Mr. Koby Z. Smith Profile

Koby Z. Smith

Principal Optical Engineer

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Author

Publications (18)

Proceedings Article | 4 October 2023 Presentation + Paper

Opto-mechanical design, alignment, and test of the SPHEREx telescope: a cryogenic all-aluminum freeform system for the astrophysics medium explorer mission

Eric Frater, Chris Seckar, Jeffrey Wedmore, Elliott Jenks, Owen Lincoln, Koby Smith

Proceedings Volume 12676, 126760S (2023) https://doi.org/10.1117/12.2682014

KEYWORDS: Telescopes, Mirrors, Optical alignment, Cryogenics, Short wave infrared radiation, Design and modelling, Optical surfaces, Alloys, Mirror surfaces, Data modeling

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Proceedings Article | 12 July 2018 Paper

Characterization and calibration of the James Webb space telescope mirror actuators fine stage motion

Taylor Chonis, Ben Gallagher, J. Scott Knight, D. Scott Acton, Koby Smith, Erin Wolf, Eric Coppock, James Tersigni, Thomas Comeau

Proceedings Volume 10698, 106983S (2018) https://doi.org/10.1117/12.2311815

KEYWORDS: Actuators, Mirrors, Error analysis, Monte Carlo methods, James Webb Space Telescope, Sensors, Calibration, Space telescopes

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The James Webb Space Telescope’s (Webb’s) deployable primary and secondary mirrors are actively controlled to achieve and maintain precise optical alignment on-orbit. Each of the 18 primary mirror segment assemblies (PMSAs) and the secondary mirror assembly (SMA) are controlled in six degrees of freedom by using six linear actuators in a hexapod arrangement. In addition, each PMSA contains a seventh actuator that adjusts radius of curvature (RoC). The actuators are of a novel stepper motor-based cryogenic two-stage design that is capable of sub-10 nm motion accuracy over a 20 mm range. The nm-level motion of the 132 actuators were carefully tested and characterized before integration into the mirror assemblies. Using these test results as an initial condition, knowledge of each actuator’s length (and therefore mirror position) has relied on software bookkeeping and configuration control to keep an accurate motor step count from which actuator position can be calculated. These operations have been carefully performed through years of Webb test operations using both ground support actuator control software as well as the flight Mirror Control Software (MCS). While the actuator’s coarse stage length is cross-checked using a linear variable differential transformer (LVDT), no on-board cross-check exists for the nm-level length changes of the actuators’ fine stage. To ensure that the software bookkeeping of motor step count is still accurate after years of testing and to test that the actuator position knowledge was properly handed off from the ground software to the flight MCS, a series of optical tests were devised and performed through the Center of Curvature (CoC) ambient optical test campaigns at the Goddard Space Flight Center (GSFC) and during the thermal-vacuum tests of the entire optical payload that were conducted in Chamber A at Johnson Space Center (JSC). In each test, the actuator Fine Step Count (FSC) value is compared to an external measurement provided by an optical metrology tool with the goal of either confirming the MCS database value, or providing a recommendation for an updated calibration if the measured FSC differs significantly from the MCS-based expectation. During ambient testing of the PMSA hexapods, the nm-level actuator length changes were measured with a custom laser deflectometer by measuring tilts of the PMSA. The PMSA RoC fine stage characterization was performed at JSC using multi-wave interferometric measurements with the CoC Optical Assembly (COCOA). Finally, the SMA hexapod fine stage characterization test was performed at JSC using the NIRCam instrument in the “pass-and-a-half” test configuration using a test source from the Aft-Optics System Source Plate Assembly (ASPA). In this paper, each of these three tests, subsequent data analyses, and uncertainty estimations will be presented. Additionally, a summary of the ensemble state of Webb’s actuator fine stages is provided, along with a comparison to a Wavefront Sensing and Control (WFSC)-based requirement for FSC errors as they relate to the optical alignment convergence of the telescope on-orbit.

