The Experts below are selected from a list of 3771 Experts worldwide ranked by ideXlab platform
Dimitri Mawet - One of the best experts on this subject based on the ideXlab platform.
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towards high throughput and low order aberration robustness for vortex Coronagraphs with central obstructions
Space Telescopes and Instrumentation 2020: Optical Infrared and Millimeter Wave, 2020Co-Authors: K Fogarty, Dimitri Mawet, Garreth Ruane, Johan Mazoyer, Dan Sirbu, Laurent PueyoAbstract:In order to maximize the potential of the next-generation of large space-based observatory to detect and characterize Earth-like exoplanets, Coronagraphs must be designed that can obtain high (~10-10) contrasts in the presence of realistic low-order aberrations and finite stellar diameters. Unfortunately, for telescopes with central obstructions, maintaining aberration robustness for most coronagraph designs entails significant losses in either throughput or inner working angle. This has resulted in stringent limitations for exo-Earth yields on planned future on-axis telescopes, such as LUVOIR-A. We address this limitation with modified versions of apodized charge 6 and charge 8 vortex Coronagraphs which use multiple stages of focal plane mask. These multi-stage apodized vortex Coronagraphs (MSAVCs) produce dark holes with contrast <10-10 and mitigate the flux due to tip/tilt offsets as large as 0.05 λ/D while obtaining core throughputs that are a factor of ~2 higher than similarly constrained single-stage apodized vortex Coronagraphs. The MSAVCs we present are robust to several low-order aberrations, and we discuss the possibility of explicitly constraining low-order aberrations further. Furthermore, we demonstrate mitigating flux due to misalignment between focal plane masks, thus overcoming a significant hurdle in implementing multi-stage vortex designs. By using a parametric expression to estimate the yield of a charge 6 MSAVC for a 10% central obstruction relative to an off-axis charge 6 vortex coronagraph on an 8-m telescope, we estimate it may be possible to retain ~67% of the off-axis yield
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fast linearized coronagraph optimizer falco iv coronagraph design survey for obstructed and segmented apertures
Space Telescopes and Instrumentation 2018: Optical Infrared and Millimeter Wave, 2018Co-Authors: Garreth Ruane, Dimitri Mawet, Stuart Shaklan, Erkin Sidick, Carl T. Coker, A Riggs, J Jewell, Kunjithapatham Balasubramanian, Christopher C StarkAbstract:Coronagraph instruments on future space telescopes will enable the direct detection and characterization of Earth-like exoplanets around Sun-like stars for the first time. The quest for the optimal optical coronagraph designs has made rapid progress in recent years thanks to the Segmented Coronagraph Design and Analysis (SCDA) initiative led by the Exoplanet Exploration Program at NASA's Jet Propulsion Laboratory. As a result, several types of high-performance designs have emerged that make use of dual deformable mirrors to (1) correct for optical aberrations and (2) suppress diffracted starlight from obstructions and discontinuities in the telescope pupil. However, the algorithms used to compute the optimal deformable mirror surface tend to be computationally intensive, prohibiting large scale design surveys. Here, we utilize the Fast Linearized Coronagraph Optimizer (FALCO), a tool that allows for rapid optimization of deformable mirror shapes, to explore trade-offs in coronagraph designs for obstructed and segmented space telescopes. We compare designs for representative shaped pupil Lyot and vortex Coronagraphs, two of the most promising concepts for the LUVOIR space mission concept. We analyze the optical performance of each design, including their throughput and ability to passively suppress light from partially resolved stars in the presence of low-order aberrations. Our main result is that deformable mirror based apodization can sufficiently suppress diffraction from support struts and inter-segment gaps whose widths are on the order of ~0.1% of the primary mirror diameter to detect Earth-sized planets within a few tens of milliarcseconds from the star.
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performance and sensitivity of vortex Coronagraphs on segmented space telescopes
Techniques and Instrumentation for Detection of Exoplanets VIII, 2017Co-Authors: Garreth Ruane, Dimitri Mawet, Jeffrey Jewell, Stuart ShaklanAbstract:The detection of molecular species in the atmospheres of earth-like exoplanets orbiting nearby stars requires an optical system that suppresses starlight and maximizes the sensitivity to the weak planet signals at small angular separations. Achieving sufficient contrast performance on a segmented aperture space telescope is particularly challenging due to unwanted diffraction within the telescope from amplitude and phase discontinuities in the pupil. Apodized vortex Coronagraphs are a promising solution that theoretically meet the performance needs for high contrast imaging with future segmented space telescopes. We investigate the sensitivity of apodized vortex Coronagraphs to the expected aberrations, including segment co-phasing errors in piston and tip/tilt as well as other low-order and mid-spatial frequency aberrations. Coronagraph designs and their associated telescope requirements are identified for conceptual HabEx and LUVOIR telescope designs.
