Dr. John Z. Lou Profile

Dr. John Z. Lou

Technical Staff at Jet Propulsion Lab

SPIE Involvement:

Author

Publications (14)

Proceedings Article | 5 October 2023 Presentation + Paper

Integrated active control of coronagraph and telescope for high contrast imaging

David Redding, Erkin Sidick, John Lou, Brandon Dube, Scott Basinger

Proceedings Volume 12680, 126801M (2023) https://doi.org/10.1117/12.2678150

KEYWORDS: Coronagraphy, Telescopes, Sensors, Electric fields, Wavefront sensors, Equipment, Stars, Metrology, Laser metrology, Wavefront errors

Read Abstract +

Proceedings Article | 27 August 2022 Presentation + Paper

Line-of-sight and wavefront error dynamic stability during coronagraphic imaging for a 6.7-meter inscribed diameter UVOIR segmented telescope with non-contact pointing and vibration isolation

Kiarash Tajdaran, Larry Dewell, Michael Jacoby, Alison Nordt, John Lou

Proceedings Volume 12180, 121802L (2022) https://doi.org/10.1117/12.2630343

KEYWORDS: Control systems, Space operations, Actuators, Interfaces, Sensors, Observatories, Performance modeling, Wavefronts, Coronagraphy, Telescopes

Read Abstract +

The Ultraviolet/Optical/Infrared (UVOIR) flagship astrophysics architectures proposed by the Astro2020 Decadal Survey fundamentally challenge the current test-like-you-fly approach to space systems, because of their physical scale, multiple stages of on-orbit deployment, and extremely stringent optical performance requirements unique to visible-light coronagraphy. These limitations elevate the importance of integrated control, structural dynamics, and optical modeling, particularly in early system architecture studies. A unique non-contact observatory control architecture called Disturbance Free Payload (DFP) for next-generation large astrophysics observatories involves physically isolating the segmented telescope structure from the supporting spacecraft by means of a non-contact interface. In this control architecture, rigidbody telescope pointing is achieved by actuating the payload with non-contact voice coil actuators and maintaining positive interface gaps using spacecraft inertial actuators and interface non-contact sensors. This architecture presents distinct advantages over current state-of-the-art spacecraft vibration isolation approaches, particularly for large flexible spacecraft, but also introduces unique disturbance and coupling mechanisms that must be analyzed. In this paper, development of an integrated model is described, consisting of a 6.7-meter inscribed segmented optical system, and an unobscured telescope with 55 primary mirror segments. The paper starts with an overview of the models that directly predict time-domain lineof-sight and wavefront error dynamic stability (optics, dynamics, control system, error sources). Next, key dynamic stability performance metrics for coronagraph contrast performance are described and a systematic methodology for realizing an accurate but computationally feasible truncated modal model is presented. Finally, an exemplar point design that is compliant to 10-picometer RMS wavefront error is developed, and the necessary component errors to achieve this performance are presented.

Proceedings Article | 6 July 2018 Paper

LUVOIR primary mirror segment alignment control with joint laser metrology and segment edge sensing

John Lou, David Redding, Joel Nissen, Chris Shelton

Proceedings Volume 10698, 1069840 (2018) https://doi.org/10.1117/12.2311495

KEYWORDS: Wavefronts, Sensors, Metrology, Wavefront sensors, Mirrors, Error analysis, Laser metrology, Image segmentation, Control systems, Monte Carlo methods

Read Abstract +

Proceedings Article | 27 September 2012 Paper

The CCAT 25m diameter submillimeter-wave telescope

David Woody, Steve Padin, Eric Chauvin, Bruno Clavel, German Cortes, Andy Kissil, John Lou, Paul Rasmussen, David Redding, Jeff Zolkower

Proceedings Volume 8444, 84442M (2012) https://doi.org/10.1117/12.925229

KEYWORDS: Telescopes, Wavefronts, Sensors, Control systems, Actuators, Distortion, Cameras, Reflectors, Image segmentation, Mirrors

Read Abstract +

Proceedings Article | 10 November 2011 Paper

Model-based wavefront control for CCAT

David Redding, John Lou, Andy Kissil, Matt Bradford, Steve Padin, David Woody

Proceedings Volume 8336, 83360Q (2011) https://doi.org/10.1117/12.916694

KEYWORDS: Sensors, Telescopes, Error analysis, Wavefronts, Phase modulation, Actuators, Image segmentation, Mirrors, Motion measurement, Control systems