Proceedings Article | 10 July 2018 Presentation + Paper

Optical assessment of the James Webb Space telescope primary and secondary mirror cryogenic alignment with a Hartmann test

Laura Coyle, Taylor Chonis, Koby Smith, J. Scott Knight, D. Scott Acton, Joseph Howard, Lee Feinberg

Proceedings Volume 10706, 107061Q (2018) https://doi.org/10.1117/12.2312201

KEYWORDS: Mirrors, Point spread functions, Optical alignment, James Webb Space Telescope, Space telescopes, Telescopes, Cryogenics, Monte Carlo methods

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Proceedings Article | 6 July 2018 Paper

Wavefront sensing and controls demo during the cryo-vac testing of JWST

D. Scott Acton, J. Knight, Taylor Chonis, Laura Coyle, Koby Smith, Eric Coppock, Charles-Philippe Lajoie, Marshall Perrin, Conrad Wells, James Hadaway

Proceedings Volume 10698, 106983P (2018) https://doi.org/10.1117/12.2315396

KEYWORDS: Image segmentation, James Webb Space Telescope, Space telescopes, Wavefronts, Telescopes, Wavefront sensors, Control systems, Mirrors, Image processing, Sensors

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Proceedings Article | 6 July 2018 Paper

JWST optical telescope element center of curvature test

Babak Saif, Ritva Keski-Kuha, David Chaney, Perry Greenfield, Kyle Van Gorkom, Keira Brooks, Warren Hack, Marcel Bluth, Josh Bluth, James Sanders, Koby Smith, Larkin Carey, Sze Chaung, Lee Feinberg, Severine Tournois, W. Scott Smith, Vladimir Kradinov

Proceedings Volume 10698, 106983M (2018) https://doi.org/10.1117/12.2313029

KEYWORDS: Mirrors, Space telescopes, Monochromatic aberrations, James Webb Space Telescope, Computer generated holography, Telescopes, Interferometers, Optical testing, Optical alignment, Optical fabrication

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Proceedings Article | 6 July 2018 Presentation + Paper

JWST mirror and actuator performance at cryo-vacuum

Erin Wolf, Benjamin Gallagher, J. Scott Knight, Taylor Chonis, Joseph Sullivan, Koby Smith, Andrew Rudeen, Kevin Babcock, Bruce Hardy, Allison Barto, Eric Coppock, Clinton Davis

Proceedings Volume 10698, 1069808 (2018) https://doi.org/10.1117/12.2312872

KEYWORDS: Actuators, Mirrors, James Webb Space Telescope, Phase shifts, Space telescopes, Cryogenics, Telescopes, Observatories, Segmented mirrors

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Proceedings Article | 6 July 2018 Presentation + Paper

James Webb Space Telescope optical performance predictions post cryogenic vacuum tests

Paul Lightsey, J. Scott Knight, Allison Barto, Koby Smith, Taylor Chonis, Laura Coyle, Scott Acton, Scott Rohrbach, Kim Mehalick, Lee Feinberg, William Hayden, Charles Atkinson, Conrad Wells, James Hadaway

Proceedings Volume 10698, 1069804 (2018) https://doi.org/10.1117/12.2312276

KEYWORDS: Adaptive optics, Mirrors, James Webb Space Telescope, Cryogenics, Telescopes, Optical alignment, Space telescopes, Photogrammetry, Monte Carlo methods, Actuators

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Proceedings Article | 5 September 2017 Presentation + Paper

JWST center of curvature test method and results

Babak Saif, David Chaney, Perry Greenfield, Kyle Van Gorkom, Keira Brooks, Warren Hack, Marcel Bluth, Josh Bluth, James Sanders, Koby Smith, Larkin Carey, Sze Chaung, Ritva Keski-Kuha, Lee Feinberg, Severine Tournois, W. Scott Smith, Vladimir Kradinov

Proceedings Volume 10401, 104010T (2017) https://doi.org/10.1117/12.2273974

KEYWORDS: James Webb Space Telescope, Mirrors, Space telescopes, Telescopes, Interferometers, Metrology, Optical fabrication equipment, Optical telescopes, Optical components, Optical fabrication

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Proceedings Article | 29 July 2016 Paper

Hartmann test for the James Webb Space Telescope

J. Scott Knight, Lee Feinberg, Joseph Howard, D. Scott Acton, Tony Whitman, Koby Smith

Proceedings Volume 9904, 99040C (2016) https://doi.org/10.1117/12.2233114

KEYWORDS: James Webb Space Telescope, Space telescopes, Phase retrieval, Telescopes, Optical testing, Cryogenics, Mirrors, Wavefronts, Image segmentation, Adaptive optics

