Dr. John G. Hagopian Profile

Dr. John G. Hagopian

Owner/Optical Physicist at Advanced NanoPhotonics Inc

SPIE Involvement:

Author

Publications (64)

Proceedings Article | 23 August 2024 Presentation + Paper

Presentation + Paper

High-contrast imager for complex aperture telescopes (HiCAT): 11. System-level demonstration of the apodized pupil Lyot coronagraph with a segmented aperture in air

Rémi Soummer, Raphaël Pourcelot, Emiel Por, Sarah Steiger, Iva Laginja, Benjamin Buralli, Susan Redmond, Laurent Pueyo, Marshall Perrin, Marc Ferrari, Jules Fowler, John Hagopian, Mamadou N'Diaye, Meiji Nguyen, Bryony Nickson, Peter Petrone, Ananya Sahoo, Anand Sivaramakrishnan, Scott Will

Proceedings Volume 13092, 130921Z (2024) https://doi.org/10.1117/12.3018037

KEYWORDS: Coronagraphy, Telescopes, Imaging systems, Wavefronts, Phase retrieval, Exoplanets

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We present the final results of the Apodized Pupil Lyot Coronagraph (APLC) on the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed, under NASA’s Strategic Astrophysics Technology program. The HiCAT testbed was developed over the past decade to enable a system-level demonstration of coronagraphy for exoplanet direct imaging with the future Habitable Wolds Observatory. HiCAT includes an active, segmented telescope simulator, a coronagraph, and metrology systems (Low-order and Mid-Order Zernike Wavefront Sensors, and Phase Retrieval camera). These results correspond to an off-axis (un-obscured) configuration, as was envisioned in the 2020 Decadal Survey Recommendations. Narrowband and broadband dark holes are generated using two continuous deformable mirrors (DM) to control high order wavefront aberrations, and low-order drifts can be further stabilized using the LOWFS loop. The APLC apodizers, manufactured using carbon nanotubes, were optimized for broadband performance and include the calibrated geometric aperture. The objectives of this SAT program were organized in three milestones to reach a system-like level demonstration of segmented-aperture coronagraphy, from static component demonstration to system-level demonstration under both natural and artificial disturbances. HiCAT is, to this date, the only testbed facility able to demonstrate high-contrast coronagraphy with a truly segmented aperture, as is required for the Habitable World Observatory, albeit limited to ambient conditions, corresponding to NASA’s Technology Readiness Level (TRL) 4. Results presented here include 6 × 10⁻⁸ (90% CI) contrast in 9% bandpass in a 360 deg dark hole with inner and outer working angles of 4.4λ/D_pupil and 11λ/D_pupil. Narrowband contrast (3% bandpass) reaches 2.4 × 10⁻⁸ (90% confidence interval). We first explore the open-loop stability of the entire system quantify the baseline testbed performance. Then we present dark hole stabilization using both high-order and low-order loops under both low-order and segment level drifts in narrow and broadband. We compare experimental data with that obtained by the end-to-end HiCAT simulator. We establish that current performance limitations are due to a combination of ambient conditions, detector and deformable mirrors noises (including quantization), and model mismatch.

Proceedings Article | 6 October 2023 Presentation

Presentation

High-contrast imager for complex aperture telescopes (HiCAT): 10. Broadband Zernike wavefront sensor under natural and artificial drifts

Raphaël Pourcelot, Emiel Por, Mamadou N'Diaye, Benjamin Buralli, Marcel Carbillet, Kjetil Dohlen, Sylvain Egron, Marc Ferrari, Rachel Fox, Rob Gontrum, Iva Laginja, Meiji Nguyen, Bryony Nickson, Marshall Perrin, Peter Petrone, Laurent Pueyo, Susan Redmond, Ananya Sahoo, Anand Sivaramakrishnan, Hari Subedi, Sam Weinstock, Scott Will, Rémi Soummer, John Hagopian

Proceedings Volume 12680, 126801F (2023) https://doi.org/10.1117/12.2677790

KEYWORDS: Wavefront sensors, Telescopes, Imaging systems, Coronagraphy, Deformable mirrors, Stars, Monochromatic aberrations, Image segmentation, Wavefront aberrations, Observatories

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Proceedings Article | 5 October 2023 Presentation + Paper

Presentation + Paper

High contrast spectroscopy testbed (HCST): experimental results with an apodized vortex coronagraph

A. Bertrou-Cantou, J. Llop-Sayson, J. Liberman, D. Mawet, J. G. Hagopian, G. Ruane, A. J. Eldorado Riggs, E. Serabyn

Proceedings Volume 12680, 126801B (2023) https://doi.org/10.1117/12.2677902

KEYWORDS: Coronagraphy, Image segmentation, Apodization, Telescopes, Spectroscopy, Point spread functions, Simulations, Diffraction, Design and modelling, Reflection

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Proceedings Article | 4 October 2023 Presentation + Paper

Presentation + Paper

The Roman Space Telescope optical system: status, test, and verification

Matthew Bolcar, Josh Abel, Lisa Bartusek, Tom Casey, Bente Eegholm, Guangjun Gao, Tyler Groff, John Hagopian, Joseph Howard, Alden Jurling, Gary Kuan, Dave Kubalak, Kuo-Chia (Alice) Liu, Cathy Marx, Kim Mehalick, Mark Melton, Scott Rohrbach, Derek Sabatke, Tony Whitman

Proceedings Volume 12676, 126760O (2023) https://doi.org/10.1117/12.2677569

KEYWORDS: Mirrors, Equipment, Vacuum, Optical alignment, Stray light, Optical fabrication, Metrology, Tunable filters, Telescopes, Space telescopes

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Proceedings Article | 29 August 2022 Poster + Paper

Poster + Paper

GPI 2.0: optical designs for the upgrade of the Gemini Planet Imager coronagraphic system

Meiji N. Nguyen, Bryony F. Nickson, Emiel H. Por, Rémi Soummer, John G. Hagopian, Bruce Macintosh, Jeffrey Chilcote, Laurent Pueyo, Marshall Perrin, Quinn Konopacky

