Dr. Anand Sivaramakrishnan Profile

Dr. Anand Sivaramakrishnan

AURA Scientist at Space Telescope Science Institute

SPIE Involvement:

Author | Instructor

Publications (69)

PROCEEDINGS ARTICLE | August 21, 2018

James Webb Space Telescope optical simulation testbed V: wide-field phase retrieval assessment

Proc. SPIE. 10698, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

KEYWORDS: Monochromatic aberrations, Point spread functions, Telescopes, Mirrors, Cameras, Wavefront sensors, Wavefronts, Phase retrieval, Space telescopes, James Webb Space Telescope

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PROCEEDINGS ARTICLE | August 21, 2018

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

Proc. SPIE. 10698, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

KEYWORDS: Telescopes, Metrology, Wavefronts, Coronagraphy, Phase retrieval, Space telescopes, 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.

SPIE Journal Paper | August 17, 2018

Pair-based Analytical model for Segmented Telescopes Imaging from Space for sensitivity analysis

Lucie Leboulleux, Jean-François Sauvage, Laurent Pueyo, Thierry Fusco, Rémi Soummer, Johan Mazoyer, Anand Sivaramakrishnan, Mamadou N’Diaye, Olivier Fauvarque

JATIS Vol. 4 Issue 03

KEYWORDS: Image segmentation, Coronagraphy, Telescopes, Space telescopes, Systems modeling, Error analysis, Monochromatic aberrations, Zernike polynomials, James Webb Space Telescope, Mirrors

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PROCEEDINGS ARTICLE | July 16, 2018

Apodized pupil Lyot coronagraphs designs for future segmented space telescopes

Proc. SPIE. 10698, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

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

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PROCEEDINGS ARTICLE | July 6, 2018

Sensitivity analysis for high-contrast imaging with segmented space telescopes

Proc. SPIE. 10698, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

KEYWORDS: Point spread functions, Telescopes, Mirrors, Segmented mirrors, Error analysis, Computer simulations, Coronagraphy, Exoplanets, Space telescopes, Zernike polynomials

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Direct imaging and spectroscopy of Earth-like planets will require high-contrast imaging at very close angular separation: 1e10 star to planet ux ratio at a few tenths of an arcsecond. Large telescopes in space are necessary to provide sufficient collecting area and angular resolution to achieve this goal. In the static case, coronagraphic instrument designs combined with wavefront control techniques have been optimized for segmented on-axis telescope geometries, but the extreme wavefront stability required at very high contrast of the order of tens of picometers remains one of the main challenges. Indeed, cophasing errors and instabilities directly contribute to the degradation of the final image contrast. A systematic understanding is therefore needed to quantify and optimize the static and dynamic constraints on segment phasing. We present an analytical model: Pair-based Analytical model for Segmented Telescopes Imaging from Space (PASTIS), which enables quasi-instantaneous analytical evaluations of the impact of segment-level aberrations and phasing on the image contrast. This model is based on a multiple sum of Young interference fringes between pairs of segments and produces short and long exposure coronagraphic images with a segmented telescope in presence of local phase aberrations on each segment. PASTIS matches end-to-end numerical simulations with high-fidelity (3% rms error on the contrast). Moreover, the model can be inverted by dint of a projection on the singular modes of the phase to provide constraints on each Zernike polynomial for each segment. These singular modes provide information on the contrast sensitivity to segment-level phasing errors in the pupil, which can be used to derive constraints on both static and dynamic mitigation strategies (e.g. backplane geometry or segment vibration sensing and control). The few most sensitive modes can be well identified and must be controlled at the level of tens of picometers, while the least sensitive modes in the hundreds of picometers. This novel formalism enables a fast and efficient sensitivity analysis for any segmented telescopes, in both static and dynamic modes.

SPIE Journal Paper | January 18, 2018

Automated data processing architecture for the Gemini Planet Imager Exoplanet Survey

Jason J. Wang, Marshall Perrin, Dmitry Savransky, Pauline Arriaga, Jeffrey Chilcote, Robert J. De Rosa, Maxwell Millar-Blanchaer, Christian Marois, Julien Rameau, Schuyler Wolff, Jacob Shapiro, Jean-Baptiste Ruffio, Jérôme Maire, Franck Marchis, James Graham, Bruce Macintosh, S. Mark Ammons, Vanessa Bailey, Travis Barman, Sebastian Bruzzone, Joanna Bulger, Tara Cotten, René Doyon, Gaspard Duchêne, Michael Fitzgerald, Katherine B. Follette, Stephen Goodsell, Alexandra Greenbaum, Pascale Hibon, Li-Wei Hung, Patrick Ingraham, Paul Kalas, Quinn Konopacky, James Larkin, Mark Marley, Stanimir Metchev, Eric Nielsen, Rebecca Oppenheimer, David Palmer, Jennifer Patience, Lisa Poyneer, Laurent Pueyo, Abhijith Rajan, Fredrik Rantakyrö, Adam Schneider, Anand Sivaramakrishnan, Inseok Song, Rémi Soummer, Sandrine Thomas, J. Kent Wallace, Kimberly Ward-Duong, Sloane Wiktorowicz

