnail of <title>System design and analysis of the exo-planet imaging camera and spectrograph (EPICS) for the European ELT</title>

Ground-based and Airborne Instrumentation for Astronomy II, 2008

One of the main science objectives of the European ELT is the direct imaging of extrasolar planet... more One of the main science objectives of the European ELT is the direct imaging of extrasolar planets. The large aperture of the telescope has the potential to significantly enlarge the discovery space towards older gas giant exo-planets seen in reflected light. In this paper, we give an overview of the EPICS system design strategy during the phase A study. In

Research paper thumbnail of EPICS: direct imaging of exoplanets with the E-ELT

Research paper thumbnail of <title>The active phasing experiment: Part I. Concept and objectives</title>

Ground-based and Airborne Telescopes, 2006

In a framework of ELT design study our group is building an Active Phasing Experiment (APE), the ... more In a framework of ELT design study our group is building an Active Phasing Experiment (APE), the main goals of which is to demonstrate the non-adaptive wavefront control scheme and technology for Extremely Large Telescope (ELT). The experiment includes verification and test of different phasing sensors and integration of a phasing wavefront sensor into a global scheme of segmented telescope active control. After a sufficient number of tests in the laboratory APE will be mounted and tested on sky at a Nasmyth focus of a VLT unit telescope. The paper presents APE as a demonstrator of particular aspects of ELT and provides a general understanding concerning the strategy of segmented mirrors active control.

Research paper thumbnail of Peculiarity of Lyot Coronagraphy for Highly Segmented Apertures

EAS Publications Series, 2006

The existing high contrast imaging techniques cannot be applied directly to the telescope of the ... more The existing high contrast imaging techniques cannot be applied directly to the telescope of the diameter 30–100 m without taking into account the specific characteristics of a segmented surface. While the increase in telescope diameter is an advantage for the high contrast range science, the segmentation sets a limit on the performance of the coronagraph. In particular, diffraction from intersegment gaps sets a floor to the achievable extinction of the starlight. Masking out the gaps in the Lyot plane although helps increasing the contrast, does not solve completely the problem: the high spatial frequency component of the diffractive light remains. In the paper I suggest using a Lyot stop which produces a phase-amplitude modulation in order to reduce the effect of segmentation.

Research paper thumbnail of Lyot Coronagraphy on Giant Segmented-Mirror Telescopes

Submitted to ApJL We present a study of Lyot style (i.e., classical, band-limited, and Gaussian o... more Submitted to ApJL We present a study of Lyot style (i.e., classical, band-limited, and Gaussian occulter) coronagraphy on extremely large, highly-segmented telescopes. We show that while increased telescope diameter is always an advantage for high dynamic range science (assuming wavefront errors have been corrected sufficiently well), segmentation itself sets a limit on the performance of Lyot coronagraphs. Diffraction from inter-segment gaps sets a floor to the achievable extinction of on-axis starlight with Lyot coronagraphy. We derive an analytical expression for the manner in which coronagraphic suppression of an on-axis source decreases with increasing gap size when the segments are placed in a spatially periodic array over the telescope aperture, regardless of the details of the arrangement. A simple Lyot stop masking out pupil edges produces good extinction of the central peak in the point-spread function (PSF), but leaves satellite images caused by inter-segment gaps essenti...

Research paper thumbnail of Probability density cloud as a geometrical tool to describe statistics of scattered light

Journal of the Optical Society of America A

First-order statistics of scattered light is described using the representation of probability de... more First-order statistics of scattered light is described using the representation of probability density cloud which visualizes a two-dimensional distribution for complex amplitude. The geometric parameters of the cloud are studied in detail and are connected to the statistical properties of phase. The moment-generating function for intensity is obtained in a closed form through these parameters. An example of exponentially modified normal distribution is provided to illustrate the functioning of this geometrical approach.

Research paper thumbnail of <title>Multireference adaptive optics and problem of widening field-of-view</title>

Wave Propagation in the Atmosphere and Adaptive Optics

A new method to overcome the anisoplanatic limitation in adaptive optics is proposed. We show tha... more A new method to overcome the anisoplanatic limitation in adaptive optics is proposed. We show that to enlarge field of view of a conventional adaptive optical system with a single corrector appropriate modification of correction algorithm is required. This modified algorithm is based on wavefront measurements from several guide stars. The number of guide stars and their allocation is studied in terms of field of view size. We develop a method for definition of optimal weight contribution of references into correction function. The method is checked on typical configurations of references. Possible scheme of wavefront reconstruction in multireference adaptive optics is also discussed.