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the w m keck observatory infrared vortex coronagraph and a first image of hip 79124 b
The Astronomical Journal, 2017Co-Authors: E Serabyn, Olivier Absil, Dimitri Mawet, Michael Bottom, Elsa Huby, Keith Matthews, Bruno Femenia, Peter Wizinowich, Mikael Karlsson, Randy CampbellAbstract:An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L'-band observational mode is described, and an initial demonstration of the new capability is presented: a resolved image of the low-mass companion to HIP 79124, which had previously been detected by means of interferometry. With HIP 79124 B at a projected separation of 186.5 mas, both the small inner working angle of the vortex coronagraph and the related imaging improvements were crucial in imaging this close companion directly. Due to higher Strehl ratios and more relaxed contrasts in L' band versus H band, this new coronagraphic capability will enable high-contrast, small-angle observations of nearby young exoplanets and disks on a par with those of shorter-wavelength extreme adaptive optics Coronagraphs.
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the w m keck observatory infrared vortex coronagraph and a first image of hip79124 b
arXiv: Solar and Stellar Astrophysics, 2016Co-Authors: E Serabyn, Olivier Absil, Dimitri Mawet, Michael Bottom, Elsa Huby, Keith Matthews, Bruno Femenia, Peter Wizinowich, Mikael Karlsson, Randy CampbellAbstract:An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L'-band observational mode is described, and an initial demonstration of the new capability is presented: a resolved image of the low-mass companion to HIP79124, which had previously been detected by means of interferometry. With HIP79124 B at a projected separation of 186.5 mas, both the small inner working angle of the vortex coronagraph and the related imaging improvements were crucial in imaging this close companion directly. Due to higher Strehl ratios and more relaxed contrasts in L' band versus H band, this new coronagraphic capability will enable high-contrast small-angle observations of nearby young exoplanets and disks on a par with those of shorter-wavelength extreme adaptive optics Coronagraphs.
Olivier Guyon - One of the best experts on this subject based on the ideXlab platform.
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laboratory and on sky validation of the shaped pupil coronagraph s sensitivity to low order aberrations with active wavefront control
Publications of the Astronomical Society of the Pacific, 2018Co-Authors: Olivier Guyon, Nemanja Jovanovic, Jeremy N Kasdin, Tyler Groff, Thayne Currie, Julien Lozi, Timothy D Brandt, Frantz MartinacheAbstract:We present early laboratory simulations and extensive on-sky tests validating of the performance of a shaped pupil coronagraph (SPC) behind an extreme-AO corrected beam of the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system. In tests with the SCExAO internal source/wavefront error simulator, the normalized intensity profile for the SPC degrades more slowly than for the Lyot coronagraph as low-order aberrations reduce the Strehl ratio from extremely high values (S.R. ~ 0.93–0.99) to those characteristic of current ground-based extreme AO systems (S.R. ~ 0.74–0.93) and then slightly lower values down to S.R. ~ 0.57. On-sky SCExAO data taken with the SPC and other Coronagraphs for brown dwarf/planet-hosting stars HD 1160 and HR 8799 provide further evidence for the SPC's robustness to low-order aberrations. From H-band Strehl ratios of 80% to 70%, the Lyot coronagraph's performance versus that of the SPC may degrade even faster on sky than is seen in our internal source simulations. The 5-σ contrast also degrades faster (by a factor of two) for the Lyot than the SPC. The SPC we use was designed as a technology demonstrator only, with a contrast floor, throughput, and outer working angle poorly matched for SCExAO's current AO performance and poorly tuned for imaging the HR 8799 planets. Nevertheless, we detect HR 8799 cde with SCExAO/CHARIS using the SPC in broadband mode, where the S/N for planet e is within 30% of that obtained using the vortex coronagraph. The shaped-pupil coronagraph is a promising design demonstrated to be robust in the presence of low-order aberrations and may be well-suited for future ground and space-based direct imaging observations, especially those focused on follow-up exoplanet characterization and technology demonstration of deep contrast within well-defined regions of the image plane.
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ground based adaptive optics coronagraphic performance under closed loop predictive control
arXiv: Instrumentation and Methods for Astrophysics, 2017Co-Authors: Jared R Males, Olivier GuyonAbstract:The discovery of the exoplanet Proxima b highlights the potential for the coming generation of giant segmented mirror telescopes (GSMTs) to characterize terrestrial --- potentially habitable --- planets orbiting nearby stars with direct imaging. This will require continued development and implementation of optimized adaptive optics systems feeding Coronagraphs on the GSMTs. Such development should proceed with an understanding of the fundamental limits imposed by atmospheric turbulence. Here we seek to address this question with a semi-analytic framework for calculating the post-coronagraph contrast in a closed-loop AO system. We do this starting with the temporal power spectra of the Fourier basis calculated assuming frozen flow turbulence, and then apply closed-loop transfer functions. We include the benefits of a simple predictive controller, which we show could provide over a factor of 1400 gain in raw PSF contrast at 1 $\lambda/D$ on bright stars, and more than a factor of 30 gain on an I = 7.5 mag star such as Proxima. More sophisticated predictive control can be expected to improve this even further. Assuming a photon noise limited observing technique such as High Dispersion Coronagraphy, these gains in raw contrast will decrease integration times by the same large factors. Predictive control of atmospheric turbulence should therefore be seen as one of the key technologies which will enable ground-based telescopes to characterize terrrestrial planets.