Proceedings Volume 12188, 121884K (2022) https://doi.org/10.1117/12.2630675

KEYWORDS: Gemini Planet Imager, Coronagraphy, Point spread functions, Gemini Observatory, Manufacturing, Optical design, Planetary systems, Observatories, Fourier transforms, Tolerancing

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Proceedings Article | 29 August 2022 Poster

Poster

Prism assembly for Roman Space Telescope Wide Field Instrument slit-less spectroscopy

Bente Eegholm, Catherine Marx, Victor Chambers, Jenny Chu, Jay Voris, Guangjun Gao, John Lehan, Laurie Seide, Bert Pasquale, John Hagopian, Peter Morey, Qian Gong, Evan Bray

Proceedings Volume 12180, 121804X (2022) https://doi.org/10.1117/12.2633674

KEYWORDS: Prisms, Space telescopes, Spectroscopes, Field spectroscopy, Spectral resolution, Optical components, Mirrors, Telescopes, Spectroscopy, Optical instrument design

Proceedings Article | 27 August 2022 Presentation + Paper

Presentation + Paper

Laboratory demonstration of high contrast with the PIAACMC coronagraph on an obstructed and segmented aperture

Ruslan Belikov, Dan Sirbu, David Marx, Camilo Mejia Prada, Eduardo Bendek, Eugene Pluzhnik, Stephen Bryson, Brian Kern, Olivier Guyon, Kevin Fogarty, Justin Knight, Daniel Wilson, John Hagopian

Proceedings Volume 12180, 1218025 (2022) https://doi.org/10.1117/12.2630474

KEYWORDS: Coronagraphy, Stars, Yield improvement, Telescopes, Tolerancing, Wavefronts, Speckle, Modulation, Mirrors, Exoplanets

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Proceedings Article | 27 August 2022 Presentation + Paper

Presentation + Paper

High-contrast imager for complex aperture telescopes (HiCAT): 8. Dark zone demonstration with simultaneous closed-loop low-order wavefront sensing and control

Rémi Soummer, Emiel Por, Raphaël Pourcelot, Susan Redmond, Iva Laginja, Scott Will, Marshall Perrin, Laurent Pueyo, Ananya Sahoo, Peter Petrone, Keira Brooks, Rachel Fox, Alex Klein, Bryony Nickson, Thomas Comeau, Marc Ferrari, Rob Gontrum, John Hagopian, Lucie Leboulleux, Daniel Leongomez, Joe Lugten, Laurent Mugnier, Mamadou N'Diaye, Meiji Nguyen, James Noss, Jean-François Sauvage, Nathan Scott, Anand Sivaramakrishnan, Hari Subedi, Sam Weinstock

Proceedings Volume 12180, 1218026 (2022) https://doi.org/10.1117/12.2630444

KEYWORDS: Coronagraphy, Wavefronts, Wavefront sensors, Telescopes, Phase retrieval

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Proceedings Article | 4 August 2021 Presentation

Presentation

High-contrast imager for complex aperture telescopes (HiCAT): 7. Dark zone demonstration with fully segmented aperture coronagraph

Rémi Soummer, Iva Laginja, Scott Will, Marshall Perrin, James Noss, Emiel Por, Susan Redmond, Raphaël Pourcelot, Ananya Sahoo, Peter Petrone, Keira Brooks, Laurent Pueyo, Bryony Nickson, Matt Maclay, Gregory Brady, Thomas Comeau, Julia Fowler, Kelsey Glazer, Rob Gontrum, John Hagopian, Theo Jolivet, Maggie Kautz, Lucie Leboulleux, Evelyn McChesney, Laurent Mugnier, Mamadou N'Diaye, Meiji Nguyen, Heather Olszewski, Leonid Pogorelyuk, Jaret Prothro, Jean-François Sauvage, Nathan Scott, Ron Shiri, Anand Sivaramakrishnan, Hari Subedi, Sam Weinstock, Yinzi Xin, Rebecca Zhang

Proceedings Volume 11823, 118230T (2021) https://doi.org/10.1117/12.2594684

KEYWORDS: Image segmentation, Coronagraphy, Telescopes, Imaging systems, Wavefront sensors, Wavefronts, Deformable mirrors, Ultraviolet telescopes, Ultraviolet radiation, UV optics

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Proceedings Article | 7 January 2021 Paper

Paper

Parabolic deformable mirror testbed for the ExoSpec project

Hari Subedi, Roser Juanola-Parramon, Tyler Groff, John Hagopian

Proceedings Volume 11443, 114431E (2021) https://doi.org/10.1117/12.2562642

KEYWORDS: Deformable mirrors, Actuators, Exoplanets, Packaging, Coronagraphy, Space operations, Wavefront sensors, Optical components, Computer simulations, Device simulation

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SPIE Journal Paper | 26 December 2020 Open Access

Open Access

Characterization of Nancy Grace Roman Space Telescope slitless spectrometer (grism)

Qian Gong, Matthew Bergkoetter, Joshua Berrier, Victor Chambers, Margaret Dominguez, Wesley Fincher, John Hagopian, Catherine Marx, Laurie Seide

JATIS, Vol. 6, Issue 04, 045008, (December 2020) https://doi.org/10.1117/12.10.1117/1.JATIS.6.4.045008

KEYWORDS: Point spread functions, Diffraction, Spectroscopy, Sensors, Space telescopes, Calibration, Spectral resolution, Telescopes, Device simulation, Spectrographs

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Proceedings Article | 9 September 2019 Presentation

Presentation

Spectral and radiometric calibration of WFIRST slitless spectrometer (grism) (Conference Presentation)

Qian Gong, Matthew Bergkoetter, Joshua Berrier, John Chambers, Margaret Dominguez, Wesley Fincher, John Hagopian, Catherine Marx