Read Abstract +

Proceedings Article | 11 August 2010 Paper

Modeling a large submillimeter-wave observatory

John Lou, Andy Kissil, Dave Redding, Matt Bradford, Steve Padin, David Woody

Proceedings Volume 7733, 773326 (2010) https://doi.org/10.1117/12.856493

KEYWORDS: Wavefronts, Image segmentation, Sensors, Wavefront sensors, Error analysis, Mirrors, Control systems, Telescopes, Actuators, Motion models

Read Abstract +

Proceedings Article | 5 August 2010 Paper

Wavefront controls for a large submillimeter-wave observatory

David Redding, John Lou, Andy Kissil, Matt Bradford, Steve Padin, David Woody

Proceedings Volume 7733, 773329 (2010) https://doi.org/10.1117/12.858097

KEYWORDS: Control systems, Error analysis, Telescopes, Sensors, Wavefronts, Actuators, Optical testing, Monte Carlo methods, Mirrors, Filtering (signal processing)

Read Abstract +

Proceedings Article | 23 July 2010 Paper

Phase retrieval methods for wavefront sensing

Siddarayappa Bikkannavar, David Redding, Joseph Green, Scott Basinger, David Cohen, John Lou, Catherine Ohara, Fang Shi

Proceedings Volume 7739, 77392X (2010) https://doi.org/10.1117/12.858980

KEYWORDS: Point spread functions, Phase retrieval, Magnesium, Wavefront sensors, Error analysis, Space telescopes, Spatial frequencies, Image processing, Wavefronts, High dynamic range imaging

Read Abstract +

Proceedings Article | 20 August 2009 Paper

Performance sensitivity studies on the PIAA implementation of the High Contrast Imaging Testbed

Erkin Sidick, John Lou, Stuart Shaklan, Marie Levine

Proceedings Volume 7440, 74400I (2009) https://doi.org/10.1117/12.824696

KEYWORDS: Point spread functions, Wavefronts, Error analysis, Actuators, Near field optics, Coronagraphy, Control systems, 3D modeling, Apodization, Mirrors

Read Abstract +

Proceedings Article | 12 July 2008 Paper

Telescope multi-field wavefront control with a Kalman filter

John Lou, David Redding, Norbert Sigrist, Scott Basigner

Proceedings Volume 7010, 701043 (2008) https://doi.org/10.1117/12.788198

KEYWORDS: Wavefronts, Telescopes, Space telescopes, Phase modulation, Error analysis, Optical alignment, Cameras, Mirrors, Control systems, Filtering (signal processing)

Read Abstract +

Proceedings Article | 20 October 2005 Paper

Optical system alignment via optical state estimation using wavefront measurements

Norbert Sigrist, David Redding, John Lou, Yan Zhang, Scott Basinger

Proceedings Volume 5965, 596524 (2005) https://doi.org/10.1117/12.630886

KEYWORDS: Wavefronts, Optical testing, James Webb Space Telescope, Optical alignment, Error analysis, Space telescopes, Phase modulation, Mirrors, Telescopes, Metrology

Read Abstract +

Proceedings Article | 24 August 2005 Paper

JWST on-orbit multi-field wavefront control with a Kalman filter

John Lou, David Redding, Norbert Sigrist, Yan Zhang, Scott Basinger

Proceedings Volume 5867, 58670T (2005) https://doi.org/10.1117/12.615383

KEYWORDS: James Webb Space Telescope, Wavefronts, Error analysis, Phase modulation, Optical alignment, Telescopes, Space telescopes, Filtering (signal processing), Monte Carlo methods, Control systems

Read Abstract +

Proceedings Article | 14 October 2004 Paper

Optical state estimation using wavefront data

David Redding, Norbert Sigrist, John Lou, Yan Zhang, Paul Atcheson, Daniel Acton, William Hayden

Proceedings Volume 5523, (2004) https://doi.org/10.1117/12.561142

KEYWORDS: Error analysis, James Webb Space Telescope, Wavefronts, Telescopes, Phase modulation, Space telescopes, Optical testing, Interferometers, Actuators, Monte Carlo methods

Read Abstract +

Proceedings Article | 11 March 1993 Paper

Applications development of the Intel iWarp system

John Lou

Proceedings Volume 1964, (1993) https://doi.org/10.1117/12.141771

KEYWORDS: Image processing, Evolutionary algorithms, Signal processing, Computer programming, Computing systems, Data processing, Telecommunications, Wavefronts, Data communications, Artificial intelligence

Read Abstract +

Showing 5 of 14 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years