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design fabrication and testing of stellar Coronagraphs for exoplanet imaging
Techniques and Instrumentation for Detection of Exoplanets VIII 2017, 2017Co-Authors: Justin Knight, Olivier Guyon, John Brewer, Ryan Hamilton, Tom D Milster, Karen WardAbstract:Complex-mask Coronagraphs destructively interfere unwanted starlight with itself to enable direct imaging of exoplanets. This is accomplished using a focal plane mask (FPM); a FPM can be a simple occulter mask, or in the case of a complex-mask, is a multi-zoned device designed to phase-shift starlight over multiple wavelengths to create a deep achromatic null in the stellar point spread function. Creating these masks requires microfabrication techniques, yet many such methods remain largely unexplored in this context. We explore methods of fabrication of complex FPMs for a Phased-Induced Amplitude Apodization Complex-Mask Coronagraph (PIAACMC). Previous FPM fabrication efforts for PIAACMC have concentrated on mask manufacturability while modeling science yield, as well as assessing broadband wavelength operation. Moreover current fabrication efforts are concentrated on assessing coronagraph performance given a single approach. We present FPMs fabricated using several process paths, including deep reactive ion etching and focused ion beam etching using a silicon substrate. The characteristic size of the mask features is 5μm with depths ranging over 1μm. The masks are characterized for manufacturing quality using an optical interferometer and a scanning electron microscope. Initial testing is performed at the Subaru Extreme Adaptive Optics testbed, providing a baseline for future experiments to determine and improve coronagraph performance within fabrication tolerances.
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lyot based low order wavefront sensor for phase mask Coronagraphs principle simulations and laboratory experiments
Publications of the Astronomical Society of the Pacific, 2014Co-Authors: Garima Singh, Frantz Martinache, Pierre Baudoz, Olivier Guyon, Taro Matsuo, Nemanja Jovanovic, Christophe ClergeonAbstract:High performance coronagraphic imaging of faint structures around bright stars at small angular separations requires fine control of tip, tilt, and other low order aberrations. When such errors occur upstream of a coronagraph they result in starlight leakage, which reduces the dynamic range of the instrument. This issue has been previously addressed for occulting Coronagraphs by sensing the starlight before or at the coronagraphic focal plane. One such solution, the coronagraphic low order wave-front sensor (CLOWFS), uses a partially reflective focal plane mask to measure pointing errors for Lyot-type Coronagraphs. To deal with pointing errors in low inner working angle phase mask Coronagraphs which do not have a reflective focal plane mask, we have adapted the CLOWFS technique. This new concept relies on starlight diffracted by the focal plane phase mask being reflected by the Lyot stop towards a sensor which reliably measures low order aberrations such as tip and tilt. This reflective Lyot-based wavefront sensor is a linear reconstructor which provides high sensitivity tip-tilt error measurements with phase mask Coronagraphs. Simulations show that the measurement accuracy of pointing errors with realistic post adaptive optics residuals are ≈10-2λ/D per mode at λ = 1.6 μm for a four quadrant phase mask. In addition, we demonstrate the open loop measurement pointing accuracy of 10-2λ/D at 638 nm for a four quadrant phase mask in the laboratory.
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central obscuration removal plates for focal plane phase mask Coronagraphs with a centrally obscured telescope
Publications of the Astronomical Society of the Pacific, 2014Co-Authors: Fumika Oshiyama, Frantz Martinache, Olivier Guyon, Taro Matsuo, Naoshi Murakami, Naoshi Baba, Jun Nishikawa, Motohide TamuraAbstract:Focal-plane phase-mask Coronagraphs, such as eight-octant phase-mask Coronagraphs (8OPM), are one of the most promising tools for high contrast observations. However, coronagraphic performance would be degraded when combined with a centrally-obscured telescope. We propose pupil-remapping optics for removing the shade of a secondary mirror to generate a clear, circular pupil for the phase-mask coronagraph. First, we show the design of the pupil-remapping optics, called central-obscuration removal plates (CRPs). Next, we report laboratory experiments on the 8OPM coronagraph using manufactured CRPs. We also evaluate off-axis point-spread functions via both laboratory experiments and numerical simulations. Finally, we evaluate, via numerical simulations, limiting factors for coronagraphic performance, such as phase aberrations introduced by the CRPs, the effect of Fresnel diffraction, and chromatic behavior. The numerical simulations suggest that the phase aberrations could be a dominant limiting factor of the achievable contrast in the current laboratory experiments.
Pierre Baudoz - One of the best experts on this subject based on the ideXlab platform.