JATIS Vol. 4 Issue 01

KEYWORDS: Data processing, Gemini Planet Imager, Planets, Calibration, Point spread functions, Stars, Polarimetry, Databases, Exoplanets, Adaptive optics

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PROCEEDINGS ARTICLE | September 5, 2017

James Webb Space Telescope optical simulation testbed IV: linear control alignment of the primary segmented mirror

Proc. SPIE. 10398, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VIII

KEYWORDS: Telescopes, Mirrors, Segmented mirrors, Wavefront sensors, Wavefronts, Optical testing, Space telescopes, Optical simulations, Optical alignment, James Webb Space Telescope

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PROCEEDINGS ARTICLE | August 9, 2016

Gemini planet imager observational calibration XII: photometric calibration in the polarimetry mode

Proc. SPIE. 9908, Ground-based and Airborne Instrumentation for Astronomy VI

KEYWORDS: Point spread functions, Stars, Calibration, Satellites, Spectroscopy, Imaging spectroscopy, Polarimetry, Coronagraphy, Photometry, Gemini Planet Imager

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PROCEEDINGS ARTICLE | July 29, 2016

Lyot coronagraph design study for large, segmented space telescope apertures

Proc. SPIE. 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave

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

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PROCEEDINGS ARTICLE | July 29, 2016

In-focus phase retrieval using JWST-NIRISS's non-redundant mask

Proc. SPIE. 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave

KEYWORDS: Point spread functions, Mirrors, Image segmentation, Glasses, Wavefront sensors, Wavefronts, Phase retrieval, Space telescopes, Phase measurement, James Webb Space Telescope

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PROCEEDINGS ARTICLE | September 16, 2015

Astrometric accuracy of aperture making interferometry with JWST-NIRISS

Proc. SPIE. 9605, Techniques and Instrumentation for Detection of Exoplanets VII

KEYWORDS: Point spread functions, Astronomy, Data modeling, Aerospace engineering, Sensors, Interferometry, Exoplanets, Space telescopes, Planets, James Webb Space Telescope

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PROCEEDINGS ARTICLE | August 28, 2014

NIRISS aperture masking interferometry: an overview of science opportunities

Proc. SPIE. 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave

KEYWORDS: Point spread functions, Optical filters, Stars, Interferometry, Exoplanets, Planets, Galactic astronomy, James Webb Space Telescope, Gemini Planet Imager, Bandpass filters

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PROCEEDINGS ARTICLE | August 28, 2014

Non-redundant masking ideas on JWST

Proc. SPIE. 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave

KEYWORDS: Point spread functions, Telescopes, Mirrors, Cameras, Sensors, Image segmentation, Wavefront sensors, Wavefronts, Space telescopes, James Webb Space Telescope

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PROCEEDINGS ARTICLE | August 28, 2014

Updated point spread function simulations for JWST with WebbPSF

Proc. SPIE. 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave

KEYWORDS: Point spread functions, Telescopes, Spectroscopy, Wavefront sensors, Wavefronts, Coronagraphy, Spectroscopes, James Webb Space Telescope, Device simulation, Instrument modeling

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PROCEEDINGS ARTICLE | August 28, 2014

Fizeau interferometric cophasing of segmented mirrors

Proc. SPIE. 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave

KEYWORDS: Point spread functions, Telescopes, Mirrors, Segmented mirrors, Image segmentation, Interferometry, Wavefronts, Numerical simulations, Space telescopes, James Webb Space Telescope

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PROCEEDINGS ARTICLE | August 7, 2014

The Gemini planet imager: first light and commissioning

Proc. SPIE. 9148, Adaptive Optics Systems IV

KEYWORDS: Telescopes, Stars, Gemini Observatory, Calibration, Wavefront sensors, Adaptive optics, Coronagraphy, Planets, Iterated function systems, Gemini Planet Imager

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PROCEEDINGS ARTICLE | August 2, 2014

Analyzing the first JWST-NIRISS NRM test data

Proc. SPIE. 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave

KEYWORDS: Point spread functions, Data modeling, Sensors, Interferometry, Capacitance, Space telescopes, Phase measurement, Infrared telescopes, James Webb Space Telescope, Visibility

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PROCEEDINGS ARTICLE | July 28, 2014

Gemini planet imager observational calibrations VI: photometric and spectroscopic calibration for the integral field spectrograph