Proceedings Volume 11115, 1111503 (2019) https://doi.org/10.1117/12.2530712

KEYWORDS: Calibration, Spectral calibration, Spectroscopy, Data modeling, Optical design, Light sources, Sensors, Diffraction, Spectral resolution, Point spread functions

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Proceedings Article | 9 September 2019 Presentation + Paper

Presentation + Paper

Phase-retrieval-based wavefront metrology for high-contrast coronography: 2. Reconstructions through a shaped pupil apodizer

Gregory Brady, Peter Petrone, Iva Laginja, Keira Brooks, Manxuan (Rebecca) Zhang, Mamadou N'Diaye, Christopher Moriarty, John Hagopian, Rémi Soummer

Proceedings Volume 11117, 1111712 (2019) https://doi.org/10.1117/12.2530482

KEYWORDS: Wavefronts, Wavefront metrology, Phase retrieval, Coronagraphy, Manufacturing, Exoplanets, Binary data, Imaging systems, Phase measurement, Deformable mirrors

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Proceedings Article | 9 September 2019 Presentation

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 | 30 August 2019 Presentation + Paper

Presentation + Paper

Global Ecosystem Dynamics Investigation (GEDI) instrument alignment and test

Bente Eegholm, Shane Wake, Zachary Denny, Pete Dogoda, Demetrios Poulios, Barry Coyle, Pete Mulé, John Hagopian, Patrick Thompson, Luis Ramos-Izquierdo, Bryan Blair

Proceedings Volume 11103, 1110308 (2019) https://doi.org/10.1117/12.2532471

KEYWORDS: LIDAR, Optical metrology, Transmitters, Optical fibers, Mirrors, Optical benches, Telescopes, Collimators, Optical alignment, Receivers, Beam expanders

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Proceedings Article | 30 August 2019 Presentation + Paper

Presentation + Paper

Alignment and test of the Wide Field Infrared Survey Telescope (WFIRST) Engineering Design Unit (EDU) grism

John Hagopian, Josh Berrier, John Chambers, David Content, Margaret Dominguez, Qian Gong, Jason Krom, Catherine Marx, Joseph McMann, Bert Pasquale, Laurie Seide, Arthur Whipple, Patrick Williams

Proceedings Volume 11103, 1110306 (2019) https://doi.org/10.1117/12.2530697

KEYWORDS: Wavefronts, Optical alignment, LIDAR, Chemical elements, Telescopes, Computer generated holography, Infrared telescopes, Interferometers, Optical spheres, Optical instrument design

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Proceedings Article | 13 May 2019 Paper

Paper

Future planetary instrument capabilities made possible by micro- and nanotechnology

Stephanie Getty, Lucy Lim, Andrej Grubisic, Adrian Southard, Jerome Ferrance, Manuel Balvin, Xiang Li, Timothy Cornish, Jamie Elsila, Larry Hess, Carl Kotecki, John Hagopian, William Brinckerhoff

Proceedings Volume 10982, 109820F (2019) https://doi.org/10.1117/12.2519455

KEYWORDS: Liquids, X-rays, Solar system, Mass spectrometry, Spectroscopy, Carbon nanotubes, Chemical elements

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Proceedings Article | 17 September 2018 Presentation + Paper

Presentation + Paper

Optical design and predicted performance of the WFIRST phase-b imaging optics assembly and wide field instrument

Bert Pasquale, Thomas Casey, Catherine Marx, Guangjun Gao, Nerses Armani, David Content, John Hagopian, Alden Jurling, Clifton Jackson, Alice Liu, Art Whipple, Jacob Murray

Proceedings Volume 10745, 107450K (2018) https://doi.org/10.1117/12.2325859

KEYWORDS: Mirrors, Observatories, Optical design, Telescopes, Space operations, Staring arrays, Coronagraphy, Optical alignment, Finite element methods

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Proceedings Article | 21 August 2018 Presentation + Paper

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

Read Abstract +

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 | 14 July 2018

Infrared computer-generated holograms: design and application for the WFIRST grism using wavelength-tuning interferometry

Margaret Z. Dominguez, Catherine T. Marx, Qian Gong, John G. Hagopian, Ulf Griesmann, James H. Burge, Dae Wook Kim

OE, Vol. 57, Issue 07, 074105, (July 2018) https://doi.org/10.1117/12.10.1117/1.OE.57.7.074105

KEYWORDS: Computer generated holography, Infrared radiation, Interferometers, Interferometry, Wavefronts, Optical design, Phase shifts, Infrared telescopes, Diffraction, Prototyping

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Proceedings Article | 10 July 2018 Presentation

Presentation

The wide field infrared survey telescope (WFIRST) observatory: design formulation (phase-A) overview (Conference Presentation)

Thomas Casey, Nerses Armani, Wes Alexander, Lisa Bartusek, Carl Blaurock, David Braun, Alexander Carra, David Content, Yves Conturie, Christine Cottingham, Richard Demers, Michael Dipirro, Robert Effinger, Robert Egerman, Frank Forkl, Guangjun Gao, John Gygax, John Hagopian, Timothy Hahm, John Hawk, Gurnie Hobbs, Clifton Jackson, Alden Jurling, Brian Kern, Jeffrey Kruk, Xiaoyi Li, Kuo-chia Liu, Catherine Marx, Marzouk Marzouk, Carson McDonald, Seke Godo, Mark Melton, James Mondello, M. Charley Noecker, Bert Pasquale, Hume Peabody, Ilya Poberezhskiy, Cory Powell, Giulio Rosanova, John Ruffa, Jeffrey Smith, Hong Tang, Christopher Tolman, Arthur Whipple, Timothy Wilson, Melissa Vess, Perry Voyer

Proceedings Volume 10698, 106982C (2018) https://doi.org/10.1117/12.2313748

KEYWORDS: Infrared telescopes, Space telescopes, Observatories, Telescopes, Infrared radiation, Optical instrument design, Infrared imaging, Exoplanets, Imaging spectroscopy, Coronagraphy

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Proceedings Article | 29 August 2017 Presentation + Paper