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review of high contrast imaging systems for current and future ground and space based telescopes i coronagraph design methods and optical performance metrics
arXiv: Instrumentation and Methods for Astrophysics, 2018Co-Authors: Garreth Ruane, Pierre Baudoz, Raphael Galicher, Johan Mazoyer, Mamadou Ndiaye, A J Riggs, Emiel H Por, Elsa Huby, Ewan S DouglasAbstract:The Optimal Optical Coronagraph (OOC) Workshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this first installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of design methods and optical performance metrics developed for coronagraph instruments. The design and optimization of Coronagraphs for future telescopes has progressed rapidly over the past several years in the context of space mission studies for Exo-C, WFIRST, HabEx, and LUVOIR as well as ground-based telescopes. Design tools have been developed at several institutions to optimize a variety of coronagraph mask types. We aim to give a broad overview of the approaches used, examples of their utility, and provide the optimization tools to the community. Though it is clear that the basic function of Coronagraphs is to suppress starlight while maintaining light from off-axis sources, our community lacks a general set of standard performance metrics that apply to both detecting and characterizing exoplanets. The attendees of the OOC workshop agreed that it would benefit our community to clearly define quantities for comparing the performance of coronagraph designs and systems. Therefore, we also present a set of metrics that may be applied to theoretical designs, testbeds, and deployed instruments. We show how these quantities may be used to easily relate the basic properties of the optical instrument to the detection significance of the given point source in the presence of realistic noise.
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laboratory validation of the dual zone phase mask coronagraph in broadband light at the high contrast imaging thd testbed
Astronomy and Astrophysics, 2016Co-Authors: J R Delorme, Remi Soummer, Pierre Baudoz, Raphael Galicher, Kjetil Dohlen, A. Caillat, Mamadou Ndiaye, Gerard Rousset, Olivier DupuisAbstract:Context. Specific high-contrast imaging instruments are mandatory to characterize circumstellar disks and exoplanets around nearby stars. Coronagraphs are commonly used in these facilities to reject the diffracted light of an observed star and enable direct imaging and spectroscopy of its circumstellar environment. One important property of the coronagraph is to be able to work in broadband light. Aims. Among several proposed Coronagraphs, the dual-zone phase mask coronagraph is a promising solution for starlight rejection in broadband light. In this paper, we perform the first validation of this concept in laboratory. Methods. First, we consider the principle of the dual-zone phase mask coronagraph. Then, we describe the high-contrast imaging THD testbed, the manufacturing of the components, and the quality control procedures. Finally, we study the sensitivity of our coronagraph to low-order aberrations (inner working angle and defocus) and estimate its contrast performance. Our experimental broadband light results are compared with numerical simulations to check agreement with the performance predictions. Results. With the manufactured prototype and using a dark hole technique based on the self-coherent camera, we obtain contrast levels down to 2 × 10 -8 between 5 and 17 λ 0 / D in monochromatic light (640 nm). We also reach contrast levels of 4 × 10 -8 between 7 and 17 λ 0 / D in broadband ( λ 0 = 675 nm, Δ λ = 250 and Δ λ / λ 0 = 40%), which demonstrates the excellent chromatic performance of the dual-zone phase mask coronagraph. Conclusions. The performance reached by the dual-zone phase mask coronagraph is promising for future high-contrast imaging instruments that aim to detect and spectrally characterize old or light gaseous planets.
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Laboratory validation of the dual-zone phase mask coronagraph in broadband light at the high-contrast imaging THD testbed
Astronomy and Astrophysics - A&A, 2016Co-Authors: J R Delorme, Remi Soummer, Pierre Baudoz, Raphael Galicher, Kjetil Dohlen, A. Caillat, Gerard Rousset, M. N'diaye, Olivier DupuisAbstract:Context. Specific high-contrast imaging instruments are mandatory to characterize circumstellar disks and exoplanets around nearby stars. Coronagraphs are commonly used in these facilities to reject the di ff racted light of an observed star and enable direct imaging and spectroscopy of its circumstellar environment. One important property of the coronagraph is to be able to work in broadband light. Aims. Among several proposed Coronagraphs, the dual-zone phase mask coronagraph is a promising solution for starlight rejection in broadband light. In this paper, we perform the first validation of this concept in laboratory. Methods. First, we consider the principle of the dual-zone phase mask coronagraph. Then, we describe the high-contrast imaging THD testbed, the manufacturing of the components, and the quality control procedures. Finally, we study the sensitivity of our coronagraph to low-order aberrations (inner working angle and defocus) and estimate its contrast performance. Our experimental broadband light results are compared with numerical simulations to check agreement with the performance predictions. Results. With the manufactured prototype and using a dark hole technique based on the self-coherent camera, we obtain contrast levels down to 2 x 10 8 between 5 and 17 lambda(0)/D in monochromatic light (640 nm). We also reach contrast levels of 4 x 10(-8) between 7 and 17 lambda(0)/D in broadband (lambda(0) = 675 nm, Delta lambda = 250 and Delta lambda/lambda(0) = 40%), which demonstrates the excellent chromatic performance of the dual-zone phase mask coronagraph. Conclusions. The performance reached by the dual-zone phase mask coronagraph is promising for future high-contrast imaging instruments that aim to detect and spectrally characterize old or light gaseous planets.
