Dr. Neil T. Zimmerman Profile

Dr. Neil T. Zimmerman

Research Astrophysicist at NASA Goddard Space Flight Ctr

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Profile Summary

Neil Zimmerman is a Research Astrophysicist in the Exoplanets and Stellar Astrophysics Laboratory at NASA's Goddard Space Flight Center. He is a member of the WFIRST Project Science team, and his research encompasses coronagraph design and simulation, data processing and extraction, and spectroscopy technologies for future exoplanet imaging missions.

Publications (66)

Proceedings Article | 6 October 2023 Presentation

RST CGI: final verification and calibration of prism and polarizer flight units

Tyler Groff, Neil Zimmerman, Hari Subedi, John Titus, Dylan Bell, Guangjun Gao, Samuel Gaylin, Nicholas Nicolaeff, Toru Yamada, Motohide Tamura

Proceedings Volume 12680, 126800W (2023) https://doi.org/10.1117/12.2677576

KEYWORDS: Prisms, Calibration, Polarizers, Polarization, Spectroscopes, Spectral resolution, Equipment, Target detection, Space telescopes, Signal to noise ratio

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Proceedings Article | 5 October 2023 Presentation + Paper

High-contrast Jacobian-free wavefront control: simulations, experimental results, and extensions to adaptive control

Scott Will, Tyler Groff, Rémi Soummer, Hari Subedi, Laurent Pueyo, Marshall Perrin, Emiel Por, Neil Zimmerman, Michael McElwain, Christopher Stark, Roser Juanola-Parramon

Proceedings Volume 12680, 126801E (2023) https://doi.org/10.1117/12.2677396

KEYWORDS: Coronagraphy, Actuators, Simulations, Wavefronts, Mathematical optimization, Algorithm development, Matrices, Observatories, Wavefront sensors, Wavefront reconstruction, Exoplanets, Computational imaging

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Proceedings Article | 5 October 2023 Presentation + Paper

Nancy Grace Roman Space Telescope coronagraph instrument overview and status

Vanessa Bailey, Eduardo Bendek, Brian Monacelli, Caleb Baker, Gasia Bedrosian, Eric Cady, Ewan Douglas, Tyler Groff, Sergi Hildebrandt, N. Jeremy Kasdin, John Krist, Bruce Macintosh, Bertrand Mennesson, Patrick Morrissey, Ilya Poberezhskiy, Hari Subedi, Jason Rhodes, Aki Roberge, Marie Ygouf, Robert Zellem, Feng Zhao, Neil Zimmerman

Proceedings Volume 12680, 126800T (2023) https://doi.org/10.1117/12.2679036

KEYWORDS: Coronagraphy, Equipment, Mirrors, Optical benches, Wavefront sensors, Deformable mirrors, Cameras, Prisms, Observatories, Wavefront errors

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Proceedings Article | 5 October 2023 Poster + Paper

Coronagraph design survey for future exoplanet direct imaging space missions: interim update

Ruslan Belikov, Christopher Stark, Nick Siegler, Emiel Por, Bertrand Mennesson, Pin Chen, Kevin Fogarty, Olivier Guyon, Roser Juanola-Parramon, John Krist, Dimitri Mawet, Camilo Mejia Prada, Jeremy Kasdin, Laurent Pueyo, Susan Redmond, Garreth Ruane, Dan Sirbu, Karl Stapelfeldt, John Trauger, Neil Zimmerman

Proceedings Volume 12680, 126802G (2023) https://doi.org/10.1117/12.2677732

KEYWORDS: Coronagraphy, Design and modelling, Telescopes, Equipment, Exoplanets, Observatories, Wavefronts, Yield improvement, Planets

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Proceedings Article | 29 August 2022 Presentation

ExoEarth yield estimates for the LUVOIR-A coronagraph instrument

Roser Juanola-Parramon, Christopher Stark, Neil Zimmerman, Axel Potier, Garreth Ruane

Proceedings Volume 12180, 1218021 (2022) https://doi.org/10.1117/12.2629617

KEYWORDS: Coronagraphy, Wavefronts, Wavefront sensors, Exoplanets, Ultraviolet radiation, UV optics, Telescopes, Stars, Spectrographs, Space operations

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Proceedings Article | 27 August 2022 Presentation + Paper

Nancy Grace Roman Space Telescope coronagraph instrument observation calibration plan

Robert Zellem, Bijan Nemati, Guillermo Gonzalez, Marie Ygouf, Vanessa Bailey, Eric Cady, M. Mark Colavita, Sergi Hildebrandt, Erin Maier, Bertrand Mennesson, Lindsey Payne, Neil Zimmerman, Ruslan Belikov, Robert De Rosa, John Debes, Ewan Douglas, Julien Girard, Tyler Groff, Jeremy Kasdin, Patrick Lowrance, Bruce Macintosh, Daniel Ryan, Carey Weisberg

Proceedings Volume 12180, 121801Z (2022) https://doi.org/10.1117/12.2627567

KEYWORDS: Calibration, Stars, Coronagraphy, Planets, Sensors, Polarization, Point spread functions, Error analysis, Signal to noise ratio, Uranus

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Proceedings Article | 27 August 2022 Presentation + Paper

The Roman Space Telescope coronagraph technology demonstration: current status and relevance to future missions

B. Mennesson, V. Bailey, R. Zellem, S. Hildebrandt, M. Ygouf, J. Rhodes, N. Zimmerman, B. Nemati, G. Gonzalez, E. Cady, B. Kern, T. Koch, J. Krist, K. Heydorff, T. Luchik, F. Mok, P. Morrissey, I. Poberezhskiy, A. Riggs, F. Shi, F. Zhao, R. Akeson, L. Armus, A. Greenbaum, J. Ingalls, P. Lowrance

Proceedings Volume 12180, 121801W (2022) https://doi.org/10.1117/12.2629176

KEYWORDS: Coronagraphy, Wavefront sensors, Electron multiplying charge coupled devices, Imaging spectroscopy, Wavefronts, Stars, Spectroscopy, Performance modeling, Cameras, Observatories

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Proceedings Article | 27 August 2022 Poster + Paper

Simulated design trades for a visible-wavelength integral field spectrograph operating behind a space coronagraph

Tyler Baines, Neil Zimmerman, Roser Juanola-Parramon, Nicholas Susemiehl, Avi Mandell, Tyler Groff, Michael McElwain, Christopher Stark, Geronimo Villaneuva, Maxime Rizzo

Proceedings Volume 12180, 121805F (2022) https://doi.org/10.1117/12.2630443

KEYWORDS: Iterated function systems, Planets, Spectral resolution, Coronagraphy, Exoplanets, Sensors, Signal to noise ratio, Device simulation, Spectrographs, Oxygen

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Proceedings Article | 27 August 2022 Poster + Paper

APLC-optimization: an apodized pupil Lyot coronagraph design survey toolkit

Bryony Nickson, Emiel Por, Meiji Nguyen, Rémi Soummer, Iva Laginja, Ananya Sahoo, Laurent Pueyo, Katheryn St. Laurent, Mamadou N’Diaye, Neil Zimmerman, James Noss, Marshall Perrin

Proceedings Volume 12180, 121805K (2022) https://doi.org/10.1117/12.2630686

KEYWORDS: Apodization, Exoplanets, Optical design software, Optimization (mathematics), Design and modelling, Coronagraphy, Telescopes, Tolerancing, Image segmentation, Optical instrument design, Gemini Planet Imager, Point spread functions, Error analysis, Space telescopes, Software development

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SPIE Journal Paper | 19 July 2022 Open Access

Modeling and performance analysis of the LUVOIR coronagraph instrument

Roser Juanola-Parramon, Neil Zimmerman, Laurent Pueyo, Matthew Bolcar, Qian Gong, Tyler Groff, John Krist, Aki Roberge, Garreth Ruane, Christopher Stark

JATIS, Vol. 8, Issue 03, 034001, (July 2022) https://doi.org/10.1117/12.10.1117/1.JATIS.8.3.034001

KEYWORDS: Coronagraphy, Wavefronts, Mirrors, Telescopes, Performance modeling, Stars, Instrument modeling, Planets, Exoplanets, Point spread functions

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Proceedings Article | 1 September 2021 Poster + Paper

Flight mask designs of the Roman Space Telescope coronagraph instrument

A. J. Eldorado Riggs, Vanessa Bailey, Dwight Moody, Erkin Sidick, Kunjithapatham Balasubramanian, Douglas Moore, Daniel Wilson, Garreth Ruane, Dan Sirbu, Jessica Gersh-Range, John Trauger, Bertrand Mennesson, Nicholas Siegler, Eduardo Bendek, Tyler Groff, Neil Zimmerman, John Debes, Scott Basinger, N. Jeremy Kasdin

Proceedings Volume 11823, 118231Y (2021) https://doi.org/10.1117/12.2598599

KEYWORDS: Coronagraphy, Photomasks, Exoplanets, Polarimetry, Spectroscopy, Space telescopes

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Proceedings Article | 1 September 2021 Presentation + Paper

The Roman Space Telescope coronagraph technology demonstration: current status and relevance to future missions

B. Mennesson, V. P. Bailey, R. Zellem, N. Zimmerman, M. Ygouf, S. Hildebrandt, J. Rhodes, J. Kasdin, B. Macintosh, M. Turnbull, E. Douglas, A. Mandell, B. Nemati, G. Gonzalez, E. Cady, B. Kern, J. Krist, F. Shi, F. Mok, P. Morrissey, K. Heydorff, I. Pobereszhskiy, F. Zhao, T. Luchik, E. Maier, R. Akeson, L. Armus, J. Ingalls, P. Lowrance, T. Meshkat