Presentation + Paper

Scattered light characterization of FORTIS

Stephan McCandliss, Anna Carter, Keith Redwine, Stephane Teste, Russell Pelton, John Hagopian, Alexander Kutyrev, Mary Li, S. Harvey Moseley

Proceedings Volume 10397, 1039718 (2017) https://doi.org/10.1117/12.2274282

KEYWORDS: Imaging spectroscopy, Light scattering, Collimators, 3D modeling, Carbon nanotubes, Carbon, Foam, Device simulation, Space telescopes, Telescopes

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Proceedings Article | 22 August 2017 Presentation + Paper

Presentation + Paper

Ground to on-orbit alignment study of the WFIRST wide-field channel and resulting changes in the telescope architecture

John Hagopian, Nerses Armani, Lisa Bartusek, Tom Casey, Dave Content, Yves Conturie, Guangjun Gao, Alden Jurling, Cathy Marx, Joe Marzouk, Bert Pasquale, J. Scott Smith, Hong Tang, Arthur Whipple

Proceedings Volume 10377, 103770E (2017) https://doi.org/10.1117/12.2280333

KEYWORDS: Space telescopes, Telescopes, Mirrors, Infrared telescopes, Space operations, Optical telescopes, Coronagraphy, Monte Carlo methods, Infrared astronomy, Infrared radiation

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Proceedings Article | 20 October 2016 Presentation + Paper

Presentation + Paper

A toolbox of metrology-based techniques for optical system alignment

Phillip Coulter, Raymond Ohl, Peter Blake, Brent Bos, Victor Chambers, William Eichhorn, Jeffrey Gum, Theodore Hadjimichael, John Hagopian, Joseph Hayden, Samuel Hetherington, David Kubalak, Kyle Mclean, Joseph McMann, Kevin Redman, Henry Sampler, Greg Wenzel, Jerrod Young

Proceedings Volume 9951, 995108 (2016) https://doi.org/10.1117/12.2239070

KEYWORDS: Optical alignment, Metrology, Optical components, James Webb Space Telescope, Mirrors, Telescopes, Lawrencium, Sensors, Spherical lenses, Optical benches

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Proceedings Article | 19 September 2016 Presentation + Paper

Presentation + Paper

Advanced topographic laser altimeter system (ATLAS) receiver telescope assembly (RTA) and transmitter alignment and test

John Hagopian, Matthew Bolcar, John Chambers, Allen Crane, Bente Eegholm, Tyler Evans, Samuel Hetherington, Eric Mentzell, Patrick Thompson, Luis Ramos-Izquierdo, David Vaughnn

Proceedings Volume 9972, 997207 (2016) https://doi.org/10.1117/12.2240241

KEYWORDS: Space telescopes, Telescopes, Optical fibers, Receivers, Transmitters, Diffractive optical elements, Collimators, Wavefronts, Mirrors, Interferometers

Read Abstract +

The sole instrument on NASA’s ICESat-2 spacecraft shown in Figure 1 will be the Advanced Topographic Laser Altimeter System (ATLAS)¹. The ATLAS is a Light Detection and Ranging (LIDAR) instrument; it measures the time of flight of the six transmitted laser beams to the Earth and back to determine altitude for geospatial mapping of global ice. The ATLAS laser beam is split into 6 main beams by a Diffractive Optical Element (DOE) that are reflected off of the earth and imaged by an 800 mm diameter Receiver Telescope Assembly (RTA). The RTA is composed of a 2-mirror telescope and Aft Optics Assembly (AOA) that collects and focuses the light from the 6 probe beams into 6 science fibers. Each fiber optic has a field of view on the earth that subtends 83 micro Radians. The light collected by each fiber is detected by a photomultiplier and timing related to a master clock to determine time of flight and therefore distance. The collection of the light from the 6 laser spots projected to the ground allows for dense cross track sampling to provide for slope measurements of ice fields. NASA LIDAR instruments typically utilize telescopes that are not diffraction limited since they function as a light collector rather than imaging function. The more challenging requirements of the ATLAS instrument require better performance of the telescope at the ¼ wave level to provide for improved sampling and signal to noise. NASA Goddard Space Flight Center (GSFC) contracted the build of the telescope to General Dynamics (GD). GD fabricated and tested the flight and flight spare telescope and then integrated the government supplied AOA for testing of the RTA before and after vibration qualification. The RTA was then delivered to GSFC for independent verification and testing over expected thermal vacuum conditions. The testing at GSFC included a measurement of the RTA wavefront error and encircled energy in several orientations to determine the expected zero gravity figure, encircled energy, back focal length and plate scale. In addition, the science fibers had to be aligned to within 10 micro Radians of the projected laser spots to provide adequate margin for operations on-orbit. This paper summarizes the independent testing and alignment of the fibers performed at the GSFC.

Proceedings Article | 9 August 2016 Paper

Paper

Wide-Field InfraRed Survey Telescope (WFIRST) slitless spectrometer: design, prototype, and results

Qian Gong, David Content, Margaret Dominguez, Thomas Emmett, Ulf Griesmann, John Hagopian, Jeffrey Kruk, Catherine Marx, Bert Pasquale, Thomas Wallace, Arthur Whipple

Proceedings Volume 9904, 990412 (2016) https://doi.org/10.1117/12.2231665

KEYWORDS: Prototyping, Spectroscopy, Optical design, Chemical elements, Interferometers, Computer generated holography, Wavefronts, Diffraction, Diffraction gratings, Collimation

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Proceedings Article | 11 October 2012 Paper

Paper

light weight silicon mirrors for space instrumentation

Vincent Bly, Peter Hill, John Hagopian, Carl Strojny, Timothy Miller

Proceedings Volume 8486, 84860P (2012) https://doi.org/10.1117/12.929818

KEYWORDS: Mirrors, Silicon, Crystals, Space mirrors, Lightweight mirrors, Polishing, Aerospace engineering, Heat treatments, Distortion, Silicon carbide