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lyot based low order wavefront sensor for phase mask Coronagraphs principle simulations and laboratory experiments
Publications of the Astronomical Society of the Pacific, 2014Co-Authors: Garima Singh, Frantz Martinache, Pierre Baudoz, Olivier Guyon, Taro Matsuo, Nemanja Jovanovic, Christophe ClergeonAbstract:High performance coronagraphic imaging of faint structures around bright stars at small angular separations requires fine control of tip, tilt, and other low order aberrations. When such errors occur upstream of a coronagraph they result in starlight leakage, which reduces the dynamic range of the instrument. This issue has been previously addressed for occulting Coronagraphs by sensing the starlight before or at the coronagraphic focal plane. One such solution, the coronagraphic low order wave-front sensor (CLOWFS), uses a partially reflective focal plane mask to measure pointing errors for Lyot-type Coronagraphs. To deal with pointing errors in low inner working angle phase mask Coronagraphs which do not have a reflective focal plane mask, we have adapted the CLOWFS technique. This new concept relies on starlight diffracted by the focal plane phase mask being reflected by the Lyot stop towards a sensor which reliably measures low order aberrations such as tip and tilt. This reflective Lyot-based wavefront sensor is a linear reconstructor which provides high sensitivity tip-tilt error measurements with phase mask Coronagraphs. Simulations show that the measurement accuracy of pointing errors with realistic post adaptive optics residuals are ≈10-2λ/D per mode at λ = 1.6 μm for a four quadrant phase mask. In addition, we demonstrate the open loop measurement pointing accuracy of 10-2λ/D at 638 nm for a four quadrant phase mask in the laboratory.
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multi stage four quadrant phase mask achromatic coronagraph for space based and ground based telescopes
Astronomy and Astrophysics, 2011Co-Authors: Raphael Galicher, Pierre Baudoz, Jacques BaudrandAbstract:Context. Less than 3% of the known exoplanets were directly imaged for two main reasons. They are angularly very close to their parent star, which is several magnitudes brighter. Direct imaging of exoplanets thus requires a dedicated instrumentation with large telescopes and accurate wavefront control devices for high-angular resolution and Coronagraphs for attenuating the stellar light. Coronagraphs are usually chromatic and they cannot perform high-contrast imaging over a wide spectral bandwidth. That chromaticity will be critical for future instruments. Aims. Enlarging the coronagraph spectral range is a challenge for future exoplanet imaging instruments on both space- and groundbased telescopes. Methods. We propose the multi-stage four-quadrant phase mask that associates several monochromatic four-quadrant phase mask Coronagraphs in series. Monochromatic device performance has already been demonstrated and the manufacturing procedures are well-under control since their development for previous instruments on VLT and JWST. The multi-stage implementation simplicity is thus appealing. Results. We present the instrument principle and we describe the laboratory performance for large spectral bandwidths and for both pupil shapes for space- (off-axis telescope) and ground-based (E-ELT) telescopes. Conclusions. The multi-stage four-quadrant phase mask reduces the stellar flux over a wide spectral range and it is a very good candidate to be associated with a spectrometer for future exoplanet imaging instruments in ground- and space-based observatories.
Laurent Pueyo - One of the best experts on this subject based on the ideXlab platform.
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towards high throughput and low order aberration robustness for vortex Coronagraphs with central obstructions
Space Telescopes and Instrumentation 2020: Optical Infrared and Millimeter Wave, 2020Co-Authors: K Fogarty, Dimitri Mawet, Garreth Ruane, Johan Mazoyer, Dan Sirbu, Laurent PueyoAbstract:In order to maximize the potential of the next-generation of large space-based observatory to detect and characterize Earth-like exoplanets, Coronagraphs must be designed that can obtain high (~10-10) contrasts in the presence of realistic low-order aberrations and finite stellar diameters. Unfortunately, for telescopes with central obstructions, maintaining aberration robustness for most coronagraph designs entails significant losses in either throughput or inner working angle. This has resulted in stringent limitations for exo-Earth yields on planned future on-axis telescopes, such as LUVOIR-A. We address this limitation with modified versions of apodized charge 6 and charge 8 vortex Coronagraphs which use multiple stages of focal plane mask. These multi-stage apodized vortex Coronagraphs (MSAVCs) produce dark holes with contrast <10-10 and mitigate the flux due to tip/tilt offsets as large as 0.05 λ/D while obtaining core throughputs that are a factor of ~2 higher than similarly constrained single-stage apodized vortex Coronagraphs. The MSAVCs we present are robust to several low-order aberrations, and we discuss the possibility of explicitly constraining low-order aberrations further. Furthermore, we demonstrate mitigating flux due to misalignment between focal plane masks, thus overcoming a significant hurdle in implementing multi-stage vortex designs. By using a parametric expression to estimate the yield of a charge 6 MSAVC for a 10% central obstruction relative to an off-axis charge 6 vortex coronagraph on an 8-m telescope, we estimate it may be possible to retain ~67% of the off-axis yield
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Capabilities of ACAD-OSM, an active method for the correction of aperture discontinuities
2020Co-Authors: Johan Mazoyer, Laurent Pueyo, Kevin Fogarty, Lucie Leboulleux, Mamadou N'diaye, Sylvain Egron, Colin NormanAbstract:The increasing complexity of the aperture geometry of the future space- and ground based-telescopes will limit the performance of the next generation of coronagraphic instruments for high contrast imaging of exoplanets. We propose here a new closed-loop optimization technique using two deformable mirrors to correct for the effects of complex apertures on coronagraph performance, alternative to the ACAD technique previously developed by our group. This technique, ACAD-OSM, allows the use of any Coronagraphs designed for continuous apertures, with complex, segmented, apertures, maintaining high performance in contrast and throughput. We show the capabilities of this technique on several pupil geometries (segmented LUVOIR type aperture, WFIRST, ELTs) for which we obtained high contrast levels with several deformable mirror setups (size, number of actuators, separation between them), Coronagraphs (apodized pupil Lyot and vortex Coronagraphs) and spectral bandwidths, which will help us present recommendations for future coronagraphic instruments. We show that this active technique handles, without any revision to the algorithm, changing or unknown optical aberrations or discontinuities in the pupil, including optical design misalignments, missing segments and phase errors.
