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

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

doi:10.1117/12.2315396

Cited by 8 publications

(6 citation statements)

References 1 publication

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“…During OTIS CV, the functionality of the mirror move commanding process was also exercised to demonstrate the WFSC process, using the flight data acquisition scripts and flight wavefront analysis software 6 .…”

Section: Test Campaignmentioning

confidence: 99%

JWST mirror and actuator performance at cryo-vacuum

Wolf

Gallagher

Knight

et al. 2018

Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

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The James Webb Space Telescope (JWST) telescope's Secondary Mirror Assembly (SMA) and eighteen Primary Mirror Segment Assemblies (PMSAs) are each actively controlled in rigid body position via six hexapod actuators. Each of the PMSAs additionally has a radius of curvature actuator. The mirrors are stowed to the mirror support structure to survive the launch environment and then must be deployed 12.5 mm to reach the nominally deployed position before the Wavefront Sensing & Control (WFSC) alignment and phasing process begins. JWST requires testing of the full optical system in a Cryogenic Vacuum (CV) environment before launch. The cryo vacuum test campaign was executed in Chamber A at the Johnson Space Center (JSC) in Houston Texas. The test campaign consisted of an ambient vacuum test, a cooldown test, a cryo stable test at 65 Kelvin, a warmup test, and finally a second ambient vacuum test. Part of that test campaign was the functional and performance testing of the hexapod actuators on the flight mirrors. This paper will describe the testing that was performed on all 132 hexapod and radius of curvature actuators. The test campaign first tests actuators individually then tested how the actuators perform in the hexapod system. Telemetry from flight sensors on the actuators and measurements from external metrology devices such as interferometers, photogrammetry systems and image analysis was used to demonstrate the performance of the JWST actuators. The mirror move commanding process was exercised extensively during the JSC CV test and many examples of accurately commanded moves occurred. The PMSA and SMA actuators performed extremely well during the JSC CV test, and we have demonstrated that the actuators are fully functional both at ambient and cryo temperatures and that the mirrors will go to their commanded positions with the accuracy needed to phase and align the telescope.

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Section: Test Campaignmentioning

confidence: 99%

JWST mirror and actuator performance at cryo-vacuum

Wolf

Gallagher

Knight

et al. 2018

Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

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“…Stabilization, disturbance rejection, and precise control of optical beams and optical spots are fundamental and ubiquitous problems that appear in a number of applications and optical systems. For example, these problems are crucial for the development of sensing and control systems for space and ground optical telescopes, [1][2][3][4][5][6][7][8][9][10][11][12] freespace optical communication terminals, 13,14 turbulence compensation systems, 13 precise laser beam steering and jitter compensation systems, 15,16,[16][17][18][19][20][21] and for other optical instruments and devices. [22][23][24][25][26][27] Optical spot and wave-front disturbances can originate from various sources and phenomena.…”

Section: Introductionmentioning

confidence: 99%

Data-driven Estimation, Tracking, and System Identification of Deterministic and Stochastic Optical Spot Dynamics

Haber¹,

Krainak²

2023

Preprint

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Stabilization, disturbance rejection, and control of optical beams and optical spots are ubiquitous problems that are crucial for the development of optical systems for ground and space telescopes, free-space optical communication terminals, precise beam steering systems, and other types of optical systems. High-performance disturbance rejection and control of optical spots require the development of disturbance estimation and datadriven Kalman filter methods. Motivated by this, we propose a unified and experimentally verified data-driven framework for optical-spot disturbance modeling and tuning of covariance matrices of Kalman filters. Our approach is based on covariance estimation, nonlinear optimization, and subspace identification methods. Also, we use spectral factorization methods to emulate optical-spot disturbances with a desired power spectral density in an optical laboratory environment. We test the effectiveness of the proposed approaches on an experimental setup consisting of a piezo tip-tilt mirror, piezo linear actuator, and a CMOS camera.

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“…7 Most recently, WFS&C methods have been demonstrated on the integrated flight hardware. 8,9 However, during the decade-plus development of JWST, WFS&C algorithms have continued to develop, and new advanced algorithms are worth investigating to expand the toolkit for alignment and maintenance of JWST.…”

Section: Introductionmentioning

confidence: 99%

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

Laginja¹,

Brady

Soummer

et al. 2018

Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

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The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a hardware simulator for wavefront sensing and control designed to produce JWST-like images. A model of the JWST three mirror anastigmat is realized with three lenses in the form of a Cooke triplet, which provides JWST-like optical quality over a field equivalent to a NIRCam module. An Iris AO hexagonally segmented mirror stands in for the JWST primary. This setup successfully produces images extremely similar to expected JWST in-flight point spread functions (PSFs), and NIRCam images from cryotesting, in terms of the PSF morphology and sampling relative to the diffraction limit. The segmentation of the primary mirror into subapertures introduces complexity into wavefront sensing and control (WFS&C) of large space based telescopes like JWST. JOST provides a platform for independent analysis of WFS&C scenarios for both commissioning and maintenance activities on such observatories. We present an update of the current status of the testbed including both single field and wide-field alignment results. We assess the optical quality of JOST over a wide field of view to inform the future implementation of different wavefront sensing algorithms including the currently implemented Linearized Algorithm for Phase Diversity (LAPD). JOST complements other work at the Makidon Laboratory at the Space Telescope Science Institute, including the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed, that investigates coronagraphy for segmented aperture telescopes. Beyond JWST we intend to use JOST for WFS&C studies for future large segmented space telescopes such as LUVOIR.

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

Cited by 8 publications

References 1 publication

JWST mirror and actuator performance at cryo-vacuum

JWST mirror and actuator performance at cryo-vacuum

Data-driven Estimation, Tracking, and System Identification of Deterministic and Stochastic Optical Spot Dynamics

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

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