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Proceedings Article | 21 September 2012 Paper

Paper

Spherical primary optical telescope (SPOT) segments

Christopher Hall, John Hagopian, Michael DeMarco

Proceedings Volume 8442, 844222 (2012) https://doi.org/10.1117/12.926479

KEYWORDS: Mirrors, Magnetorheological finishing, Polishing, Magnetism, Spherical lenses, Optical telescopes, Space telescopes, Composites, Surface finishing, Actuators

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Proceedings Article | 29 September 2011 Paper

Paper

Hemispherical reflectance and emittance properties of carbon nanotubes coatings at infrared wavelengths

Manuel Quijada, John Hagopian, Stephanie Getty, Raymond Kinzer, Edward Wollack

Proceedings Volume 8150, 815002 (2011) https://doi.org/10.1117/12.894601

KEYWORDS: Reflectivity, Silicon, Carbon nanotubes, Infrared radiation, Optical spheres, Calibration, Sensors, Integrating spheres, Temperature metrology, Absorption

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Proceedings Article | 21 September 2011 Paper

Paper

Fabrication and test of an optical magnetic mirror

John Hagopian, Patrick Roman, Shahram Shiri, Edward Wollack, Madhumita Roy

Proceedings Volume 8096, 80963W (2011) https://doi.org/10.1117/12.903925

KEYWORDS: Mirrors, Magnetism, Diffraction, Dielectric polarization, Control systems, Semiconducting wafers, Dielectrics, Phase shifts, Nanostructures, Nanowires

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Proceedings Article | 4 November 2010 Paper

Paper

Initial studies of the bidirectional reflectance distribution function of carbon nanotube structures for stray light control applications

James Butler, Georgi Georgiev, June Tveekrem, Manuel Quijada, Stephanie Getty, John Hagopian

Proceedings Volume 7862, 78620D (2010) https://doi.org/10.1117/12.869569

KEYWORDS: Bidirectional reflectance transmission function, Reflectivity, Silicon, Carbon nanotubes, Stray light, Light scattering, Titanium, Optical testing, Stray light control, Diffusers

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Proceedings Article | 9 September 2010 Paper

Paper

Optical design for the Composite InfraRed Spectrometer Lite (CIRS-Lite)

Bert Pasquale, John Brasunas, John Hagopian, Qian Gong, William Mamakos, Melissa Edgerton, Vincent Bly

Proceedings Volume 7652, 76520Q (2010) https://doi.org/10.1117/12.879044

KEYWORDS: Mirrors, Telescopes, Interferometers, Infrared spectroscopy, Optical design, Solar concentrators, Beam splitters, Infrared radiation, Relays, Vignetting

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Proceedings Article | 31 August 2010 Paper

Paper

Multiwalled carbon nanotubes for stray light suppression in space flight instruments

John Hagopian, Stephanie Getty, Manuel Quijada, June Tveekrem, Ron Shiri, Patrick Roman, James Butler, Georgi Georgiev, Jeff Livas, Cleophus Hunt, Alejandro Maldonado, Saikat Talapatra, Xianfeng Zhang, Stergios Papadakis, Andrew Monica, David Deglau

Proceedings Volume 7761, 77610F (2010) https://doi.org/10.1117/12.864386

KEYWORDS: Stray light, Mirrors, Reflectivity, Carbon nanotubes, Silicon, Bidirectional reflectance transmission function, Aerospace engineering, Nanoimprint lithography, Stray light control, Light scattering

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Observations of the Earth are extremely challenging; its large angular extent floods scientific instruments with high flux within and adjacent to the desired field of view. This bright light diffracts from instrument structures, rattles around and invariably contaminates measurements. Astrophysical observations also are impacted by stray light that obscures very dim objects and degrades signal to noise in spectroscopic measurements. Stray light is controlled by utilizing low reflectance structural surface treatments and by using baffles and stops to limit this background noise. In 2007 GSFC researchers discovered that Multiwalled Carbon Nanotubes (MWCNTs) are exceptionally good absorbers, with potential to provide order-of-magnitude improvement over current surface treatments and a resulting factor of 10,000 reduction in stray light when applied to an entire optical train. Development of this technology will provide numerous benefits including: a.) simplification of instrument stray light controls to achieve equivalent performance, b.) increasing observational efficiencies by recovering currently unusable scenes in high contrast regions, and c.) enabling low-noise observations that are beyond current capabilities. Our objective was to develop and apply MWCNTs to instrument components to realize these benefits. We have addressed the technical challenges to advance the technology by tuning the MWCNT geometry using a variety of methods to provide a factor of 10 improvement over current surface treatments used in space flight hardware. Techniques are being developed to apply the optimized geometry to typical instrument components such as spiders, baffles and tubes. Application of the nanostructures to alternate materials (or by contact transfer) is also being investigated. In addition, candidate geometries have been tested and optimized for robustness to survive integration, testing, launch and operations associated with space flight hardware. The benefits of this technology extend to space science where observations of extremely dim objects require suppression of stray light.

Proceedings Article | 23 July 2010 Paper

Paper

Post-flight reflectance of COSTAR and WF/PC 2 pickoff mirrors upon their return from space

Manuel Quijada, Ross Henry, Timothy Madison, Rene Boucarut, John Hagopian

Proceedings Volume 7739, 77392J (2010) https://doi.org/10.1117/12.858072

KEYWORDS: Mirrors, Reflectivity, Coating, Optical fiber cables, Ultraviolet radiation, Space telescopes, Space mirrors, Contamination, Cameras, Hubble Space Telescope

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Proceedings Article | 2 September 2008 Paper

Paper

Optical metrology and alignment of the James Webb Space Telescope Integrated Science Instrument Module

Joseph Connelly, Brent Bos, Pamela Davila, William Eichhorn, Bradley Frey, John Hagopian, Jason Hylan, James Marsh, Douglas McGuffey, Joseph McMann, Maria Nowak, Raymond Ohl, Kevin Redman, Derek Sabatke, Henry Sampler, Joseph Stock, Joseph Sullivan, Gregory Wenzel, Geraldine Wright, Philip Young