Proceedings Volume 11823, 1182310 (2021) https://doi.org/10.1117/12.2603343

KEYWORDS: Coronagraphy, Electron multiplying charge coupled devices, Wavefront sensors, Cameras, Wavefronts, Imaging spectroscopy, Stars, Imaging systems, Spectroscopy, Polarimetry

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SPIE Journal Paper | 28 May 2021 Open Access

Community exoplanet imaging data challenge for Roman CGI and starshade rendezvous

Margaret Turnbull, Neil Zimmerman, Julien Girard, Sergi R. Hildebrandt, Zhexing Li, Ell Bogat, Junellie Gonzalez-Quiles, Christopher Stark, Avi Mandell, Tiffany Meshkat, Stephen Kane

JATIS, Vol. 7, Issue 02, 021218, (May 2021) https://doi.org/10.1117/12.10.1117/1.JATIS.7.2.021218

KEYWORDS: Planets, Exoplanets, Imaging systems, Signal to noise ratio, Stars, Coronagraphy, Telescopes, Data modeling, Point spread functions, Sensors

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Operating in an unprecedented contrast regime (10 − 7 to 10 − 9), the Roman Coronagraph Instrument (CGI) will serve as a pathfinder for key technologies needed for future Earth-finding missions such as HabEx and LUVOIR. The Roman Exoplanet Imaging Data Challenge (Roman EIDC) was a community engagement effort that tasked participants with extracting exoplanets and their orbits for a 47-UMa-like target star given: (1) 15 years of simulated precursor radial velocity (RV) data and (2) six epochs of simulated imaging taken over the course of the Roman mission. Led by the Turnbull CGI Science Investigation Team, the Roman EIDC was preceded by four tutorial “hack-a-thon” events in Baltimore, Pasadena, New York City, and Tokyo. The Roman EIDC officially launched in October 2019 and ran for 8 months, offering a unique opportunity for exoplanet scientists of all experience levels to get acquainted with realistic near-future imaging data. The Roman EIDC simulated images include four epochs with CGI’s Hybrid Lyot Coronagraph (HLC) plus two epochs with a starshade (SS) assumed to arrive as part of a Starshade Rendezvous later in the mission. We focus on our in-house analysis of the outermost planet “d,” for which the SS’s higher throughput and lower noise floor present a factor of ∼4 improvement in the signal-to-noise ratio over the narrow-field HLC. We find that, although the RV detection was marginal for planet d, the precursor RV data enabled the mass and orbit to be constrained with only two epochs of SS imaging. Including the HLC images in the analysis results in improved measurements over RV + SS alone, with the greatest gains resulting from images taken at epochs near maximum elongation. Combining the two epochs of SS imaging with the RV + HLC data resulted in a factor of ∼2 better orbit and mass determinations over RV + HLC alone. In summary, the Roman CGI, combined with precursor RV data and latermission SS imaging, forms a powerful trifecta in detecting exoplanets and determining their masses, albedos, and system configurations. While the Roman CGI will break new scientific and technological ground with direct imaging of giant exoplanets within ∼5 AU of V ˜ 5 and brighter stars, a Roman Starshade Rendezvous mission would additionally enable the detection of planets out to ∼8 AU in those systems.

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Proceedings Article | 7 January 2021 Poster + Paper

Roman Space Telescope CGI: prism and polarizer characterization modes

Tyler Groff, Neil Zimmerman, Hari Subedi, Maxime Rizzo, John Titus, Jim Lyons, Dylan Bell, Samuel Gaylin, Guangjun Gao, Bert Pasquale, Nicholas Nicolaeff, Motohide Tamura, Fang Shi

Proceedings Volume 11443, 114433D (2021) https://doi.org/10.1117/12.2562925

KEYWORDS: Prisms, Polarizers, Polarization, Spectral calibration, Spectroscopes, Planets, Spectral resolution, Optical design, Calibration, Coronagraphy

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Proceedings Article | 15 December 2020 Poster + Paper

ExoSpec project: an exoplanet spectroscopy technology research collaboration based at NASA’s Goddard Space Flight Center and Ames Research Center

Neil Zimmerman, Michael McElwain, Tyler Groff, Roser Juanola-Parramon, Avi Mandell, Mark Marley, Bernard Rauscher, Hari Subedi, Tyler Baines, Natasha Batalha, Aki Roberge, Adam J. R. W. Smith, Christopher Stark, Nicholas Susemiehl

Proceedings Volume 11443, 114433T (2020) https://doi.org/10.1117/12.2562872

KEYWORDS: Exoplanets, Atmospheric modeling, Spectroscopes, Spectroscopy, Instrument modeling, Atmospheric sensing, Space operations, Wavefronts, Control systems, Sensor performance

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Proceedings Article | 15 December 2020 Poster + Presentation + Paper

The Roman exoplanet imaging data challenge: a major community engagement effort

Julien Girard, Ell Bogat, Junellie Gonzalez-Quiles, Sergi Hildebrandt, Stephen Kane, Zhexing Li, Margaret Turnbull, Christopher Stark, Avi Mandell, Tiffany Meshkat, Neil Zimmerman

Proceedings Volume 11443, 1144337 (2020) https://doi.org/10.1117/12.2561736

KEYWORDS: Exoplanets, Coronagraphy, Planets, Imaging systems, Stars, Point spread functions, Astrophysics, Contamination, Light, Wavefronts

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Proceedings Article | 15 December 2020 Presentation + Paper

The Nancy Grace Roman Space Telescope Coronagraph Instrument (CGI) technology demonstration

N. Jeremy Kasdin, Vanessa Bailey, Bertrand Mennesson, Robert Zellem, Marie Ygouf, Jason Rhodes, Thomas Luchik, Feng Zhao, A. J. Eldorado Riggs, Byoung-Joon Seo, John Krist, Brian Kern, Hong Tang, Bijan Nemati, Tyler Groff, Neil Zimmerman, Bruce Macintosh, Margaret Turnbull, John Debes, Ewan Douglas, Roxana Lupu

Proceedings Volume 11443, 114431U (2020) https://doi.org/10.1117/12.2562997

KEYWORDS: Coronagraphy, Imaging spectroscopy, Planets, Infrared telescopes, James Webb Space Telescope, Imaging systems, Wavefronts, Algorithm development, Jupiter, Infrared radiation

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Proceedings Article | 9 September 2019 Presentation + Paper

The LUVOIR Extreme Coronagraph for Living Planetary Systems (ECLIPS) II. Performance evaluation, aberration sensitivity analysis and exoplanet detection simulations

Roser Juanola-Parramon, Neil Zimmerman, Laurent Pueyo, Matthew Bolcar, Garreth Ruane, John Krist, Tyler Groff

Proceedings Volume 11117, 1111702 (2019) https://doi.org/10.1117/12.2530356

KEYWORDS: Coronagraphy, Exoplanetary science, Telescopes, Wavefronts, Planets, Stars, Planetary systems, Wavefront sensors, Space operations, Exoplanets

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Proceedings Article | 9 September 2019 Presentation

High-contrast imager for complex aperture telescopes (HiCAT): 6. Two deformable mirror wavefront control (Conference Presentation)

Rémi Soummer, Iva Laginja, Scott Will, Roser Juanola-Parramon, Peter Petrone, Greg Brady, James Noss, Marshall Perrin, Julia Fowler, Heather Kurtz, Kathryn St. Laurent, Kevin Fogarty, Evelyn McChesney, Nathan Scott, Keira Brooks, Thomas Comeau, Marc Ferrari, Rob Gontrum, John Hagopian, Emmanuel Hugot, Lucie Leboulleux, Johan Mazoyer, Laurent Mugnier, Mamadou N'Diaye, Laurent Pueyo, Jean-François Sauvage, Ron Shiri, Anand Sivaramakrishnan, Ana-Maria Valenzuela, Neil Zimmerman

Proceedings Volume 11117, 111171Y (2019) https://doi.org/10.1117/12.2530299

KEYWORDS: Telescopes, Deformable mirrors, Imaging systems, Wavefronts, Wavefront sensors, Coronagraphy, Cameras, Ultraviolet telescopes, Image segmentation, Space telescopes

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Proceedings Article | 9 September 2019 Presentation + Paper

Overview of the optomechanical design of the LUVOIR instruments

James Corsetti, Matthew Bolcar, Julie Crooke, Brian Fleming, Kevin France, Joseph Generie, Qian Gong, Tyler Groff, Jason Hylan, Andrew Jones, Lia Sacks, Garrett West, Kan Yang, Neil Zimmerman

Proceedings Volume 11115, 111150X (2019) https://doi.org/10.1117/12.2530695

KEYWORDS: Optomechanical design, Imaging systems, Stars, Galactic astronomy, Telescopes, Optical design, Space telescopes, Astronomy, Astrophysics, Exoplanets

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Proceedings Article | 9 September 2019 Presentation + Paper

The LUVOIR Extreme Coronagraph for Living Planetary Systems (ECLIPS) I: searching and characterizing exoplanetary gems

L. Pueyo, C. Stark, R. Juanola-Parramon, N. Zimmerman, M. Bolcar, A. Roberge, G. Arney, G. Ruane, A. Riggs, R. Belikov, D. Sirbu, D. Redding, R. Soummer, I. Laginja, S. Will

Proceedings Volume 11117, 1111703 (2019) https://doi.org/10.1117/12.2530722

KEYWORDS: Coronagraphy, Exoplanets, Astrophysics, Planets, Stars, Imaging systems, Planetary systems, Cameras, Wavefront sensors, Observatories

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Proceedings Article | 9 September 2019 Paper

Development of the WFIRST CGI integral field spectrograph

Tyler Groff, Neil Zimmerman, Maxime Rizzo, Samuel Gaylin, Nicholas Nicolaeff, John Titus, Rose Mountcastle, Qian Gong, David Harvey

Proceedings Volume 11117, 111170D (2019) https://doi.org/10.1117/12.2530731

KEYWORDS: Iterated function systems, Spectrographs, Imaging spectroscopy, Planets, Coronagraphy, Observatories, Spectral resolution, Exoplanets, Spectroscopes, Visible radiation

