Dr. Alexandra Z. Greenbaum Profile

Dr. Alexandra Z. Greenbaum

at Caltech

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Author

Publications (5)

SPIE Journal Paper | 20 September 2024 Open Access

Current laboratory performance of starlight suppression systems and potential pathways to desired Habitable Worlds Observatory exoplanet science capabilities

Bertrand Mennesson, Ruslan Belikov, Emiel Por, Eugene Serabyn, Garreth Ruane, A. J. Eldorado Riggs, Dan Sirbu, Laurent Pueyo, Rémi Soummer, Jeremy Kasdin, Stuart Shaklan, Byoung-Joon Seo, Christopher Stark, Eric Cady, Pin Chen, Brendan Crill, Kevin Fogarty, Alexandra Greenbaum, Olivier Guyon, Roser Juanola-Parramon, Brian Kern, John Krist, Bruce Macintosh, David Marx, Dimitri Mawet, Camilo Mejia Prada, Rhonda Morgan, Bijan Nemati, Leonid Pogorelyuk, Susan Redmond, Sara Seager, Nicholas Siegler, Karl Stapelfeldt, Sarah Steiger, John Trauger, James Wallace, Marie Ygouf, Neil Zimmerman

JATIS, Vol. 10, Issue 03, 035004, (September 2024) https://doi.org/10.1117/12.10.1117/1.JATIS.10.3.035004

KEYWORDS: Coronagraphy, Planets, Signal to noise ratio, Telescopes, Point spread functions, Stars, Exoplanets, Wavefronts, Spectroscopy, Design

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We summarize the current best polychromatic (∼10% to 20% bandwidth) contrast performance demonstrated in the laboratory by different starlight suppression approaches and systems designed to directly characterize exoplanets around nearby stars. We present results obtained by internal coronagraph and external starshade experimental testbeds using entrance apertures equivalent to off-axis or on-axis telescopes, either monolithic or segmented. For a given angular separation and spectral bandwidth, the performance of each starlight suppression system is characterized by the values of “raw” contrast (before image processing), off-axis (exoplanet) core throughput, and post-calibration contrast (the final 1-sigma detection limit of off-axis point sources, after image processing). Together, the first two parameters set the minimum exposure time required for observations of exoplanets at a given signal-to-noise, i.e., assuming perfect subtraction of background residuals down to the photon noise limit. In practice, residual starlight speckle fluctuations during the exposure will not be perfectly estimated nor subtracted, resulting in a finite post-calibrated contrast and exoplanet detection limit whatever the exposure time. To place the current laboratory results in the perspective of the future Habitable Worlds Observatory (HWO) mission, we simulate visible observations of a fiducial Earth/Sun twin system at 12 pc, assuming a 6 m (inscribed diameter) collecting aperture and a realistic end-to-end optical throughput. The exposure times required for broadband exo-Earth detection (20% bandwidth around λ=0.55 μm) and visible spectroscopic observations (R=70) are then computed assuming various levels of starlight suppression performance, including the values currently demonstrated in the laboratory. Using spectroscopic exposure time as a simple metric, our results point to key starlight suppression system design performance improvements and trades to be conducted in support of HWO’s exoplanet science capabilities. These trades may be explored via numerical studies, lab experiments, and high-contrast space-based observations and demonstrations.

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Proceedings Article | 23 August 2024 Paper

The Roman coronagraph community participation program: data reduction and simulations

Maxwell Andrew Millar-Blanchaer, Jason Wang, Ellis Bogat, Jürgen Schreiber, Marie Ygouf, Kevin Ludwick, Alexandra Greenbaum, Vanessa Bailey, Sergi Hildebrandt Rafels, Dmitry Savransky, Matthias Samland, Lisa Altinier, Ramya Anche, Beth Biller, Amanda Chavez, Elodie Choquet, Julien Girard, Justin Hom, James Ingalls, N. Jeremy Kasdin, Oliver Krause, John Livingston, Johan Mazoyer, Laurent Pueyo, Taichi Uyama, Robert Zellem, Neil Zimmerman

Proceedings Volume 13092, 1309256 (2024) https://doi.org/10.1117/12.3020478

KEYWORDS: Calibration, Coronagraphy, Simulations, Observational astronomy, Data processing, Exoplanets, Equipment, Analog electronics, Space telescopes, Signal processing

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Proceedings Article | 23 August 2024 Presentation + Paper

The Nancy Grace Roman Space Telescope coronagraph community participation program

Dmitry Savransky, Vanessa Bailey, Schuyler Wolff, Maxwell Millar-Blanchaer, Jason Wang, Lisa Altinier, Ramya Anche, Pierre Baudoz, Beth Biller, Sarah Blunt, Wolfgang Brandner, Marah Brinjikji, Oscar Carrión-González, Amanda Chavez, Elodie Choquet, David Doelman, Julien Girard, Alexandra Greenbaum, Samantha Hasler, Justin Hom, James Ingalls, Stephen Kane, N. Jeremy Kasdin, Oliver Krause, Masayuki Kuzuhara, Alexis Lau, Zhexing Li, John Livingston, Patrick Lowrance, Kevin Ludwick, Bruce Macintosh, Eric Mamajek, Mark Marley, Johan Mazoyer, Bertrand Mennesson, Toshiyuki Mizuki, Sarah Moran, Naoshi Murakami, Jun Nishikawa, Malachi Noel, Laurent Pueyo, Sergi Hildebrandt Rafels, Jason Rhodes, Tyler Robinson, Robert De Rosa, Matthias Samland, Nicholas Schragal, Jürgen Schreiber, Jennifer Sobeck, Karl Stapelfeldt, Motohide Tamura, Taichi Uyajma, Arthur Vigan, Michele Woodland, Marie Ygouf, Kenta Yoneta, Robert Zellem, Neil Zimmerman

Proceedings Volume 13092, 130921I (2024) https://doi.org/10.1117/12.3020514

KEYWORDS: Coronagraphy, Stars, Observatories, Space telescopes, Wavefronts, Telescopes, Planets, Observational astronomy, Exoplanets

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Proceedings Article | 5 October 2023 Poster + Paper

Testing and performance of IFS upgrades for GPI 2.0

Dillon Peng, Jeffrey Chilcote, Quinn Konopacky, Randall Hamper, Joel Burke, Brian Sands, Matthew Engstrom, Abigail Karaszewski, Rebecca Boyle, Mary Anne Limbach, Alexandra Greenbaum, Anand Sivaramakrishnan, Alexa Rizika, Saavidra Perera, Clarissa Do Ó, Jayke Nguyen, Bruce Macintosh, Joeleff Fitzsimmons, Christian Marois, Fredrik Rantakyrö, Arlene Aleman, Jérôme Maire, Robert De Rosa, Emiel Por, Dmitry Savransky, Meiji Nguyen, Marshall Perrin, Remi Soummer, Laurent Pueyo, Bryony Nickson, Eckhart Spalding

Proceedings Volume 12680, 126801Y (2023) https://doi.org/10.1117/12.2677675

KEYWORDS: Prisms, Gemini Planet Imager, Iterated function systems, Optical filters, Spectral resolution, Optical alignment, Gemini Observatory, Design and modelling, Wavefront sensors

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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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