Proceedings Volume 7068, 70680F (2008) https://doi.org/10.1117/12.798778

KEYWORDS: Interfaces, Optical alignment, James Webb Space Telescope, Metrology, Cryogenics, Mirrors, Photogrammetry, Optical components, Cameras, Optical tracking

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Proceedings Article | 12 July 2008 Paper

Paper

Cryogenic pupil alignment test architecture for the James Webb Space Telescope integrated science instrument module

Brent Bos, David Kubalak, Scott Antonille, Raymond Ohl, John Hagopian, Pamela Davila, Joseph Sullivan, Michael Sánchez, Derek Sabatke, Robert Woodruff, Maurice te Plate, Clinton Evans, Victor Isbrucker, Stephen Somerstein, Martyn Wells, Samuel Ronayette

Proceedings Volume 7010, 70103C (2008) https://doi.org/10.1117/12.789808

KEYWORDS: James Webb Space Telescope, Mirrors, Sensors, Observatories, Optical components, Reflectivity, Cryogenics, Stray light, Beam splitters, Infrared telescopes

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Proceedings Article | 17 September 2007 Paper

Paper

Optical alignment of the JWST ISIM to the OTE simulator (OSIM): current concept and design studies

Bradley Frey, Pamela Davila, John Hagopian, James Marsh, Raymond Ohl, Mark Wilson, Philip Young

Proceedings Volume 6692, 66920R (2007) https://doi.org/10.1117/12.736050

KEYWORDS: James Webb Space Telescope, Optical alignment, Cryogenics, Optical cryogenics, Space telescopes, Aerospace engineering, Space operations, Optical telescopes, Optical components, Device simulation

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Proceedings Article | 22 June 2006 Paper

Paper

Developing a NASA strategy for the verification of large space telescope observatories

Julie Crooke, Johanna Gunderson, John Hagopian, Marie Levine

Proceedings Volume 6271, 627108 (2006) https://doi.org/10.1117/12.670209

KEYWORDS: James Webb Space Telescope, Space telescopes, Observatories, Telescopes, Mirrors, Astronomy, Nanoimprint lithography, Modeling and simulation, Performance modeling, Space operations

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Proceedings Article | 22 June 2006 Paper

Paper

Optical verification of the James Webb Space Telescope

Brian McComas, Rich Rifelli, Allison Barto, Adam Contos, Tony Whitman, Conrad Wells, John Hagopian

Proceedings Volume 6271, 62710A (2006) https://doi.org/10.1117/12.672448

KEYWORDS: Observatories, James Webb Space Telescope, Image quality, Mirrors, Cryogenics, Space telescopes, Data modeling, Telescopes, Optical components, Optical testing

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Proceedings Article | 13 June 2006 Paper

Paper

Focus determination for the James Webb Space Telescope science instruments: a survey of methods

Pamela Davila, Matthew Bolcar, Brent Bos, Bruce Dean, John Hagopian, Joseph Howard, Blair Unger, Mark Wilson

Proceedings Volume 6265, 626512 (2006) https://doi.org/10.1117/12.673383

KEYWORDS: James Webb Space Telescope, Point spread functions, Space telescopes, Telescopes, Sensors, Code v, Linear filtering, Mirrors, Cameras, Wavefronts

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Proceedings Article | 10 June 2006 Paper

Paper

New approach to cryogenic optical testing the James Webb Space Telescope

Lee Feinberg, John Hagopian, Charles Diaz

Proceedings Volume 6265, 62650P (2006) https://doi.org/10.1117/12.660396

KEYWORDS: James Webb Space Telescope, Cryogenics, Optical testing, Telescopes, Mirrors, Space telescopes, Interferometers, Picture Archiving and Communication System, Metrology, Optical testing equipment

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Proceedings Article | 12 December 2003 Paper

Paper

Lightweight mirrors from single-crystal silicon

Vincent Bly, David Content, John Hagopian, Linette Kolos, David Moore

Proceedings Volume 5179, (2003) https://doi.org/10.1117/12.511569

KEYWORDS: Mirrors, Silicon, Surface finishing, Lightweight mirrors, Silicon carbide, Polishing, Crystals, Ultrasonics, Etching, Space mirrors

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Proceedings Article | 15 October 2003 Paper

Paper

Alignment of the grating wheel mechanism for a ground-based cryogenic near-infrared astronomy instrument

Sharon Gutkowski, Raymond Ohl, Jason Hylan, John Hagopian, Stephen Kraft, J. Mentzell, Joseph Connelly, Joseph Schepis, Leroy Sparr, Matthew Greenhouse, John MacKenty

Proceedings Volume 5172, (2003) https://doi.org/10.1117/12.503506

KEYWORDS: Optical alignment, Mirrors, Tolerancing, Cryogenics, Liquid crystals, Telescopes, Computer aided design, Metrology, James Webb Space Telescope

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Proceedings Article | 7 March 2003 Paper

Paper

Design and fabrication of diamond-machined aspheric mirrors for ground-based near-IR astronomy

Raymond Ohl, Werner Preuss, Alex Sohn, Shelly Conkey, Ken Garrard, John Hagopian, Joseph Howard, Jason Hylan, Sandra Irish, John Mentzell, Mechthild Schroeder, Leroy Sparr, Robert Winsor, Said Wahid Zewari, Matthew Greenhouse, John MacKenty

Proceedings Volume 4841, (2003) https://doi.org/10.1117/12.458967

KEYWORDS: Mirrors, Aluminum, Optical alignment, Spindles, Off axis mirrors, Tolerancing, Diamond, Space telescopes, Optical fabrication, Single point diamond turning

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Proceedings Article | 7 March 2003 Paper

Paper

Imaging performance and modeling of the infrared multi-object spectrometer focal reducer