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SPIE Journal Paper | 20 May 2019

ExoEarth yield landscape for future direct imaging space telescopes

Christopher Stark, Rus Belikov, Matthew Bolcar, Eric Cady, Brendan Crill, Steve Ertel, Tyler Groff, Sergi Hildebrandt, John Krist, P. Douglas Lisman, Johan Mazoyer, Bertrand Mennesson, Bijan Nemati, Laurent Pueyo, Bernard Rauscher, A. J. Riggs, Garreth Ruane, Stuart Shaklan, Dan Sirbu, Rémi Soummer, Kathryn St. Laurent, Neil Zimmerman

JATIS, Vol. 5, Issue 02, 024009, (May 2019) https://doi.org/10.1117/12.10.1117/1.JATIS.5.2.024009

KEYWORDS: Coronagraphy, Stars, Telescopes, Planets, Space telescopes, Optical instrument design, Point spread functions, Mirrors, Exoplanets, Sensors

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SPIE Journal Paper | 9 May 2019 Open Access

Optical design of the Extreme Coronagraph for Living Planetary Systems instrument for the LUVOIR mission study

Qian Gong, Matthew Bolcar, James Corsetti, Julie Crooke, Joseph Generie, Tyler Groff, Jason Hylan, Andrew Jones, Roser Juanola Parramon, Avi Mandell, Garrett J. West, Neil Zimmerman

JATIS, Vol. 5, Issue 02, 025002, (May 2019) https://doi.org/10.1117/12.10.1117/1.JATIS.5.2.025002

KEYWORDS: Coronagraphy, Iterated function systems, Near infrared, Optical design, Spectral resolution, Telescopes, Sensors, Channel projecting optics, Exoplanets, Cameras

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Proceedings Article | 21 August 2018 Presentation + Paper

High-contrast imager for complex aperture telescopes (HiCAT): 5. first results with segmented-aperture coronagraph and wavefront control

Rémi Soummer, Gregory Brady, Keira Brooks, Thomas Comeau, Élodie Choquet, Tom Dillon, Sylvain Egron, Rob Gontrum, John Hagopian, Iva Laginja, Lucie Leboulleux, Marshall Perrin, Peter Petrone, Laurent Pueyo, Johan Mazoyer, Mamadou N'Diaye, A. J. Eldorado Riggs, Ron Shiri, Anand Sivaramakrishnan, Kathryn St. Laurent, Ana-Maria Valenzuela, Neil Zimmerman

Proceedings Volume 10698, 106981O (2018) https://doi.org/10.1117/12.2314110

KEYWORDS: Coronagraphy, Space telescopes, Wavefronts, Telescopes, Metrology, Phase retrieval, Carbon nanotubes

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Segmented telescopes are a possible approach to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the increased complexity of their aperture geometry, due to the central obstruction, support structures and segment gaps, makes high-contrast imaging very challenging. The High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed was designed to study and develop solutions for such telescope pupils using wavefront control and coronagraphic starlight suppression. The testbed design has the flexibility to enable studies with increasing complexity for telescope aperture geometries starting with off-axis telescopes, then on-axis telescopes with central obstruction and support structures - e.g. the Wide Field Infrared Survey Telescope (WFIRST) - up to on-axis segmented telescopes, including various concepts for a Large UV, Optical, IR telescope (LUVOIR). In the past year, HiCAT has made significant hardware and software updates in order to accelerate the development of the project. In addition to completely overhauling the software that runs the testbed, we have completed several hardware upgrades, including the second and third deformable mirror, and the first custom Apodized Pupil Lyot Coronagraph (APLC) optimized for the HiCAT aperture, which is similar to one of the possible geometries considered for LUVOIR. The testbed also includes several external metrology features for rapid replacement of parts, and in particular the ability to test multiple apodizers readily, an active tip-tilt control system to compensate for local vibration and air turbulence in the enclosure. On the software and operations side, the software infrastructure enables 24/7 automated experiments that include routine calibration tasks and high-contrast experiments. In this communication we present an overview and status update of the project, both on the hardware and software side, and describe the results obtained with APLC wavefront control.

Proceedings Article | 21 August 2018 Paper

Review of high-contrast imaging systems for current and future ground- and space-based telescopes I: coronagraph design methods and optical performance metrics

G. Ruane, A. Riggs, J. Mazoyer, E. Por, M. N’Diaye, E. Huby, P. Baudoz, R. Galicher, E. Douglas, J. Knight, B. Carlomagno, K. Fogarty, L. Pueyo, N. Zimmerman, O. Absil, M. Beaulieu, E. Cady, A. Carlotti, D. Doelman, O. Guyon, S. Haffert, J. Jewell, N. Jovanovic, C. Keller, M. Kenworthy, J. Kuhn, K. Miller, D. Sirbu, F. Snik, J. Kent Wallace, M. Wilby, M. Ygouf

Proceedings Volume 10698, 106982S (2018) https://doi.org/10.1117/12.2312948

KEYWORDS: Coronagraphy, Space telescopes, Signal to noise ratio, Planets, Point spread functions, Stars, Wavefronts, Telescopes, Optical instrument design, Adaptive optics

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Proceedings Article | 21 August 2018 Paper

Apodized Pupil Lyot coronagraphs with arbitrary aperture telescopes: novel designs using hybrid focal plane masks

Mamadou N'Diaye, Kevin Fogarty, Rémi Soummer, Alexis Carlotti, Kjetil Dohlen, Johan Mazoyer, Laurent Pueyo, Kathryn St. Laurent, Neil Zimmerman

Proceedings Volume 10698, 106986A (2018) https://doi.org/10.1117/12.2313225

KEYWORDS: Coronagraphy, Space telescopes, Stars, Planets, Telescopes, Exoplanets, Apodization, Imaging systems, Optical instrument design

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Proceedings Article | 1 August 2018 Paper

WFIRST CGI integral field spectrograph performance and post-processing in the OS6 observing scenario

Maxime Rizzo, Neil Zimmerman, Tyler Groff, John Krist, A.J. Eldorado Riggs, Qian Gong, Avi Mandell, Prabal Saxena, Michael McElwain, Aki Roberge

Proceedings Volume 10698, 106986U (2018) https://doi.org/10.1117/12.2312400

KEYWORDS: Sensors, Signal to noise ratio, Coronagraphy, Planets, Stars, Spectrographs, Calibration, Data modeling, Point spread functions

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Proceedings Article | 1 August 2018 Presentation + Paper

The WFIRST coronagraph instrument: a major step in the exploration of sun-like planetary systems via direct imaging

Bertrand Mennesson, J. Debes, E. Douglas, B. Nemati, C. Stark, J. Kasdin, B. Macintosh, M. Turnbull, M. Rizzo, A. Roberge, N. Zimmerman, K. Cahoy, J. Krist, V. Bailey, J. Trauger, J. Rhodes, L. Moustakas, M. Frerking, F. Zhao, I. Poberezhskiy, R. Demers

Proceedings Volume 10698, 106982I (2018) https://doi.org/10.1117/12.2313861

KEYWORDS: Stars, Coronagraphy, Planets, Imaging systems, Solar system, Clouds, Spatial resolution, Mid-IR, Visible radiation, Exoplanets

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Proceedings Article | 16 July 2018 Paper

Apodized pupil Lyot coronagraphs designs for future segmented space telescopes

Kathryn St. Laurent, Kevin Fogarty, Neil Zimmerman, Mamadou N'Diaye, Christopher Stark, Johan Mazoyer, Anand Sivaramakrishnan, Laurent Pueyo, Stuart Shaklan, Robert Vanderbei, Rémi Soummer

Proceedings Volume 10698, 106982W (2018) https://doi.org/10.1117/12.2313902

KEYWORDS: Coronagraphy, Telescopes, Space telescopes, Optical instrument design, Stars, Mirrors, Exoplanets, Planets, Wavefronts

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Proceedings Article | 10 July 2018 Presentation

Optical design of exo-planet coronagraph, integral field spectrograph, and high resolution spectrometer for LUVOIR study (Conference Presentation)

Qian Gong, Matthew Bolcar, Julie Crooke, Tyler Groff, Avi Mandell, Neil Zimmerman

Proceedings Volume 10698, 1069812 (2018) https://doi.org/10.1117/12.2311879

KEYWORDS: Optical design, Coronagraphy, Spectroscopy, Spectrographs, Signal detection, Space observatories, Exoplanets, Space telescopes, Telescopes, Deformable mirrors

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Proceedings Article | 10 July 2018 Presentation

Modelling exoplanet detection with the LUVOIR coronagraph (Conference Presentation)

Roser Juanola-Parramon, Neil Zimmerman, Maxime Rizzo, Hari Subedi, Giada Arney, Tyler Groff, Laurent Pueyo, Chris Stark, Rémi Soummer, Matthew Bolcar, Aki Roberge

Proceedings Volume 10698, 1069810 (2018) https://doi.org/10.1117/12.2312837

KEYWORDS: Coronagraphy, Exoplanetary science, Modeling, Stars, Wavefronts, Spectral models, Planetary systems, Tolerancing

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Proceedings Article | 6 July 2018 Presentation + Paper

The large UV/optical/infrared surveyor (LUVOIR): decadal mission study update

Matthew Bolcar, Julie Crooke, Jason Hylan, Ginger Bronke, Christine Collins, James Corsetti, Joe Generie, Qian Gong, Tyler Groff, William Hayden, Andrew Jones, Bryan Matonak, Sang Park, Lia Sacks, Garrett West, Kan Yang, Neil Zimmerman

Proceedings Volume 10698, 106980O (2018) https://doi.org/10.1117/12.2313350

KEYWORDS: Mirrors, Coronagraphy, Near infrared, Observatories, Spectrographs, Imaging systems, Exoplanets