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apodized pupil lyot Coronagraphs with arbitrary aperture telescopes novel designs using hybrid focal plane masks
Space Telescopes and Instrumentation 2018: Optical Infrared and Millimeter Wave, 2018Co-Authors: Mamadou Ndiaye, Alexis Carlotti, Remi Soummer, Kjetil Dohlen, Johan Mazoyer, Laurent Pueyo, Kevin Fogarty, Kathryn St Laurent, Neil T ZimmermanAbstract:Exoplanet imaging and spectroscopy are now routinely achieved by dedicated instruments on large ground-based observatories (e.g. Gemini/GPI, VLT/SPHERE, or Subaru/SCExAO). In addition to extreme adaptive optics (ExAO) and post-processing methods, these facilities make use of the most advanced Coronagraphs to suppress light of an observed star and enable the observation of circumstellar environments. The Apodized Pupil Lyot Coronagraph (APLC) is one of the leading coronagraphic baseline in the current generation of instruments. This concept combines a pupil apodization, an opaque focal plane mask (FPM), and a Lyot stop. APLC can be optimized for a range of applications and designs exist for on-axis segmented aperture telescopes at 1010 contrast in broadband light. In this communication, we propose novel designs to push the limits of this concept further by modifying the nature of the FPM from its standard opaque mask to a smaller size occulting spot surrounded by circular phase shifting zones. We present the formalism of this new concept which solutions find two possible applications: 1) upgrades for the current generation of ExAO Coronagraphs since these solutions remain compatible with the existing designs and will provide better inner working angle, contrast and throughput, and 2) coronagraphy at 1010 contrast for future flagship missions such as LUVOIR, with the goal to increase the throughput of the existing designs for the observation of Earth-like planets around nearby stars.
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polynomial apodizers for centrally obscured vortex Coronagraphs
The Astronomical Journal, 2017Co-Authors: Kevin Fogarty, Johan Mazoyer, Laurent Pueyo, Mamadou NdiayeAbstract:Several coronagraph designs have been proposed over the last two decades to directly image exoplanets. Among these designs, the vector vortex Coronagraphs provide theoretically perfect starlight cancellation along with small inner working angles when deployed on telescopes with unobstructed pupils. However, current and planned space missions and ground-based extremely large telescopes present complex pupil geometries, including secondary mirror central obscurations, that prevent vortex Coronagraphs from rejecting on-axis sources entirely. Recent solutions combining the vortex phase mask with a ring-apodized pupil have been proposed to circumvent this issue, but provide a limited throughput for vortex charges $>2$. We present a family of pupil plane apodizations that compensate for pupil geometries with circularly symmetric central obstructions caused by on-axis secondary mirrors for charge 2, 4, and 6 vector vortex Coronagraphs. These apodizations are derived analytically and allow the vortex coronagraph to retain theoretically perfect nulling in the presence of central obscurations. For a charge 4 vortex, we design polynomial apodization functions assuming a greyscale apodizing filter that represent a substantial gain in throughput over the ring-apodized vortex coronagraph design, while for a charge 6 vortex, we design polynomial apodized vortex Coronagraphs that have $\gtrsim 70\%$ total energy throughput for the entire range of central obscuration sizes studied. We propose methods for optimizing apodizations produced with either greyscale apodizing filters or shaped mirrors. We conclude by demonstrating how this design may be combined with apodizations numerically optimized for struts and segment gaps in telescope pupils to design terrestrial exoplanet imagers for complex pupils.