Joseph Connelly, Raymond Ohl, Timo Saha, Theo Hadjimichael, John Mentzell, Ronald Mink, Jason Hylan, Leroy Sparr, John Chambers, John Hagopian, Matthew Greenhouse, Robert Winsor, John MacKenty

Proceedings Volume 4841, (2003) https://doi.org/10.1117/12.458974

KEYWORDS: Mirrors, Telescopes, Space telescopes, Wavefronts, Infrared spectroscopy, Optical alignment, Spectroscopy, Sensors, Light scattering, Tolerancing

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Proceedings Article | 25 November 2002 Paper

Paper

Comparison of stress-relief procedures for cryogenic aluminum mirrors

Raymond Ohl, Michael Barthelmy, Said Wahid Zewari, Ronald Toland, Joseph McMann, David Puckett, John Hagopian, Jason Hylan, John Mentzell, Ronald Mink, Leroy Sparr, Matthew Greenhouse, John MacKenty

Proceedings Volume 4822, (2002) https://doi.org/10.1117/12.451762

KEYWORDS: Mirrors, Aluminum, Heat treatments, Spherical lenses, Cryogenics, Temperature metrology, Single point diamond turning, Camera shutters, Error analysis, Space telescopes

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Proceedings Article | 28 July 2000 Paper

Paper

NGST OTA optical metrology instrumentation and conceptual approaches

Ritva Keski-Kuha, Pierre Bely, Richard Burg, James Burge, Pamela Davila, Joseph Geary, John Hagopian, David Jacobson, Andrew Lowman, Steven Macenka, John Mangus, Charles Perrygo, David Redding, Babak Saif, W. Scott Smith, James Wyant

Proceedings Volume 4013, (2000) https://doi.org/10.1117/12.394050

KEYWORDS: Mirrors, Cryogenics, Interferometers, Wavefronts, Interferometry, Calibration, Computer generated holography, Optical testing, Phase shifts, Telescopes

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Proceedings Article | 17 September 1998 Paper

Paper

Shear/defocus sensitivity of the mid-infrared channel (MIR) of the composite infrared spectometer (CIRS) for the Cassini mission to Saturn

John Hagopian, Patricia Losch, Julie Crooke, Brent Mott, Anthony Martino

Proceedings Volume 3435, (1998) https://doi.org/10.1117/12.323744

KEYWORDS: Interferometers, Germanium, Calibration, Beam splitters, Wavefronts, Cryogenics, Mid-IR, Infrared spectroscopy, Black bodies, Far infrared

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Proceedings Article | 17 September 1998 Paper

Paper

Alignment and polarization sensitivity study for the Cassini composite infrared spectrometer (CIRS) far-infrared (FIR) interferometer

Julie Crooke, John Hagopian

Proceedings Volume 3435, (1998) https://doi.org/10.1117/12.323743

KEYWORDS: Interferometers, Polarization, Beam splitters, Polarizers, Sensors, Infrared spectroscopy, Optical alignment, Spectroscopy, Calibration, Far infrared

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Proceedings Article | 17 September 1998 Paper

Paper

Effects of shear, defocus, and wavefront error on the theoretical performance of the composite infrared spectrometer for Cassini

Anthony Martino, John Hagopian

Proceedings Volume 3435, (1998) https://doi.org/10.1117/12.323745

KEYWORDS: Sensors, Wavefronts, Modulation, Interferometers, Beam splitters, Infrared spectroscopy, Spectroscopy, Signal detection, Reflectivity, Composites

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Proceedings Article | 17 September 1998 Paper

Paper

Acoustic amplification in the far-infrared focal plane assembly of the composite infrared spectrometer (CIRS) for the Cassini mission to Saturn

John Hagopian, Julie Crooke

Proceedings Volume 3435, (1998) https://doi.org/10.1117/12.323738

KEYWORDS: Sensors, Acoustics, Mirrors, Infrared spectroscopy, Gold, Resistance, Saturn, Interferometers, Spectroscopy, Far infrared

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Proceedings Article | 17 September 1998 Paper

Paper

Cryogenic optical performance of the Cassini composite infrared spectrometer (CIRS) flight telescope

Patricia Losch, James Lyons, John Hagopian

Proceedings Volume 3435, (1998) https://doi.org/10.1117/12.323742

KEYWORDS: Telescopes, Mirrors, Space telescopes, Beryllium, Cryogenics, Collimation, Infrared spectroscopy, Infrared telescopes, Reticles, Phase modulation

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Proceedings Article | 17 September 1998 Paper

Paper

Throughput of the composite infrared spectrometer (CIRS) mid-infrared (MIR) channel for the Cassini mission to Saturn

John Hagopian, Patricia Losch, Kenneth Stewart, Donald Jennings, Anthony Martino

Proceedings Volume 3435, (1998) https://doi.org/10.1117/12.323737

KEYWORDS: Modulation, Beam splitters, Interferometers, Reflectivity, Infrared spectroscopy, Mid-IR, Reflection, Spectroscopy, Mirrors, Far infrared

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Proceedings Article | 14 October 1996 Paper

Paper

High-stability adjustable cryogenic-compatible beam-splitter mounts for the Composite Infrared Spectrometer (CIRS) for the Cassini mission to Saturn

John Hagopian, Patricia Hayes, Julie Crooke, James Lyons, Armando Morrell, Thomas French, Michael Hersh, Chris Lashley, Stephen Schmidt

Proceedings Volume 2814, (1996) https://doi.org/10.1117/12.254150

KEYWORDS: Beam splitters, Cryogenics, Interferometers, Infrared spectroscopy, Spectroscopy, Interferometry, Saturn, Optical alignment, Composites, Far infrared

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Proceedings Article | 14 October 1996 Paper

Paper

Cryogenic Interferometric Alignment (CIA) of the Composite Infrared Spectrometer (CIRS) engineering unit for the Cassini mission to Saturn

John Hagopian

Proceedings Volume 2814, (1996) https://doi.org/10.1117/12.254149

KEYWORDS: Beam splitters, Cryogenics, Interferometry, Interferometers, Infrared spectroscopy, Distortion, Spectroscopy, Saturn, Polarization, Far infrared