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Proceedings Article | 13 September 2017 Presentation + Paper

The LUVOIR architecture "A" coronagraph instrument

L. Pueyo, N. Zimmerman, M. Bolcar, T. Groff, C. Stark, G. Ruane, J. Jewell, R. Soummer, K. St. Laurent, J. Wang, D. Redding, J. Mazoyer, K. Fogarty, Roser Juanola-Parramon, S. Domagal-Goldman, A. Roberge, O. Guyon, A. Mandell

Proceedings Volume 10398, 103980F (2017) https://doi.org/10.1117/12.2274654

KEYWORDS: Coronagraphy, Wavefronts, Sensors, Planets, Channel projecting optics, Wavefront sensors, Stars, Imaging systems, Mirrors, Telescopes

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In preparation for the Astro 2020 Decadal Survey NASA has commissioned the study four flagship missions spanning to a wide range of observable wavelengths: the Origins Space Telescope (OST, formerly the Far-Infrared Surveyor), Lynx (formerly the X-ray Surveyor), the Large UV/Optical/Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Imager (HabEx). One of the key scientific objectives of the latter two is the detection and characterization of the earth-like planets around nearby stars using the direct imaging technique (along with a broad range of investigations regarding the architecture of and atmospheric composition exoplanetary systems using this technique). As a consequence dedicated exoplanet instruments are being studied for these mission concepts. This paper discusses the design of the coronagraph instrument for the architecture “A” (15 meters aperture) of LUVOIR. The material presented in this paper is aimed at providing an overview of the LUVOIR coronagraph instrument. It is the result of four months of discussions with various community stakeholders (scientists and technologists) regarding the instrument’s basic parameters followed by meticulous design work by the the GSFC Instrument Design Laboratory team. In the first section we review the main science drivers, presents the overall parameters of the instrument (general architecture and backend instrument) and delve into the details of the currently envisioned coronagraph masks along with a description of the wavefront control architecture. Throughout the manuscript we describe the trades we made during the design process. Because the vocation of this study is to provide a baseline design for the most ambitious earth-like finding instrument that could be possibly launched into the 2030’s, we have designed an complex system privileged that meets the ambitious science goals out team was chartered by the LUVOIR STDT exoplanet Working Group. However in an effort to minimize technological risk we tried to maximize the number of technologies that will be matured by the WFIRST coronagraph instruments.

Proceedings Article | 12 September 2017 Presentation + Paper

Current science requirements and planned implementation for the WFIRST-CGI Integral Field Spectrograph (IFS)

Avi Mandell, Tyler Groff, Qian Gong, Maxime Rizzo, Roxana Lupu, Neil Zimmerman, Prabal Saxena, Michael McElwain

Proceedings Volume 10400, 1040009 (2017) https://doi.org/10.1117/12.2274711

KEYWORDS: Iterated function systems, Spectrographs, Planets, Spectral resolution, Exoplanets, Sensors, Prisms, Coronagraphy, Signal to noise ratio, Cameras

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Proceedings Article | 1 September 2017 Paper

Shaped pupil coronagraphy for WFIRST: high-contrast broadband testbed demonstration

Eric Cady, Kunjithapatham Balasubramanian, Jessica Gersh-Range, Jeremy Kasdin, Brian Kern, Raymond Lam, Camilo Mejia Prada, Dwight Moody, Keith Patterson, Ilya Poberezhskiy, A. J. Eldorado Riggs, Byoung-Joon Seo, Fang Shi, Hong Tang, John Trauger, Hanying Zhou, Neil Zimmerman

Proceedings Volume 10400, 104000E (2017) https://doi.org/10.1117/12.2272834

KEYWORDS: Wavefronts, Coronagraphy, Exoplanets, Wavefront sensors, Performance modeling, Systems modeling, Control systems

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Proceedings Article | 1 September 2017 Presentation + Paper

Simulating the WFIRST coronagraph integral field spectrograph

Maxime Rizzo, Tyler Groff, Neil Zimmermann, Qian Gong, Avi Mandell, Prabal Saxena, Michael McElwain, Aki Roberge, John Krist, A. J. Eldorado Riggs, Eric Cady, Camilo Mejia Prada, Timothy Brandt, Ewan Douglas, Kerri Cahoy

Proceedings Volume 10400, 104000B (2017) https://doi.org/10.1117/12.2273066

KEYWORDS: Iterated function systems, Spectrographs, Device simulation, Exoplanets, Atmospheric sciences, Planets, Stars, Cameras, Speckle, Wavefronts

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Proceedings Article | 1 September 2017 Paper

Shaped pupil coronagraph design improvements for the WFIRST coronagraph instrument

A. J. Eldorado Riggs, Neil Zimmerman, Bijan Nemati, John Krist

Proceedings Volume 10400, 104000O (2017) https://doi.org/10.1117/12.2274437

KEYWORDS: Exoplanets, Planets, Diffraction, Monochromatic aberrations, Tolerancing, Interferometry

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Proceedings Article | 1 September 2017 Presentation + Paper

Wavefront control methods for high-contrast integral field spectroscopy

Tyler Groff, Camilo Mejia Prada, Eric Cady, Maxime Rizzo, Avi Mandell, Qian Gong, Michael McElwain, Neil Zimmerman, Prabal Saxena, Olivier Guyon

Proceedings Volume 10400, 104000Q (2017) https://doi.org/10.1117/12.2274709

KEYWORDS: Iterated function systems, Wavefronts, Exoplanets, Imaging spectroscopy, Spectrographs, High angular resolution imaging, Space telescopes, Field spectroscopy, Spectroscopes

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Proceedings Article | 29 July 2016 Paper

Lyot coronagraph design study for large, segmented space telescope apertures

Neil Zimmerman, Mamadou N'Diaye, Kathryn St. Laurent, Rémi Soummer, Laurent Pueyo, Christopher Stark, Anand Sivaramakrishnan, Marshall Perrin, Robert Vanderbei, N. Kasdin, Stuart Shaklan, Alexis Carlotti

Proceedings Volume 9904, 99041Y (2016) https://doi.org/10.1117/12.2233205

KEYWORDS: Space telescopes, Image segmentation, Exoplanets, Optical instrument design, Telescopes, Image segmentation, Coronagraphy, Point spread functions, Tolerancing, Binary data, Apodization

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Proceedings Article | 29 July 2016 Paper

Data processing and algorithm development for the WFIRST coronagraph: comparison of RDI and ADI strategies and impact of spatial sampling on post-processing

Marie Ygouf, Neil Zimmerman, Laurent Pueyo, Rémi Soummer, Marshall Perrin, Bertrand Mennesson, John Krist, Gautam Vasisht, Bijan Nemati, Bruce Macintosh

Proceedings Volume 9904, 99045M (2016) https://doi.org/10.1117/12.2231581

KEYWORDS: Exoplanets, Point spread functions, Space telescopes, Telescopes, Point spread functions, Stars, Algorithm development, Coronagraphy, Speckle, Planets, Iterated function systems

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Direct detection and characterization of mature giant or sub-Neptune exoplanets in the visible will require space- based instruments optimized for high-contrast imaging with contrasts of 10^-9. In this context, the coronagraph instrument (CGI) on the Wide-Field Infrared Survey Telescope (WFIRST) will reach raw contrasts of about 10^-8 or better using state-of-the-art starlight suppression and wavefront control techniques. A ten-fold contrast improvement is therefore required using post-processing techniques in order to detect 10^-9 planets from speckles. Post-processing techniques that are successful on both ground-based and space-based instruments need to be validated at such high contrast levels. In this communication, we investigate speckle subtraction techniques for different observation strategies and hardware parameters on WFIRST-like simulated images in the presence of deformable mirrors and an hybrid lyot coronagraph (HLC). We compare the contrast gain after post-processing in both speckle-noise and photon-noise dominated regimes for two different observing scenarios: the reference star differential imaging (RDI) and the angular differential imaging (ADI). We find that the ADI observing strategy is more robust to speckle and photon noises than the RDI observing strategy, enabling up to a threefold gain with respect to the latter. Thus, we recommend that the telescope be able to roll by at least 13° off nominal. We investigated the impact of spatial sampling on post-processed sensitivity, in the context of design trade studies for the Integral Field Spectrograph (IFS) component of the instrument. Our preliminary results suggest that the spatial sampling can be halved from the baseline sampling rate (~4 lenslets per λ/D) without any degradation in final contrast, thereby reducing the integration time required for spectroscopic characterization. In the speckle-noise dominated regime, we also find that at Nyquist sampling or higher, sub-pixel reference- to-target offsets have a negligible impact on the level of residual speckles after post-processing.