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Proceedings Article | 29 July 2016 Paper

Calibration results using highly aberrated images for aligning the JWST instruments to the telescope

Koby Smith, D. Scott Acton, Ben Gallagher, J. Scott Knight, Bruce Dean, Alden Jurling, Thomas Zielinski

Proceedings Volume 9904, 990442 (2016) https://doi.org/10.1117/12.2232180

KEYWORDS: James Webb Space Telescope, Mirrors, Calibration, Phase retrieval, Adaptive optics, Point spread functions, Image processing, Metrology, Wavefronts, Charge-coupled devices

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The James Webb Space Telescope (JWST) project is an international collaboration led by NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, MD. JWST is NASA’s flagship observatory that will operate nearly a million miles away from Earth at the L2 Lagrange point. JWST’s optical design is a three-mirror anastigmat with four main optical components; 1) the eighteen Primary Mirror Segment Assemblies (PMSA), 2) a single Secondary Mirror Assembly (SMA), 3) an Aft-Optics Subsystem (AOS) consisting of a Tertiary Mirror and Fine Steering Mirror, and 4) an Integrated Science Instrument Module consisting of the various instruments for JWST. JWST’s optical system has been designed to accommodate a significant amount of alignment capability and risk with the PMSAs and SMA having rigid body motion available on-orbit just for alignment purposes. However, the Aft-Optics Subsystem (AOS) and Integrated Science Instrument Module (ISIM) are essentially fixed optical subsystems within JWST, and therefore the cryogenic alignment of the AOS to the ISIM is critical to the optical performance and mission success of JWST.
In support of this cryogenic alignment of the AOS to ISIM, an array of fiber optic sources, known as the AOS Source Plate Assembly (ASPA), are placed near the intermediate image location of JWST (between the secondary and tertiary mirrors) during thermal vacuum ground-test operations. The AOS produces images of the ASPA fiber optic sources at the JWST focal surface location, where they are captured by the various science instruments. In this manner, the AOS provides an optical yardstick by which the instruments within ISIM can evaluate their relative positions to and the alignment of the AOS to ISIM can be quantified. However, since the ASPA is located at the intermediate image location of the JWST three-mirror anastigmat design, the images of these fiber optic sources produced by the AOS are highly aberrated with approximately 2-3μm RMS wavefront error consisting mostly of 3rd-order astigmatism and coma. This is because the elliptical tertiary mirror of the AOS is used off of its ideal foci locations without the compensating wavefront effects of the JWST primary and secondary mirrors. Therefore, the PSFs created are highly asymmetric with relatively complex structure and the centroid and encircled energy analyses traditionally used to locate images are not sufficient for ensuring the AOS to ISIM alignment.
A novel approach combining phase retrieval and spatial metrology was developed to both locate the images with respect to the AOS and provide calibration information for eventual AOS to ISIM alignment verification. During final JWST OTE and ISIM (OTIS) testing, only a single thru-focus image will be collected by the instruments. Therefore, tools and processes were developed to perform single-image phase retrieval on these highly aberrated images such that any single image of the ASPA source can provide calibrated knowledge of the instruments’ position relative to the AOS. This paper discusses the results of the methodology, hardware, and calibration performed to ensure that the AOS and ISIM are aligned within their respective tolerances at JWST OTIS testing.

Proceedings Article | 21 September 2012 Paper

Statistical analysis of the surface figure of the James Webb Space Telescope

Paul Lightsey, David Chaney, Benjamin Gallagher, Bob Brown, Koby Smith, John Schwenker

Proceedings Volume 8442, 84422F (2012) https://doi.org/10.1117/12.924836

KEYWORDS: Mirrors, Spatial frequencies, Monochromatic aberrations, James Webb Space Telescope, Cryogenics, Shape memory alloys, Metrology, Statistical analysis, Polishing, Space telescopes

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Proceedings Article | 27 September 2011 Paper