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Proceedings Article | 14 October 1996 Paper

Paper

Cryogenic Optical Alignment Stability Test (COAST) of the Composite Infrared Spectrometer (CIRS) engineering unit for the Cassini mission to Saturn

John Hagopian

Proceedings Volume 2814, (1996) https://doi.org/10.1117/12.254148

KEYWORDS: Beam splitters, Cryogenics, Interferometers, Distortion, Optical alignment, Infrared spectroscopy, Medium wave, Mirrors, Camera shutters, Far infrared

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Proceedings Article | 14 October 1996 Paper

Paper

Alignment verification by wavefront testing of the composite infrared spectrometer

Patricia Hayes, James Lyons, John Hagopian

Proceedings Volume 2814, (1996) https://doi.org/10.1117/12.254151

KEYWORDS: Mirrors, Wavefronts, Optical alignment, Telescopes, Interferometers, Infrared spectroscopy, Polarizers, Spectroscopy, Electroactive polymers, Far infrared

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Proceedings Article | 14 October 1996 Paper

Paper

Flight qualification of the Cassini Composite InfraRed Spectrometer (CIRS) far-infrared (FIR) polarizing beam-splitter substrate: mylar chosen over polypropylene

Julie Crooke, John Hagopian, Kenneth Stewart, Scott Bradley, David Robinson

Proceedings Volume 2814, (1996) https://doi.org/10.1117/12.254135

KEYWORDS: Beam splitters, Reflectivity, Cryogenics, Polarizers, Transmittance, Acoustics, Interferometers, Polarization, Humidity, Far infrared

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Proceedings Article | 14 October 1996 Paper

Paper

Optomechanical alignment of the Composite Infrared Spectrometer (CIRS) for the Cassini mission to Saturn

John Hagopian, Patricia Hayes, Julie Crooke, James Lyons

Proceedings Volume 2814, (1996) https://doi.org/10.1117/12.254147

KEYWORDS: Mirrors, Optical alignment, Tolerancing, Interferometers, Infrared spectroscopy, Telescopes, Relays, Beam splitters, Medium wave, Far infrared

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Proceedings Article | 14 October 1996 Paper

Paper

Alignment and cryogenic testing of the Cassini Composite InfraRed Spectrometer (CIRS) far-infrared (FIR) focal plane

Julie Crooke, John Hagopian

Proceedings Volume 2814, (1996) https://doi.org/10.1117/12.254152

KEYWORDS: Sensors, Mirrors, Collimation, Cryogenics, Infrared radiation, Black bodies, Signal detection, Infrared spectroscopy, Spectroscopy, Far infrared

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Proceedings Article | 7 October 1996 Paper

Paper

Cassini infrared Fourier spectroscopic investigation

Virgil Kunde, Peter Ade, Richard Barney, D. Bergman, Jean-Francois Bonnal, R. Borelli, David Boyd, John Brasunas, Gregory Brown, Simon Calcutt, F. Carroll, R. Courtin, Jacky Cretolle, Julie Crooke, Martin Davis, S. Edberg, Rainer Fettig, M. Flasar, David Glenar, S. Graham, John Hagopian, Claef Hakun, Patricia Hayes, L. Herath, Linda Spilker, Donald Jennings, Gabriel Karpati, C. Kellebenz, Brook Lakew, J. Lindsay, J. Lohr, James Lyons, Robert Martineau, Anthony Martino, Mack Matsumura, J. McCloskey, T. Melak, Guy Michel, Armando Morrell, C. Mosier, LaTunia Pack, M. Plants, D. Robinson, Louis Rodriguez, Paul Romani, Bill Schaefer, Stephen Schmidt, Carlos Trujillo, Tim Vellacott, K. Wagner, D. Yun

Proceedings Volume 2803, (1996) https://doi.org/10.1117/12.253416

KEYWORDS: Interferometers, Sensors, Mirrors, Telescopes, Infrared spectroscopy, Infrared radiation, Mid-IR, Beam splitters, Mercury cadmium telluride, Space telescopes

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Proceedings Article | 14 July 1995 Paper

Paper

High-reflectance coatings and materials for the extreme ultraviolet

Ritva Keski-Kuha, John Osantowski, Gerry Blumenstock, Jeffrey Gum, Charles Fleetwood, Douglas Leviton, Timo Saha, John Hagopian, June Tveekrem, Geraldine Wright

Proceedings Volume 2428, (1995) https://doi.org/10.1117/12.213712

KEYWORDS: Reflectivity, Mirrors, Silicon carbide, Optical coatings, Extreme ultraviolet, Ion beams, Polishing, Multilayers, Chemical vapor deposition, Contamination

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Proceedings Article | 19 October 1994 Paper

Paper

Qualification of CO2 jet spray cleaning for use on magnesium-fluoride-protected aluminum coatings for the corrective optics space telescope axial replacement (COSTAR)

John Hagopian, Charles Fleetwood, Ritva Keski-Kuha, Douglas Leviton, Geraldine Wright, Charles Bowers

Proceedings Volume 2261, (1994) https://doi.org/10.1117/12.190154

KEYWORDS: Mirrors, Contamination, Optical coatings, Reflectivity, Carbon dioxide, Optical testing, Surface roughness, Particles, UV optics, Ultraviolet radiation

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Proceedings Article | 1 November 1990 Paper

Paper

Calibration of optical detectors using discrete Fourier transform techniques

John Hagopian, William Eichhorn

Proceedings Volume 1340, (1990) https://doi.org/10.1117/12.23065

KEYWORDS: Sensors, Calibration, Fourier transforms, Modulation, Bolometers, Signal detection, Optical cryogenics, Computing systems, Optical calibration, Phase shift keying

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Showing 5 of 64 publications

Conference Committee Involvement (1)

Cryogenic Optical Systems and Instruments XI

1 August 2005 | San Diego, California, United States

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