Proceedings Article | 29 July 2016 Paper

Sparse aperture mask wavefront sensor testbed results

Hari Subedi, Neil Zimmerman, N. Jeremy Kasdin, A. J. Riggs

Proceedings Volume 9904, 990464 (2016) https://doi.org/10.1117/12.2232015

KEYWORDS: Wavefront sensors, Space telescopes, Relays, Coronagraphy, Monochromatic aberrations, Error analysis, Actuators, Sensors, Telescopes, Wavefronts

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Proceedings Article | 19 July 2016 Paper

Preparing for JWST wavefront sensing and control operations

Marshall Perrin, D. Scott Acton, Charles-Philippe Lajoie, J. Scott Knight, Matthew Lallo, Marsha Allen, Wayne Baggett, Elizabeth Barker, Thomas Comeau, Eric Coppock, Bruce Dean, George Hartig, William Hayden, Margaret Jordan, Alden Jurling, Trey Kulp, Joseph Long, Michael McElwain, Luis Meza, Edmund Nelan, Remi Soummer, John Stansberry, Christopher Stark, Randal Telfer, Andria Welsh, Thomas Zielinski, Neil Zimmerman

Proceedings Volume 9904, 99040F (2016) https://doi.org/10.1117/12.2233104

KEYWORDS: James Webb Space Telescope, Wavefront sensors, Space telescopes, Observatories, Image segmentation, Stars, Point spread functions, Wavefronts, Space operations, Mirrors

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SPIE Journal Paper | 14 January 2016 Open Access

Shaped pupil Lyot coronagraphs: high-contrast solutions for restricted focal planes

Neil Zimmerman, A. J. Eldorado Riggs, N. Jeremy Kasdin, Alexis Carlotti, Robert Vanderbei

JATIS, Vol. 2, Issue 01, 011012, (January 2016) https://doi.org/10.1117/12.10.1117/1.JATIS.2.1.011012

KEYWORDS: Coronagraphy, Telescopes, Point spread functions, Surface plasmons, Space telescopes, Exoplanets, Planets, Stars, Optical instrument design, Tolerancing

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SPIE Journal Paper | 7 December 2015

WFIRST-AFTA coronagraph shaped pupil masks: design, fabrication, and characterization

Kunjithapatham Balasubramanian, Victor White, Karl Yee, Pierre Echternach, Richard Muller, Matthew Dickie, Eric Cady, Camilo Prada, Daniel Ryan, Ilya Poberezhskiy, Brian Kern, Hanying Zhou, John Krist, Bijan Nemati, A. J. Eldorado Riggs, Neil Zimmerman, N. Jeremy Kasdin

JATIS, Vol. 2, Issue 01, 011005, (December 2015) https://doi.org/10.1117/12.10.1117/1.JATIS.2.1.011005

KEYWORDS: Photomasks, Silicon, Coronagraphy, Reflectivity, Semiconducting wafers, Aluminum, Point spread functions, Wavefronts, Optical instrument design, Etching

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SPIE Journal Paper | 28 October 2015

Demonstration of high contrast with an obscured aperture with the WFIRST-AFTA shaped pupil coronagraph

Eric Cady, Camilo Mejia Prada, Xin An, Kunjithapatham Balasubramanian, Rosemary Diaz, N. Jeremy Kasdin, Brian Kern, Andreas Kuhnert, Bijan Nemati, Ilya Poberezhskiy, A. J. Eldorado Riggs, Robert Zimmer, Neil Zimmerman

JATIS, Vol. 2, Issue 01, 011004, (October 2015) https://doi.org/10.1117/12.10.1117/1.JATIS.2.1.011004

KEYWORDS: Coronagraphy, Photomasks, Planets, Point spread functions, Telescopes, Infrared telescopes, Semiconducting wafers, Reflectivity, Wavefronts, Data modeling

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The coronagraph instrument on the Wide-Field Infrared Survey Telescope-Astrophysics-Focused Telescope Asset (WFIRST-AFTA) mission study has two coronagraphic architectures, shaped pupil and hybrid Lyot, which may be interchanged for use in different observing scenarios. Each architecture relies on newly developed mask components to function in the presence of the AFTA aperture, and so both must be matured to a high technology readiness level in advance of the mission. A series of milestones were set to track the development of the technologies required for the instrument; we report on completion of WFIRST-AFTA coronagraph milestone 2—a narrowband 10−8 contrast test with static aberrations for the shaped pupil—and the plans for the upcoming broadband coronagraph milestone 5.

Proceedings Article | 5 October 2015

Nanofabrication of ultra-low reflectivity black silicon surfaces and devices (Presentation Recording)

Victor White, Karl Yee, Kunjithapatham Balasubramanian, Pierre Echternach, Richard Muller, Matthew Dickie, Eric Cady, Daniel Ryan, Michael Eastwood, Byron van Gorp, A. J. Eldorado Riggs, Niel Zimmerman, N. Jeremy Kasdin

Proceedings Volume 9556, 955609 (2015) https://doi.org/10.1117/12.2189216

KEYWORDS: Reflectivity, Nanofabrication, Silicon, Optical components, Visible radiation, Coronagraphy, Spectrometers, Aerospace engineering, Nanotechnology, Infrared radiation

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Optical devices with features exhibiting ultra low reflectivity on the order of 10-7 specular reflectance in the visible spectrum are required for coronagraph instruments and some spectrometers employed in space research. Nanofabrication technologies have been developed to produce such devices with various shapes and feature dimensions to meet these requirements. Infrared reflection is also suppressed significantly with chosen wafers and processes. Particularly, devices with very high (>0.9) and very low reflectivity (<10-7) on adjacent areas have been fabricated and characterized. Significantly increased surface area due to the long needle like nano structures also provides some unique applications in other technology areas. We present some of the approaches, challenges and achieved results in producing and characterizing such devices currently employed in laboratory testbeds and instruments.

Proceedings Article | 16 September 2015

Sparse aperture mask for low order wavefront sensing

Hari Subedi, Neil Zimmerman, N. Jeremy Kasdin, Kathleen Cavanagh, A. J. Riggs

Proceedings Volume 9605, 96051W (2015) https://doi.org/10.1117/12.2187685

KEYWORDS: Wavefront sensors, Coronagraphy, Sensors, Monochromatic aberrations, Error analysis, Wavefronts, Exoplanets, Space telescopes, Signal to noise ratio, Wavefront aberrations

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A high contrast is required for direct imaging of exoplanets. Ideally, the level of contrast required for direct imaging of exoplanets can be achieved by coronagraphic imaging, but in practice, the contrast is degraded by wavefront aberrations. To achieve the required contrast, low-order wavefront aberrations such as tip-tilt, defocus and coma must be determined and corrected. In this paper, we present a technique that integrates a sparse- aperture mask (SAM) with a shaped pupil coronagraph (SPC) to make precise estimates of these low-order aberrations. Starlight rejected by the coronagraph's focal plane stop is collimated to a relay pupil, where the mask forms an interference fringe pattern on a detector. Using numerical simulations, we show that the SAM can estimate rapidly varying tip-tilt errors in space telescopes arising from line-of-sight pointing oscillations as well as other higher-order modes. We also show that a Kalman filter can be used with the SAM to improve the estimation. At Princetons High Contrast Imaging Laboratory, we have recently created a testbed devoted to low-order wavefront sensing experiments. The testbed incorporates custom-fabricated masks (shaped pupil, focal plane, and sparse aperture) with a deformable mirror and a CCD camera to demonstrate the estimation and correction of low-order aberrations. Our first experiments aim to replicate the results of the SAM wavefront sensor (SAM WFS) Fourier propagation models.

Proceedings Article | 16 September 2015

Exoplanet coronagraph shaped pupil masks and laboratory scale star shade masks: design, fabrication and characterization

Kunjithapatham Balasubramanian, Victor White, Karl Yee, Pierre Echternach, Richard Muller, Matthew Dickie, Eric Cady, Camilo Mejia Prada, Daniel Ryan, Ilya Poberezhskiy, Hanying Zhou, Brian Kern, A. J. Riggs, Neil Zimmerman, Dan Sirbu, Stuart Shaklan, Jeremy Kasdin

Proceedings Volume 9605, 96050L (2015) https://doi.org/10.1117/12.2188954

KEYWORDS: Photomasks, Silicon, Reflectivity, Aluminum, Coronagraphy, Semiconducting wafers, Stars, Wavefronts, Point spread functions, Telescopes

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Star light suppression technologies to find and characterize faint exoplanets include internal coronagraph instruments as well as external star shade occulters. Currently, the NASA WFIRST-AFTA mission study includes an internal coronagraph instrument to find and characterize exoplanets. Various types of masks could be employed to suppress the host star light to about 10^-9 level contrast over a broad spectrum to enable the coronagraph mission objectives. Such masks for high contrast internal coronagraphic imaging require various fabrication technologies to meet a wide range of specifications, including precise shapes, micron scale island features, ultra-low reflectivity regions, uniformity, wave front quality, achromaticity, etc. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks by combining electron beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each, highlighting milestone accomplishments from the High Contrast Imaging Testbed (HCIT) at JPL and from the High Contrast Imaging Lab (HCIL) at Princeton University. We also present briefly the technologies applied to fabricate laboratory scale star shade masks.

Proceedings Article | 16 September 2015

Laboratory performance of the shaped pupil coronagraphic architecture for the WFIRST/AFTA coronagraph

Eric Cady, Camilo Mejia Prada, Xin An, Kunjithapatham Balasubramanian, Rosemary Diaz, N. Jeremy Kasdin, Brian Kern, Andreas Kuhnert, Bijan Nemati, Keith Patterson, Ilya Poberezhskiy, A. J. Eldorado Riggs, Daniel Ryan, Hanying Zhou, Robert Zimmer, Neil Zimmerman

Proceedings Volume 9605, 96050B (2015) https://doi.org/10.1117/12.2189113

KEYWORDS: Coronagraphy, Photomasks, Telescopes, Point spread functions, Microscopes, Infrared telescopes, Silicon, Binary data, Infrared radiation, Stars

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One of the two primary architectures being tested for the WFIRST-AFTA coronagraph instrument is the shaped pupil coronagraph, which uses a binary aperture in a pupil plane to create localized regions of high contrast in a subsequent focal plane. The aperture shapes are determined by optimization, and can be designed to work in the presence of secondary obscurations and spiders - an important consideration for coronagraphy with WFIRST-AFTA. We present the current performance of the shaped pupil testbed, including the results of AFTA Milestone 2, in which ≈ 6 × 10^-9 contrast was achieved in three independent runs starting from a neutral setting.