Cryogenic optical testing results of JWST aspheric test plate lens

Koby Smith, Timothy Towell

Proceedings Volume 8126, 81260O (2011) https://doi.org/10.1117/12.889150

KEYWORDS: Computer generated holography, Monochromatic aberrations, Cryogenics, Optical testing, Shape memory alloys, James Webb Space Telescope, Distance measurement, Temperature metrology, Helium, Optical fabrication

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Proceedings Article | 27 September 2011 Paper

Electronic speckle pattern interferometric testing of JWST primary mirror segment assembly

Koby Smith, David Chaney, Babak Saif

Proceedings Volume 8126, 81260N (2011) https://doi.org/10.1117/12.889142

KEYWORDS: Mirrors, Optical fabrication, Speckle pattern, James Webb Space Telescope, Surface finishing, Optical testing, Interferometers, Acoustics, Speckle, Interferometry

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Proceedings Article | 15 September 2011 Paper

JWST mirror production status

Benjamin Gallagher, Mark Bergeland, Bob Brown, David Chaney, Tracy Copp, Jake Lewis, Brad Shogrin, Koby Smith, Jeff Sokol, James Hadaway, Holger Glatzel, Patrick Johnson, Allen Lee, Dan Patriarca, Ian Stevenson, Jason Cluney, Tom Parsonage, Jeff Calvert, Brady Rodgers, Andy McKay, Scott Texter, Lester Cohen, Lee Feinberg

Proceedings Volume 8146, 814607 (2011) https://doi.org/10.1117/12.892326

KEYWORDS: Mirrors, James Webb Space Telescope, Coating, Cryogenics, Polishing, Surface finishing, Aerospace engineering, Beryllium, Manufacturing, Composites

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Proceedings Article | 5 August 2010 Paper

Optical performance for the actively controlled James Webb Space Telescope

Paul Lightsey, Dave Chaney, Ben Gallagher, Bob Brown, Koby Smith, Jake Lewis, Allison Barto, Scott Knight, Scott Acton, Chris Stewart, Noah Siegel

Proceedings Volume 7731, 77310B (2010) https://doi.org/10.1117/12.859091

KEYWORDS: Mirrors, James Webb Space Telescope, Telescopes, Space telescopes, Polishing, Shape memory alloys, Cryogenics, Image segmentation, Spatial frequencies, Wavefront sensors

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Proceedings Article | 3 August 2010 Paper

Survey of interferometric techniques used to test JWST optical components

H. Philip Stahl, Chris Alongi, Andrea Arneson, Rob Bernier, Bob Brown, Dave Chaney, Glen Cole, Jay Daniel, Lee Dettmann, Ron Eng, Ben Gallagher, Robert Garfield, James Hadaway, Patrick Johnson, Allen Lee, Doug Leviton, Adam Magruder, Michael Messerly, Ankit Patel, Pat Reardon, John Schwenker, Martin Seilonen, Koby Smith, W. Scott Smith

Proceedings Volume 7790, 779002 (2010) https://doi.org/10.1117/12.862234

KEYWORDS: Mirrors, Interferometers, Metrology, James Webb Space Telescope, Optical testing, Computer generated holography, Optical components, Cryogenics, Interferometry, Optical fabrication

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Proceedings Article | 24 September 2004 Paper

Current concepts for cryogenic optical testing of the JWST secondary mirror

Koby Smith, John Schwenker, Robert Brown, Joseph Sullivan

Proceedings Volume 5494, (2004) https://doi.org/10.1117/12.554420

KEYWORDS: Mirrors, James Webb Space Telescope, Optical spheres, Cryogenics, Optical testing, Aspheric lenses, Wavefronts, Aerospace engineering, Spherical lenses, Tolerancing

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Proceedings Article | 27 December 2001 Paper

Development of optimal grinding and polishing tools for aspheric surfaces

James Burge, Bill Anderson, Scott Benjamin, Myung K. Cho, Koby Smith, Martin Valente

Proceedings Volume 4451, (2001) https://doi.org/10.1117/12.453615

KEYWORDS: Surface finishing, Polishing, Aspheric lenses, Monochromatic aberrations, Spherical lenses, Optics manufacturing, Metals, Interfaces, Aluminum, Finite element methods

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Showing 5 of 18 publications

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