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tip tilt optimizations for polynomial apodized vortex Coronagraphs on obscured telescope pupils
Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, 2017Co-Authors: Johan Mazoyer, Laurent Pueyo, Kevin Fogarty, Mamadou NdiayeAbstract:Obstructions due to large secondary mirrors, primary mirror segmentation, and secondary mirror support struts all introduce diffraction artifacts that limit the performance offered by Coronagraphs. However, just as vortex Coronagraphs provides theoretically ideal cancellation of on-axis starlight for clear apertures, the Polynomial Apodized Vortex Coronagraph (PAVC) completely blocks on-axis light for apertures with central obscurations, and delivers off-axis throughput that improves as the topological charge of the vortex increases. We examine the sensitivity of PAVC designs to tip/tilt aberrations and stellar angular size, and discuss methods for mitigating these effects. By imposing additional constraints on the pupil plane apodization, we decrease the sensitivity of the PAVC to the small positional shifts of the on-axis source induced by either tip/tilt or stellar angular size; providing a route to overcoming an important hurdle facing the performance of vortex Coronagraphs on telescopes with complicated pupils.
Remi Soummer - One of the best experts on this subject based on the ideXlab platform.
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apodized pupil lyot Coronagraphs with arbitrary aperture telescopes novel designs using hybrid focal plane masks
Space Telescopes and Instrumentation 2018: Optical Infrared and Millimeter Wave, 2018Co-Authors: Mamadou Ndiaye, Alexis Carlotti, Remi Soummer, Kjetil Dohlen, Johan Mazoyer, Laurent Pueyo, Kevin Fogarty, Kathryn St Laurent, Neil T ZimmermanAbstract:Exoplanet imaging and spectroscopy are now routinely achieved by dedicated instruments on large ground-based observatories (e.g. Gemini/GPI, VLT/SPHERE, or Subaru/SCExAO). In addition to extreme adaptive optics (ExAO) and post-processing methods, these facilities make use of the most advanced Coronagraphs to suppress light of an observed star and enable the observation of circumstellar environments. The Apodized Pupil Lyot Coronagraph (APLC) is one of the leading coronagraphic baseline in the current generation of instruments. This concept combines a pupil apodization, an opaque focal plane mask (FPM), and a Lyot stop. APLC can be optimized for a range of applications and designs exist for on-axis segmented aperture telescopes at 1010 contrast in broadband light. In this communication, we propose novel designs to push the limits of this concept further by modifying the nature of the FPM from its standard opaque mask to a smaller size occulting spot surrounded by circular phase shifting zones. We present the formalism of this new concept which solutions find two possible applications: 1) upgrades for the current generation of ExAO Coronagraphs since these solutions remain compatible with the existing designs and will provide better inner working angle, contrast and throughput, and 2) coronagraphy at 1010 contrast for future flagship missions such as LUVOIR, with the goal to increase the throughput of the existing designs for the observation of Earth-like planets around nearby stars.
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laboratory validation of the dual zone phase mask coronagraph in broadband light at the high contrast imaging thd testbed
Astronomy and Astrophysics, 2016Co-Authors: J R Delorme, Remi Soummer, Pierre Baudoz, Raphael Galicher, Kjetil Dohlen, A. Caillat, Mamadou Ndiaye, Gerard Rousset, Olivier DupuisAbstract:Context. Specific high-contrast imaging instruments are mandatory to characterize circumstellar disks and exoplanets around nearby stars. Coronagraphs are commonly used in these facilities to reject the diffracted light of an observed star and enable direct imaging and spectroscopy of its circumstellar environment. One important property of the coronagraph is to be able to work in broadband light. Aims. Among several proposed Coronagraphs, the dual-zone phase mask coronagraph is a promising solution for starlight rejection in broadband light. In this paper, we perform the first validation of this concept in laboratory. Methods. First, we consider the principle of the dual-zone phase mask coronagraph. Then, we describe the high-contrast imaging THD testbed, the manufacturing of the components, and the quality control procedures. Finally, we study the sensitivity of our coronagraph to low-order aberrations (inner working angle and defocus) and estimate its contrast performance. Our experimental broadband light results are compared with numerical simulations to check agreement with the performance predictions. Results. With the manufactured prototype and using a dark hole technique based on the self-coherent camera, we obtain contrast levels down to 2 × 10 -8 between 5 and 17 λ 0 / D in monochromatic light (640 nm). We also reach contrast levels of 4 × 10 -8 between 7 and 17 λ 0 / D in broadband ( λ 0 = 675 nm, Δ λ = 250 and Δ λ / λ 0 = 40%), which demonstrates the excellent chromatic performance of the dual-zone phase mask coronagraph. Conclusions. The performance reached by the dual-zone phase mask coronagraph is promising for future high-contrast imaging instruments that aim to detect and spectrally characterize old or light gaseous planets.