Proceedings Article | 16 September 2015

Shaped pupil Lyot coronagraph designs for WFIRST/AFTA

Neil Zimmerman, A.J. Eldorado Riggs, N. Jeremy Kasdin, Alexis Carlotti, Robert Vanderbei

Proceedings Volume 9605, 96050A (2015) https://doi.org/10.1117/12.2187141

KEYWORDS: Coronagraphy, Point spread functions, Telescopes, Exoplanets, Binary data, Mirrors, Wavefronts, Space telescopes, Tolerancing, Surface plasmons

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The baseline design for the WFIRST-AFTA Coronagraphic Instrument includes several shaped pupil masks. Our newest designs incorporate the shaped pupil into a Lyot-style architecture to access smaller inner working angles at a given tradeoff in throughput and contrast. We describe two mask configurations: a characterization mode for spectroscopy of exoplanet atmospheres, and a wider-field mode for debris disk observations. We use polychromatic contrast constraints to anchor the spatial extent of the dark search region over the instrument filter bandpass. We examine several practical issues that arise during the optimization process, such as the use of symmetry, and the choice of spatial and wavelength resolutions in the propagation model. Finally, we evaluate the tolerances of the new designs to mask translation and clocking errors.

SPIE Journal Paper | 12 June 2015

Coronagraph-integrated wavefront sensing with a sparse aperture mask

Hari Subedi, Neil Zimmerman, N. Jeremy Kasdin, Kathleen Cavanagh, A. J. Eldorado Riggs

JATIS, Vol. 1, Issue 03, 039001, (June 2015) https://doi.org/10.1117/12.10.1117/1.JATIS.1.3.039001

KEYWORDS: Coronagraphy, Wavefronts, Sensors, Wavefront sensors, Error analysis, Point spread functions, Monochromatic aberrations, Exoplanets, Charge-coupled devices, Wave propagation

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Stellar coronagraph performance is highly sensitive to optical aberrations. In order to effectively suppress starlight for exoplanet imaging applications, low-order wavefront aberrations entering a coronagraph, such as tip-tilt, defocus, and coma, must be determined and compensated. Previous authors have established the utility of pupil-plane masks (both nonredundant/sparse-aperture and generally asymmetric aperture masks) for wavefront sensing (WFS). Here, we show how a sparse aperture mask (SAM) can be integrated with a coronagraph to measure low-order differential phase aberrations. Starlight rejected by the coronagraph’s focal plane stop is collimated to a relay pupil, where the mask forms an interference fringe pattern on a subsequent detector. Our numerical Fourier propagation models show that the information encoded in the fringe intensity distortions is sufficient to accurately discriminate and estimate Zernike phase modes extending from tip-tilt up to radial degree n=5, with amplitude up to λ/20 RMS. The SAM sensor can be integrated with both Lyot and shaped pupil coronagraphs at no detriment to the science beam quality. We characterize the reconstruction accuracy and the performance under low flux/short exposure time conditions, and place it in context of other coronagraph WFS schemes.

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Proceedings Article | 28 August 2014

Shaped pupil design for future space telescopes

A. J. Eldorado Riggs, Neil Zimmerman, Alexis Carlotti, N. Jeremy Kasdin, Robert Vanderbei

Proceedings Volume 9143, 914325 (2014) https://doi.org/10.1117/12.2056371

KEYWORDS: Surface plasmons, Coronagraphy, Point spread functions, Exoplanets, Space telescopes, Manufacturing, Optical instrument design, Telescopes, Reflectivity, Mirrors

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Several years ago at Princeton we invented a technique to optimize shaped pupil (SP) coronagraphs for any telescope aperture. In the last year, our colleagues at the Jet Propulsion Laboratory (JPL) invented a method to produce these non-freestanding mask designs on a substrate. These two advances allowed us to design SPs for two possible space telescopes for the direct imaging of exoplanets and disks, WFIRST-AFTA and Exo-C. In December 2013, the SP was selected along with the hybrid Lyot coronagraph for placement in the AFTA coronagraph instrument. Here we describe our designs and analysis of the SPs being manufactured and tested in the High Contrast Imaging Testbed at JPL.We also explore hybrid SP coronagraph designs for AFTA that would improve performance with minimal or no changes to the optical layout. These possibilities include utilizing a Lyot stop after the focal plane mask or applying large, static deformations to the deformable mirrors (nominally for wavefront correction) already in the system.

Proceedings Article | 7 August 2014

Integration and bench testing for the GRAVITY Coudé IR adaptive optics (CIAO) wavefront sensor

C. Deen, P. Yang, A. Huber, M. Suarez-Valles, S. Hippler, W. Brandner, E. Gendron, Y. Clénet, S. Kendrew, A. Glauser, R. Klein, W. Laun, R. Lenzen, U. Neumann, J. Panduro, J. Ramos, R.-R. Rohloff, A. Salzinger, N. Zimmerman, T. Henning, K. Perraut, G. Perrin, C. Straubmeier, A. Amorim, F. Eisenhauer

Proceedings Volume 9148, 91482T (2014) https://doi.org/10.1117/12.2055127

KEYWORDS: Adaptive optics, Sensors, Wavefront sensors, Computing systems, Mirrors, Real-time computing, Infrared radiation, Infrared sensors, Deformable mirrors, Telescopes

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GRAVITY, a second generation instrument for the Very Large Telescope Interferometer (VLTI), will provide an astrometric precision of order 10 micro-arcseconds, an imaging resolution of 4 milli-arcseconds, and low/medium resolution spectro-interferometry. These improvements to the VLTI represent a major upgrade to its current infrared interferometric capabilities, allowing detailed study of obscured environments (e.g. the Galactic Center, young dusty planet-forming disks, dense stellar cores, AGN, etc...). Crucial to the final performance of GRAVITY, the Coudé IR Adaptive Optics (CIAO) system will correct for the effects of the atmosphere at each of the VLT Unit Telescopes. CIAO consists of four new infrared Shack-Hartmann wavefront sensors (WFS) and associated real-time computers/software which will provide infrared wavefront sensing from 1.45-2.45 microns, allowing AO corrections even in regions where optically bright reference sources are scarce. We present here the latest progress on the GRAVITY wavefront sensors. We describe the adaptation and testing of a light-weight version of the ESO Standard Platform for Adaptive optics Real Time Applications (SPARTA-Light) software architecture to the needs of GRAVITY. We also describe the latest integration and test milestones for construction of the initial wave front sensor.

Proceedings Article | 6 August 2014

Methods for the detection and the characterization of low mass companions using the IFS of SPHERE

A. Zurlo, D. Mesa, R. Gratton, R. Claudi, S. Desidera, E. Giro, J.-L. Beuzit, K. Dohlen, D. Mouillet, P. Puget, F. Wildi, M. Feldt, O. Moeller-Nilsson, A. Baruffolo, D. Fantinel, B. Salasnich, M. Kasper, A. Costille, J.-F. Sauvage, A. Vigan, C. Moutou, M. Langlois, J. Antichi, A. Pavlov, N. Zimmerman, M. Turatto

Proceedings Volume 9147, 914770 (2014) https://doi.org/10.1117/12.2055085

KEYWORDS: Planets, Iterated function systems, Stars, Principal component analysis, Optical spheres, Photometry, Point spread functions, Speckle pattern, Device simulation, Telescopes

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SPHERE is an instrument aimed to the search for low mass companions around young stars in the solar neighborhood. To achieve this goal light from the host star (and in particular the speckle pattern due to the telescope aberrations) should be strongly attenuated while avoiding to cancel out the light from the faint companion. Different techniques can be used to fulfill this aim exploiting the multi-wavelength datacube produced by the Integral Field Spectrograph that is one of the scientific modules that composes SPHERE. In particular we have tested the application of the Spectral Deconvolution and of the Principal Components Analysis techniques. Both of them allow us to obtained a contrast better than 10−5 with respect to the central star at separations of the order of 0.4 arcsec. A further improvement of one order of magnitude can be obtained by combining one of these techniques to the Angular Differential Imaging. To investigate the expected performance of IFS in characterizing detected objects we injected in laboratory data synthetics planets with different intrinsic fluxes and projected separations from the host star. We performed a complete astrometric and photometric analysis of these images to evaluate the expected errors on these measurements, the spectral fidelity and the differences between the reduction methods. The main issue is to avoid the strong self-cancellation that is inherent to all the reduction methods. We have in particular tested two possible solutions: the use of a mask during the reduction on the positions of the companions or, alternatively, using a KLIP procedure for the IFS. This latter seems to give better results in respect o the classical PCA, allowing us to obtain a good spectral reconstruction for simulated objects down to a contrast of ~10^-5.

Proceedings Article | 2 August 2014

Technology development towards WFIRST-AFTA coronagraph

Ilya Poberezhskiy, Feng Zhao, Xin An, Kunjithapatham Balasubramanian, Ruslan Belikov, Eric Cady, Richard Demers, Rosemary Diaz, Qian Gong, Brian Gordon, Renaud Goullioud, Frank Greer, Olivier Guyon, Michael Hoenk, N. Jeremy Kasdin, Brian Kern, John Krist, Andreas Kuhnert, Michael McElwain, Bertrand Mennesson, Dwight Moody, Richard Muller, Bijan Nemati, Keith Patterson, A. J. Riggs, Daniel Ryan, Byoung-Joon Seo, Stuart Shaklan, Erkin Sidick, Fang Shi, Nicholas Siegler, Rémi Soummer, Hong Tang, John Trauger, J. Kent Wallace, Xu Wang, Victor White, Daniel Wilson, Karl Yee, Hanying Zhou, Neil Zimmerman

Proceedings Volume 9143, 91430P (2014) https://doi.org/10.1117/12.2060320

KEYWORDS: Coronagraphy, Sensors, Wavefronts, Wavefront sensors, Iterated function systems, Photomasks, Space telescopes, Exoplanets, Deformable mirrors, Planets

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NASA’s WFIRST-AFTA mission concept includes the first high-contrast stellar coronagraph in space. This coronagraph will be capable of directly imaging and spectrally characterizing giant exoplanets similar to Neptune and Jupiter, and possibly even super-Earths, around nearby stars. In this paper we present the plan for maturing coronagraph technology to TRL5 in 2014-2016, and the results achieved in the first 6 months of the technology development work. The specific areas that are discussed include coronagraph testbed demonstrations in static and simulated dynamic environment, design and fabrication of occulting masks and apodizers used for starlight suppression, low-order wavefront sensing and control subsystem, deformable mirrors, ultra-low-noise spectrograph detector, and data post-processing.

