Verification of the James Webb Space Telescope (JWST) wavefront sensing and control system

Contos, Adam R.; Acton, D. Scott; Barto, Allison; Burns, Laura A.; Contreras, James; Dean, Bruce H.; Elliott, Erin; Feinberg, Lee; Hansen, Knud Erik; Hardy, Bruce; Hayden, William L.; Knight, J. Scott; Lightsey, Paul A.; Starr, Carl; Sullivan, Joseph

doi:10.1117/12.786984

Cited by 19 publications

(13 citation statements)

References 6 publications

(6 reference statements)

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“…The dispersed Hartman coarse phasing process was demonstrated on the Keck telescope (Albanese 2006). The overall flight wavefront sensing and control process has been demonstrated on a 1/6 scale fully functional model (Figure 7) of the JWST telescope (Feinberg 2007, Contos 2008). …”

Section: Collecting the First Lightmentioning

confidence: 98%

The JWST science instrument payload: mission context and status

Greenhouse

2014

SPIE Proceedings

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The James Webb Space Telescope (JWST) is the scientific successor to the Hubble Space Telescope. It is a cryogenic infrared space observatory with a 25 m 2 aperture (6 m class) telescope that will achieve diffraction limited angular resolution at a wavelength of 2 um. The science instrument payload includes four passively cooled near-infrared instruments providing broad-and narrow-band imagery, coronography, as well as multi-object and integral-field spectroscopy over the 0.6 < λ < 5.0 um spectrum. An actively cooled mid-infrared instrument provides broad-band imagery, coronography, and integral-field spectroscopy over the 5.0 < λ < 29 um spectrum. The JWST is being developed by NASA, in partnership with the European and Canadian Space Agencies, as a general user facility with science observations to be proposed by the international astronomical community in a manner similar to the Hubble Space Telescope. Technology development and mission design are complete. Construction, integration and verification testing is underway in all areas of the program. The JWST is on schedule for launch during 2018. This science case forms the basis from which detailed science and mission requirements were derived to guide engineering design and development of the JWST as a research tool. The science observations that are implemented by the JWST will be proposed by the international astronomical community in response to annual peer reviewed proposal opportunities (Rigby 2012). The discovery potential of the JWST relative to other concurrent facilities is discussed in Thronson, Stiavelli, and Tielens 2009. The emergence of the first sources of light in the universe marks the end of the "Dark Ages" in cosmic history (Rees 1997). The ultraviolet radiation field produced by these sources created the ionization that is observed in the local intergalactic medium (IGM). The JWST design provides unique capability to address key questions about this era in cosmic evolution including: what is the nature of the first galaxies; how and when did ionization of the space between them occur; and what sources caused the ionization? The JWST architecture is primarily shaped by requirements associated with answering the above questions.In contrast to the Hubble Space Telescope (HST), the JWST is designed as an infrared optimized telescope to observe the redshifted visible and ultraviolet radiation from the first galaxies and supernovae of the first stars. To achieve the nJy sensitivity needed to observe this era (z ~ 6-20), the observatory must have a telescope aperture that is larger in diameter than the largest rocket faring, and the entire optical system must be cooled to ~40-50 K. Finally, the resulting large deployable cryogenic telescope must achieve HST-like angular resolution, but at a 4X longer wavelength thus, also necessitating a large diameter telescope aperture. The major observatory design features (Table 1, Figure 1) trace directly from these requirements and differ markedly from those of the HST.

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Section: Collecting the First Lightmentioning

confidence: 98%

The JWST science instrument payload: mission context and status

Greenhouse

2014

SPIE Proceedings

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“…The PMSA placement requirements specify the piston, decenter, tilt and clocking of each segment with respect to a coordinate system defined by the AMAF. Because the telescope is aligned on orbit using wavefront sensing and control, [3] [4] the placement requirements are not exceptionally tight from a precision optics standpoint, but are challenging nonetheless because of the size and scope of the effort. Table 1 illustrates the PMSA tilt verification budget and tilt placement error budget.…”

Section: Primary Mirror Integration Coordinate Systemmentioning

confidence: 99%

Primary mirror segment assembly integration and alignment for the James Webb Space Telescope

et al. 2010

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The Optical Telescope Element (OTE) consists of a 6.6 m, all-reflective, three-mirror anastigmat. The 18-segment primary mirror (PM) presents unique and challenging assembly, integration and alignment verification requirements. Each mirror segment is mechanically integrated with the Primary Mirror Backplane Support Structure (PMBSS) using compound angle shims to compensate for global alignment and local co-planarity errors. The processes used to determine the mechanical shim prescription, primary mirror alignment and integration, and placement verification are discussed. In an effort to reduce process uncertainty and program risk, the JWST program recently conducted a PMSA Integration Demonstration at ITT. Through this activity, full scale demonstrations of the Ground Support Equipment (GSE) and critical integration processes were successfully completed. The results of these demonstrations indicate that the equipment, processes, and procedures developed by ITT meet the critical requirements for PMSA placement.

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“…Webb SLOM is among other optical control simulation tools that have been developed by the JWST optical modeling community. 10,11 STScI has developed an optical control modeling capability to engage in the optical control simulation and modeling verification analysis and discussion within the JWST community. Simulation of optical control strategy and wavefront commissioning plans is an essential component of the STScI role in the JWST mission.…”

Section: Optical Control Modelmentioning

confidence: 99%

Presentation, analysis, and simulation of active alignment strategies for the James Webb Space Telescope

Upton

2009

SPIE Proceedings

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This paper presents three characteristics in the simulated active alignment strategy of the James Webb Space Telescope. The first includes the analysis and comparison of a baseline active alignment strategy with a damped least squares strategy. This baseline utilizes prior knowledge by means of direct human operator interaction to engage sets of telescope compensators to target specific aberration signatures. The baseline is compared to a damped least-squares strategy that utilizes simultaneous engagement of all telescope compensators without explicit human operator interaction to achieve a least-squares telescope compensation. Second, we discuss how the active alignment of the JWST is encapsulated in a linear optical model developed at the Space Telescope Science Institute. This linear optical model provides a framework for an efficient and robust description of the optical control properties of the JWST and clearly articulates the necessity for having a multi-instrument multifield wavefront sensing strategy to overcome control system non independence and the effects of non-common path errors in the main wavefront sensing camera. Finally, we present analytical results that explicitly map the telescope wavefront responses to the telescope control modes, and we present Monte-Carlo optical performance simulation results that demonstrate the efficacy of the damped least-squares active alignment and the priorknowledge active alignment schemes.

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Verification of the James Webb Space Telescope (JWST) wavefront sensing and control system

Cited by 19 publications

References 6 publications

The JWST science instrument payload: mission context and status

The JWST science instrument payload: mission context and status

Primary mirror segment assembly integration and alignment for the James Webb Space Telescope

Presentation, analysis, and simulation of active alignment strategies for the James Webb Space Telescope

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