Research paper thumbnail of Telling planets from speckles created by telescope segmentation

Proceedings of Spie the International Society For Optical Engineering, Jul 1, 2010

Research paper thumbnail of Design, analysis and test of a microdots apodizer for the Apodized Pupil Lyot Coronagraph

This paper demonstrates that binary apodizers are well suited for being used in high contrast ima... more This paper demonstrates that binary apodizers are well suited for being used in high contrast imaging coronagraphs. The correct choice of pixel size is important and must be adressed considering the scientific field of view.

Research paper thumbnail of Influence of irregular gaps between primary mirror segments on telescope image quality

Journal of the Optical Society of America a Optics Image Science and Vision, Sep 1, 2007

We study the effect of gaps between the segments on image quality of the extremely large ground-b... more We study the effect of gaps between the segments on image quality of the extremely large ground-based telescope. We show that if the width of the gap changes arbitrarily from one intersegment boundary to another, the regular diffraction pattern is distorted and speckles appear. Two mechanisms producing irregularity in the gaps' distribution are considered: a random shift of the segment's center and an error in the segment's shape. The analytical approach allows an estimation of ensemble averaged characteristics of the point-spread function, such as a halo and high-order diffraction peaks. We deliver simple formulas for the quantitative estimation of the position and the intensity of the halo as well as the intensity of the diffraction peaks.

Research paper thumbnail of Analytical study of detraction effects in extremely large segmented telescopes

Journal of the Optical Society of America a Optics Image Science and Vision, 2003

Research paper thumbnail of Rolled edges and phasing of segmented telescopes presentation

Research paper thumbnail of Field-of-View Widening in Adaptive Optics System

Research paper thumbnail of Influence of atmospheric turbulence on the Zernike phase contrast method and the first steps towards the phasing of segmented deformable mirrors

Adaptive Optics Systems III, 2012

ABSTRACT The Zernike phase contrast sensor has been studied in the framework of the Active Phasin... more ABSTRACT The Zernike phase contrast sensor has been studied in the framework of the Active Phasing Experiment in the laboratory and on sky at the Very Large Telescope. Atmospheric turbulence strongly affects the shape of the signal of the Zernike phase contrast sensor. The first part of these proceedings is dedicated to a study of the influence of atmospheric turbulence on the signal of the Zernike phase contrast sensor. The second part is dedicated to the phasing of segmented deformable mirrors. A new technology of segmented deformable mirrors for adaptive optics made from silicon wafers with bimorph piezoelectric actuation has been proven to work. A demonstrator with three hexagonal segments of 90 mm corner to corner has been built. The morphing capability of the segmented mirror has been studied and validated by simulations and on a test bench. In this paper, we demonstrate with simulations the phasing of the segmented bimorph mirror with the Zernike phase contrast method. Aspects such as phasing in the presence of segment aberrations have been investigated.

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

The shape correction of the mirrors is a crucial operation to obtain diffraction limited images i... more 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 wavefront slopes, like the Shack-Hartmann wavefront 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 an algorithm to compute the continuous aberrations and the tip-tilt coefficients based on the modal wavefront reconstruction. The description of the algorithm and some examples in the cases of low-order aberrations superimposed on tip-tilt misalignment of the segments are reported, with particular emphasis about the effect of the use of a non-orthogonal set of basis functions. The precision achievable with the Shack-Hartmann sensor in APE at VLT and in the case of the European Extremely Large Telescope (E-ELT) is computed and the expected upper limits for the residual errors after correction are finally estimated.

Research paper thumbnail of Statistics of undevelop ed speckles in partially polarized light

1st AO4ELT conference - Adaptive Optics for Extremely Large Telescopes, 2010

We obtain an expression for the probability density function (PDF) of partially developed speckle... more We obtain an expression for the probability density function (PDF) of partially developed speckles formed by light with an arbitrary degree of polarization. From the probability density we calculate the detection threshold corresponding to the 5σ confidence level of a normal distribution. We show that unpolarized light has an advantage in high contrast imaging for low ratios of the deterministic part of the point spread function (DL PSF) to the halo, typical in coronagraphy.

Research paper thumbnail of <title>Modeling in optics with the use of an object-oriented paradigm</title>

Integrated Modeling of Telescopes, 2002

It is shown how an object-oriented approach to modelling in optics can help to create reusable an... more It is shown how an object-oriented approach to modelling in optics can help to create reusable and flexible code. We present a class system which has found its applicaiton as in the task of extended object imaging through the turbulent atmosphere, and the simulation of diffraction properties of the segmented telescope.

Research paper thumbnail of Multireference adaptive optics and field-of-view widening problem