Proceedings Article | 21 July 2014

High contrast imaging at the LBT: the LEECH exoplanet imaging survey

Andrew Skemer, Philip Hinz, Simone Esposito, Michael Skrutskie, Denis Defrère, Vanessa Bailey, Jarron Leisenring, Daniel Apai, Beth Biller, Mickaël Bonnefoy, Wolfgang Brandner, Esther Buenzli, Laird Close, Justin Crepp, Robert De Rosa, Silvano Desidera, Josh Eisner, Jonathan Fortney, Thomas Henning, Karl-Heinz Hofmann, Taisiya Kopytova, Anne-Lise Maire, Jared Males, Rafael Millan-Gabet, Katie Morzinski, Apurva Oza, Jenny Patience, Abhijith Rajan, George Rieke, Dieter Schertl, Joshua Schlieder, Kate Su, Amali Vaz, Kimberly Ward-Duong, Gerd Weigelt, Charles Woodward, Neil Zimmerman

Proceedings Volume 9148, 91480L (2014) https://doi.org/10.1117/12.2057277

KEYWORDS: Planets, Stars, Exoplanets, Telescopes, Adaptive optics, Imaging systems, Mirrors, Cameras, Wavefront sensors, Interferometers

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In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its ~130-night campaign from the Large Binocular Telescope (LBT) atop Mt Graham, Arizona. This survey benefits from the many technological achievements of the LBT, including two 8.4-meter mirrors on a single fixed mount, dual adaptive secondary mirrors for high Strehl performance, and a cold beam combiner to dramatically reduce the telescope’s overall background emissivity. LEECH neatly complements other high-contrast planet imaging efforts by observing stars at L’ (3.8 μm), as opposed to the shorter wavelength near-infrared bands (1-2.4 μm) of other surveys. This portion of the spectrum offers deep mass sensitivity, especially around nearby adolescent (~0.1-1 Gyr) stars. LEECH’s contrast is competitive with other extreme adaptive optics systems, while providing an alternative survey strategy. Additionally, LEECH is characterizing known exoplanetary systems with observations from 3-5μm in preparation for JWST.

Proceedings Article | 26 September 2013

Electric field conjugation with the project 1640 coronagraph

Eric Cady, Christoph Baranec, Charles Beichman, Douglas Brenner, Rick Burruss, Justin Crepp, Richard Dekany, David Hale, Lynne Hillenbrand, Sasha Hinkley, E. Robert Ligon, Thomas Lockhart, Ben Oppenheimer, Ian Parry, Laurent Pueyo, Emily Rice, Lewis Roberts, Jennifer Roberts, Michael Shao, Anand Sivaramakrishnan, Remi Soummer, Hong Tang, Tuan Truong, Gautam Vasisht, Fred Vescelus, J. Kent Wallace, Chengxing Zhai, Neil Zimmerman

Proceedings Volume 8864, 88640K (2013) https://doi.org/10.1117/12.2024635

KEYWORDS: Coronagraphy, Wavefronts, Iterated function systems, Stars, Telescopes, Cameras, Sensors, Adaptive optics, Wavefront sensors, Space telescopes

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The Project 1640 instrument on the 200-inch Hale telescope at Palomar Observatory is a coronagraphic instru- ment with an integral eld spectrograph at the back end, designed to nd young, self-luminous planets around nearby stars. To reach the necessary contrast for this, the PALM-3000 adaptive optics system corrects for fast atmospheric speckles, while CAL, a phase-shifting interferometer in a Mach-Zehnder con guration, measures the quasistatic components of the complex electric eld in the pupil plane following the coronagraphic stop. Two additional sensors measure and control low-order modes. These eld measurements may then be combined with a system model and data taken separately using a white-light source internal to the AO system to correct for both phase and amplitude aberrations. Here, we discuss and demonstrate the procedure to maintain a half-plane dark hole in the image plane while the spectrograph is taking data, including initial on-sky performance.

Proceedings Article | 26 September 2013

Estimate low- and high-order wavefront using P1640 calibrator measurements

C. Zhai, G. Vasisht, M. Shao, T. Lockhart, E. Cady, B. Oppenheimer, R. Burruss, J. Roberts, C. Beichman, D. Brenner, J. Crepp, R. Dekany, L. Hillenbrand, S. Hinkley, I. Parry, L. Pueyo, E. Rice, L. Roberts, A. Sivaramakrishnan, R. Soummer, H. Tang, F. Vescelus, K. Wallace, N. Zimmerman

Proceedings Volume 8864, 88640L (2013) https://doi.org/10.1117/12.2024754

KEYWORDS: Wavefronts, Coronagraphy, Error analysis, Calibration, Wavefront aberrations, Spatial frequencies, Monte Carlo methods, Adaptive optics, Atmospheric propagation, Imaging systems

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P1640 high contrast imaging system on the Palomar 200 inch Telescope consists of an apodized-pupil Lyot coronagraph, the PALM-3000 adaptive optics (P3K-AO), and P1640 Calibrator (CAL). Science images are recorded by an integral field spectrograph covering J-H bands for detecting and characterizing stellar companions. With aberrations from atmosphere corrected by the P3K-AO, instrument performance is limited mainly by the quasi-static speckles due to noncommon path wavefront aberrations for the light to propagate to the P3K-AO wavefront sensor and to the coronagraph mask. The non-common path wavefront aberrations are sensed by CAL, which measures the post-coronagraph E-field using interferometry, and can be effectively corrected by offsetting the P3K-AO deformable mirror target position accordingly. Previously, we have demonstrated using CAL measurements to correct high order wavefront aberrations, which is directly connected to the static speckles in the image plane. Low order wavefront, on the other hand, usually of larger amplitudes, causes light to leak through the coronagraph making the whole image plane brighter. Knowledge error in low order wavefront aberrations can also affect the estimation of the high order wavefront. Even though, CAL is designed to sense efficiently high order wavefront aberrations, the low order wavefront front can be inferred with less sensitivity. Here, we describe our method for estimating both low and high order wavefront aberrations using CAL measurements by propagating the post-coronagraph E-field to a pupil before the coronagraph. We present the results from applying this method to both simulated and experiment data.

Proceedings Article | 26 September 2013

Calibrating apodizer fabrication techniques for high-contrast coronagraphs on segmented and monolithic space telescopes

Anand Sivaramakrishnan, Alexandra Greenbaum, G. Lawrence Carr, Randy Smith, Xiaoxiang Xi, Neil Zimmerman

Proceedings Volume 8860, 88600W (2013) https://doi.org/10.1117/12.2024091

KEYWORDS: Synchrotrons, Calibration, Coronagraphy, Fourier transforms, Glasses, Gemini Planet Imager, Mirrors, Light sources, Space telescopes, Apodization

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High contrast imaging can use pupil apodizers to suppress diffracted starlight from a bright source in order to observe its environs. Metallic half-tone dot transmissive apodizers were developed for the Gemini Planet Imager (GPI) and ESO SPHERE coronagraphs for use in the near-IR. Dot sizes on the scale of the wavelength of the light often result in unexpected variations in the optical transmission vs. superficial dot density relation. We measured 5 and 10 micron half-tone microdot screens' transmissions between 550 -1050 nm to prepare to fabricate apodizations that mitigate diffraction by segments gaps and spiders on future large space telescopes. We utilized slow test beams (f/40, f/80) to estimate the on-axis (far-field, or zero-order) transmission of test patches using a Fourier Transform Spectrograph on Beamline U10B at Brookhaven National Laboratory's National Synchrotron Light Source (BNL NSLS). We also modified our previous GPI IR characterization hardware and methods for this experiment. Our measurements show an internal consistency of 0.1% in transmission, a factor of 5 better than our near-IR GPI work on the NSLS U4IR beamline. The systematics of the set-up appeared to limit the absolute calibration for our f/40 data on the 50-patch, maximum Optical Density 3 (OD3), sample. Credible measurements of transmissions down to about 3% transmission were achieved for this sample. Future work on apodizers for obstructed and segmented primary mirror coronagraphs will require configurations that mimic the intended diffractive configurations closely in order to tune apodizer fabrication to any particular application, and measure chromatic effects in representative diffractive regimes. Further experimental refinements are needed to measure the densest test patches which possess transmissions less than a few percent. The new NSLS-II should provide much greater spectral stability of its synchrotron beam, which will improve measurement accuracy and reduce systematics.

Proceedings Article | 13 September 2012

Project 1640: the world's first ExAO coronagraphic hyperspectral imager for comparative planetary science

Ben Oppenheimer, Charles Beichman, Douglas Brenner, Rick Burruss, Eric Cady, Justin Crepp, Lynne Hillenbrand, Sasha Hinkley, E. Ligon, Thomas Lockhart, Ian Parry, Laurent Pueyo, Emily Rice, Lewis Roberts, Jennifer Roberts, Michael Shao, Anand Sivaramakrishnan, Rémi Soummer, Gautam Vasisht, Fred Vescelus, J. Kent Wallace, Chengxing Zhai, Neil Zimmerman

Proceedings Volume 8447, 844720 (2012) https://doi.org/10.1117/12.926419

KEYWORDS: Stars, Adaptive optics, Coronagraphy, Planets, Wavefronts, Speckle, Sensors, Imaging systems, Control systems, Telescopes

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Project 1640, a high-contrast spectral-imaging effort involving a coordinated set of instrumentation and software, built at AMNH, JPL, Cambridge and Caltech, has been commissioned and is fully operational. This novel suite of instrumentation includes a 3388+241-actuator adaptive optics system, an optimized apodized pupil Lyot coronagraph, an integral field spectrograph, and an interferometric calibration wave front sensor. Project 1640 is the first of its kind of instrumentation, designed to image and characterize planetary systems around nearby stars, employing a variety of techniques to break the speckle-noise barrier. It is operational roughly one year before any similar project, with the goal of reaching a contrast of 10^-7 at 1 arcsecond separation. We describe the instrument, highlight recent results, and document on-sky performance at the start of a 3-year, 99-night survey at the Palomar 5-m Hale telescope.