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Laboratory validation of the dual-zone phase mask coronagraph in broadband light at the high-contrast imaging THD testbed
Astronomy and Astrophysics - A&A, 2016Co-Authors: J R Delorme, Remi Soummer, Pierre Baudoz, Raphael Galicher, Kjetil Dohlen, A. Caillat, Gerard Rousset, M. N'diaye, Olivier DupuisAbstract:Context. Specific high-contrast imaging instruments are mandatory to characterize circumstellar disks and exoplanets around nearby stars. Coronagraphs are commonly used in these facilities to reject the di ff racted light of an observed star and enable direct imaging and spectroscopy of its circumstellar environment. One important property of the coronagraph is to be able to work in broadband light. Aims. Among several proposed Coronagraphs, the dual-zone phase mask coronagraph is a promising solution for starlight rejection in broadband light. In this paper, we perform the first validation of this concept in laboratory. Methods. First, we consider the principle of the dual-zone phase mask coronagraph. Then, we describe the high-contrast imaging THD testbed, the manufacturing of the components, and the quality control procedures. Finally, we study the sensitivity of our coronagraph to low-order aberrations (inner working angle and defocus) and estimate its contrast performance. Our experimental broadband light results are compared with numerical simulations to check agreement with the performance predictions. Results. With the manufactured prototype and using a dark hole technique based on the self-coherent camera, we obtain contrast levels down to 2 x 10 8 between 5 and 17 lambda(0)/D in monochromatic light (640 nm). We also reach contrast levels of 4 x 10(-8) between 7 and 17 lambda(0)/D in broadband (lambda(0) = 675 nm, Delta lambda = 250 and Delta lambda/lambda(0) = 40%), which demonstrates the excellent chromatic performance of the dual-zone phase mask coronagraph. Conclusions. The performance reached by the dual-zone phase mask coronagraph is promising for future high-contrast imaging instruments that aim to detect and spectrally characterize old or light gaseous planets.
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apodized pupil lyot Coronagraphs for arbitrary apertures iii quasi achromatic solutions
The Astrophysical Journal, 2011Co-Authors: Remi Soummer, Laurent Pueyo, Anand Sivaramakrishnan, Bruce Macintosh, Ben R OppenheimerAbstract:Direct imaging and spectroscopy of young giant planets from the ground requires broadband starlight suppression with coronagraphy. It is important to minimize the coronagraph chromatic sensitivity to help remove residual speckles through post-processing of images at multiple wavelengths. The coronagraph must also be able to mitigate the effects of ground-based telescopes with central obstruction. We present new properties of the Apodized Pupil Lyot Coronagraph (APLC) that enable quasi-achromatic starlight suppression over a broad bandpass (20%) and with central obstructions. We discuss the existence of these quasi-achromatic solutions using the properties of the generalized prolate spheroidal functions, which are used to define the apodizer profile. We discuss a broadband optimization method and illustrate its parameter space in terms of inner working angle and contrast. These new APLC solutions are implemented in the Gemini Planet Imager (GPI), a new facility instrument to detect and characterize young giant planets and disks, which will be commissioned in 2011. The coronagraph design delivers a contrast better than 10–7 beyond a separation of 0.2 arcsec in the presence of Gemini's central obstruction over a 20% bandpass. The science camera is an integral field spectrograph observing in one of the Y, J, or H, or in about two-thirds of the K bandpass, at a single time. Similar solutions have also been used for the Palomar 1640 coronagraphic integral field spectrograph.
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high performance piaa coronagraphy with complex amplitude focal plane masks
Astrophysical Journal Supplement Series, 2010Co-Authors: Ruslan Belikov, Frantz Martinache, Olivier Guyon, Remi SoummerAbstract:We describe a coronagraph approach where the performance of a Phase-Induced Amplitude Apodization (PIAA) coronagraph is improved by using a partially transmissive phase-shifting focal plane mask and a Lyot stop. This approach combines the low inner working angle offered by phase mask coronagraphy, the full throughput and uncompromized angular resolution of the PIAA approach, and the design flexibility of Apodized Pupil Lyot Coronagraph. A PIAA complex mask coronagraph (PIAACMC) is fully described by the focal plane mask size, or, equivalently, its complex transmission which ranges from 0 (opaque) to -1 (phase shifting). For all values of the transmission, the PIAACMC theoretically offers full on-axis extinction and 100% throughput at large angular separations. With a pure phase focal plane mask (complex transmission = -1), the PIAACMC offers 50% throughput at 0.64 {lambda}/D while providing total extinction of an on-axis point source. This performance is very close to the 'fundamental performance limit' of coronagraphy derived from first principles. For very high contrast level, imaging performance with PIAACMC is in practice limited by the angular size of the on-axis target (usually a star). We show that this fundamental limitation must be taken into account when choosing the optimal value of the focal planemore » mask size in the PIAACMC design. We show that the PIAACMC enables visible imaging of Jupiter-like planets at {approx}1.2 {lambda}/D from the host star, and can therefore offer almost three times more targets than a PIAA coronagraph optimized for this type of observation. We find that for visible imaging of Earth-like planets, the PIAACMC gain over a PIAA is probably much smaller, as coronagraphic performance is then strongly constrained by stellar angular size. For observations at 'low' contrast (below {approx} 10{sup 8}), the PIAACMC offers significant performance enhancement over PIAA. This is especially relevant for ground-based high contrast imaging systems in the near-IR, where PIAACMC enables high contrast high efficiency imaging within 1 {lambda}/D. Manufacturing tolerances for the focal plane mask are quantified for a few representative PIAACMC designs.« less