Proceedings Article | 13 September 2012

A first order wavefront estimation algorithm for P1640 calibrator

C. Zhai, G. Vasisht, M. Shao, T. Lockhart, E. Cady, B. Oppenheimer, R. Burruss, J. Roberts, C. Beichman, D. Brenner, J. Crepp, R. Dekany, S. Hinkley, L. Hillenbrand, E. R. Ligon, I. Parry, L. Pueyo, E. Rice, L. Roberts, A. Sivaramakrishnan, R. Soummer, F. Vescelus, K. Wallace, N. Zimmerman

Proceedings Volume 8447, 84476W (2012) https://doi.org/10.1117/12.927015

KEYWORDS: Calibration, Wavefronts, Coronagraphy, Adaptive optics, Actuators, Imaging systems, Cameras, Speckle, Spatial frequencies, Wavefront sensors

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P1640 calibrator is a wavefront sensor working with the P1640 coronagraph and the Palomar 3000 actuator adaptive optics system (P3K) at the Palomar 200 inch Hale telescope. It measures the wavefront by interfering post-coronagraph light with a reference beam formed by low-pass filtering the blocked light from the coronagraph focal plane mask. The P1640 instrument has a similar architecture to the Gemini Planet Imager (GPI) and its performance is currently limited by the quasi-static speckles due to non-common path wavefront errors, which comes from the non-common path for the light to arrive at the AO wavefront sensor and the coronagraph mask. By measuring the wavefront after the coronagraph mask, the non-common path wavefront error can be estimated and corrected by feeding back the error signal to the deformable mirror (DM) of the P3K AO system. Here, we present a first order wavefront estimation algorithm and an instrument calibration scheme used in experiments done recently at Palomar observatory. We calibrate the P1640 calibrator by measuring its responses to poking DM actuators with a sparse checkerboard pattern at different amplitudes. The calibration yields a complex normalization factor for wavefront estimation and establishes the registration of the DM actuators at the pupil camera of the P1640 calibrator, necessary for wavefront correction. Improvement of imaging quality after feeding back the wavefront correction to the AO system demonstrated the efficacy of the algorithm.

Proceedings Article | 12 September 2012

Narrow-angle astrometry with PRIMA

J. Sahlmann, D. Ségransan, A. Mérand, N. Zimmerman, R. Abuter, B. Chazelas, F. Delplancke, T. Henning, A. Kaminski, R. Köhler, R. Launhardt, M. Mohler, F. Pepe, Didier Queloz, A. Quirrenbach, S. Reffert, C. Schmid, N. Schuhler, T. Schulze-Hartung

Proceedings Volume 8445, 84450S (2012) https://doi.org/10.1117/12.926214

KEYWORDS: Stars, Metrology, Planets, Telescopes, Exoplanets, Sensors, Electroluminescent displays, Interferometers, Calibration, Mirrors

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The Extrasolar Planet Search with PRIMA project (ESPRI) aims at characterising and detecting extrasolar planets by measuring the host star's reflex motion using the narrow-angle astrometry capability of the PRIMA facility at the Very Large Telescope Interferometer. A first functional demonstration of the astrometric mode was achieved in early 2011. This marked the start of the astrometric commissioning phase with the purpose of characterising the instrument's performance, which ultimately has to be sufficient for exoplanet detection. We show results obtained from the observation of bright visual binary stars, which serve as test objects to determine the instrument's astrometric precision, its accuracy, and the plate scale. Finally, we report on the current status of the ESPRI project, in view of starting its scientific programme.

Proceedings Article | 12 September 2012

Aperture mask interferometry with an integral field spectrograph

Neil Zimmerman, Anand Sivaramakrishnan, David Bernat, Ben Oppenheimer, Sasha Hinkley, James Lloyd, Peter Tuthill, Douglas Brenner, Ian Parry, Michal Simon, John Krist, Laurent Pueyo

Proceedings Volume 8445, 84452G (2012) https://doi.org/10.1117/12.926204

KEYWORDS: Stars, Adaptive optics, Calibration, Iterated function systems, Telescopes, Spectrographs, Interferometry, Space telescopes, Coronagraphy, Spectroscopy

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A non-redundant pupil mask placed in front of a low-resolution integral field spectrograph (IFS) adds a spectral dimension to high angular resolution imaging behind adaptive optics systems. We demonstrate the first application of this technique, using the spectroscopic binary star system β CrB as our target. The mask and IFS combination enabled us to measure the first low-resolution spectrum of the F3-F5 dwarf secondary component of β CrB, at an angular separation 141 mas from its A5-A7Vp primary star. To record multi-wavelength closure phases, we collected interferograms simultaneously in 23 spectral channels spanning the J and H bands (1.1 μm-1.8 μm), using the Project 1640 IFS behind the 249-channel PalAO adaptive optics system on the Hale telescope at Palomar Observatory. In addition to providing physical information about the source, spectrally resolved mask fringes have the potential to enhance detection limits over single filter observations. While the overall dynamic range of our observation suffers from large systematic calibration errors, the information gleaned from the full channel range improves the dynamic range by a factor of 3 to 4 over the best single channel.

Proceedings Article | 21 July 2010

Gemini Planet Imager coronagraph testbed results

Anand Sivaramakrishnan, Rémi Soummer, Ben Oppenheimer, G. Lawrence Carr, Jacob Mey, Doug Brenner, Charles Mandeville, Neil Zimmerman, Bruce Macintosh, James Graham, Les Saddlemyer, Brian Bauman, Alexis Carlotti, Laurent Pueyo, Peter Tuthill, Christophe Dorrer, Robin Roberts, Alexandra Greenbaum

Proceedings Volume 7735, 773586 (2010) https://doi.org/10.1117/12.858623

KEYWORDS: Coronagraphy, Gemini Planet Imager, Adaptive optics, Wavefronts, Stars, Mirrors, Calibration, Wavefront sensors, Synchrotrons, Gemini Observatory

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The Gemini Planet Imager (GPI) is an extreme AO coronagraphic integral field unit YJHK spectrograph destined for first light on the 8m Gemini South telescope in 2011. GPI fields a 1500 channel AO system feeding an apodized pupil Lyot coronagraph, and a nIR non-common-path slow wavefront sensor. It targets detection and characterizion of relatively young (<2GYr), self luminous planets up to 10 million times as faint as their primary star. We present the coronagraph subsystem's in-lab performance, and describe the studies required to specify and fabricate the coronagraph. Coronagraphic pupil apodization is implemented with metallic half-tone screens on glass, and the focal plane occulters are deep reactive ion etched holes in optically polished silicon mirrors. Our JH testbed achieves H-band contrast below a million at separations above 5 resolution elements, without using an AO system. We present an overview of the coronagraphic masks and our testbed coronagraphic data. We also demonstrate the performance of an astrometric and photometric grid that enables coronagraphic astrometry relative to the primary star in every exposure, a proven technique that has yielded on-sky precision of the order of a milliarsecond.

Proceedings Article | 20 August 2009

Calibrating IR optical densities for the Gemini Planet Imager extreme adaptive optics coronagraph apodizers

Anand Sivaramakrishnan, Rémi Soummer, G. Lawrence Carr, Christophe Dorrer, Allen Bolognesi, Neil Zimmerman, Ben Oppenheimer, Robin Roberts, Alexandra Greenbaum

Proceedings Volume 7440, 74401C (2009) https://doi.org/10.1117/12.826955

KEYWORDS: Coronagraphy, Calibration, Absorbance, Gemini Planet Imager, Opacity, Synchrotrons, Glasses, FT-IR spectroscopy, Adaptive optics, Optical calibration

Read Abstract +

High contrast imaging sometimes uses apodized masks in coronagraphs to suppress diffracted starlight from a bright source in order to observe its environs. Continuously graded opacity material and metallic half-tone dots are two possible apodizers fabrication techniques. In the latter approach if dot sizes are comparable to the wavelength of the light, surface plasmon effects can complicate the optical density (OD) vs. superficial dot density relation. OD can also be a complicated function of wavelength. We measured half-tone microdot screens' and continuous materials' transmissions. Our set-up replicated the f/ 64 optical configuration of the Gemini Planet Imager's Apodized Pupil Lyot Coronagraph pupil plane, where we plan to place our pupil plane masks. Our half-tone samples were fabricated with 2, 5, and 10 micron dot sizes, our continuous greyscale was High Energy Electron Beam Sensitive (HEBS) glass (Canyon Materials Inc.). We present optical density (OD) vs. wavelength curves for our half-tone and continuous greyscale samples 1.1 - 2.5 μm wavelength range. Direct measurements of the beam intensity in the far field using a Fourier Transform Infrared Spectrograph on Beamline U4IR at Brookhaven National Laboratory's National Synchrotron Light Source (NSLS) provided transmission spectra of test patches and apodizers. We report the on-axis IR transmission spectra through screens composed of metallic dots that are comparable in size with the wavelength of the light used, over a range of optical densities. We also measured departures from simple theory describing the array of satellite spots created by thin periodic grids in the pupil of the system. Such spots are used for photometry and astrometry in coronagraphic situations. Our results pertain to both ground and space based coronagraphs that use spatially variable attenuation, typically in focal plane or pupil plane masks.

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