Fabrication and test of silicon grisms for JWST-NIRCam

Jaffe, D. T.; Wang, Wendong; Marsh, Jasmina P.; Deen, C.; Kelly, Douglas; Greene, Thomas P.

doi:10.1117/12.788556

Cited by 6 publications

(4 citation statements)

References 13 publications

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“…We therefore integrate into the discussion of requirements a discussion of measurement techniques and actual results. As a test case, we report the measurement results for a grating produced as one of a batch of six for use in the NIRCam instrument on JWST (Jaffe et al 2008;Gully-Santiago et al 2010).…”

Section: Requirements Metrology and Resultsmentioning

confidence: 99%

“…The Mar paper focuses on design and manufacturing issues for silicon grisms at the device level. In this paper, we present a new generation of Si grisms produced for use in the 2-5 μm range in the NIRCam instrument on James Webb Space Telescope (JWST) (Jaffe et al 2008;Greene et al 2010). These devices have reached a new level of accuracy and optical performance.…”

Section: Introductionmentioning

confidence: 99%

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A Grism Design Review and the As-Built Performance of the Silicon Grisms forJWST-NIRCam

Deen¹,

Gully-Santiago²,

Wang³

et al. 2017

PASP

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Grisms are dispersive transmission optics that find their most frequent use in instruments that combine imaging and spectroscopy. This application is particularly popular in the infrared where imagers frequently have a cold pupil in their optical path that is a suitable location for a dispersive element. In particular, several recent and planned space experiments make use of grisms in slitless spectrographs capable of multi-object spectroscopy. We present an astronomer-oriented general purpose introduction to grisms and their use in current and future astronomical instruments. We present a simple, step-by-step procedure for adding a grism spectroscopy capability to an existing imager design. This procedure serves as an introduction to a discussion of the device performance requirements for grisms, focusing in particular on the problems of lithographically patterned silicon devices, the most effective grism technology for the 1.1-8 micron range. We begin by summarizing the manufacturing process of monolithic silicon gratings. We follow this with a report in detail on the as-built performance of parts constructed for a significant new space application, the NIRCam instrument on JWST and compare these measurements to the requirements.

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Section: Requirements Metrology and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Grism Design Review and the As-Built Performance of the Silicon Grisms forJWST-NIRCam

Deen¹,

Gully-Santiago²,

Wang³

et al. 2017

PASP

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show abstract

“…[1][2][3][4][5] Long wavelength (LW; λ ¼ 2.4 to 5.0 μm) Si grisms 6 and λ ¼ 1 to 2 μm dispersed Hartmann sensors (DHSs) were developed for the purposes of wavefront sensing and telescope primary segment phasing with NIRCam. 7 The DHSs provide R ≡ λ∕δλ ≃ 300 spectra of bright point sources.…”

Section: Introductionmentioning

confidence: 99%

λ = 2.4 to 5 μ m spectroscopy with the James Webb Space Telescope NIRCam instrument

Greene

Kelly

Stansberry

et al. 2017

J. Astron. Telesc. Instrum. Syst

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Abstract. The James Webb Space Telescope near-infrared camera (JWST NIRCam) has two 2. 0 2 × 2. 0 2 fields of view that can be observed with either imaging or spectroscopic modes. Either of two R ∼ 1500 grisms with orthogonal dispersion directions can be used for slitless spectroscopy over λ ¼ 2.4 to 5.0 μm in each module, and shorter wavelength observations of the same fields can be obtained simultaneously. We describe the design drivers and parameters of the grisms and present the latest predicted spectroscopic sensitivities, saturation limits, resolving powers, and wavelength coverage values. Simultaneous short wavelength (0.6 to 2.3 μm) imaging observations of the 2.4 to 5.0 μm spectroscopic field can be performed in one of several different filter bands, either infocus or defocused via weak lenses internal to the NIRCam. The grisms are available for singleobject time-series spectroscopy and wide-field multiobject slitless spectroscopy modes in the first cycle of JWST observations. We present and discuss operational considerations including subarray sizes and data volume limits. Potential scientific uses of the grisms are illustrated with simulated observations of deep extragalactic fields, dark clouds, and transiting exoplanets. Information needed to plan observations using these spectroscopic modes is also provided.

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“…[1][2][3][4] These and other previous works have described its wide-field and coronagraphic imaging capabilities well, but little practical information has been published on using NIRCam in its spectroscopic modes. Long-wave (LW; λ = 2.4−5.0 µm) Si grisms 5 and short-wave (SW; λ = 1−2 µm) Dispersed Hartmann Sensors (DHSs) were developed for the purposes of wavefront sensing and telescope primary segment phasing with NIRCam. 6 The LW grisms have been approved and are being supported for scientific use.…”

Section: Introductionmentioning

confidence: 99%

Slitless spectroscopy with the James Webb Space Telescope Near-Infrared Camera (JWST NIRCam)

et al. 2016

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The James Webb Space Telescope near-infrared camera (JWST NIRCam) has two 2. 2 × 2. 2 fields of view that are capable of either imaging or spectroscopic observations. Either of two R ∼ 1500 grisms with orthogonal dispersion directions can be used for slitless spectroscopy over λ = 2.4 − 5.0 µm in each module, and shorter wavelength observations of the same fields can be obtained simultaneously. We present the latest predicted grism sensitivities, saturation limits, resolving power, and wavelength coverage values based on component measurements, instrument tests, and end-to-end modeling. Short wavelength (0.6 -2.3 µm) imaging observations of the 2.4 -5.0 µm spectroscopic field can be performed in one of several different filter bands, either in-focus or defocused via weak lenses internal to NIRCam. Alternatively, the possibility of 1.0 -2.0 µm spectroscopy (simultaneously with 2.4 -5.0 µm) using dispersed Hartmann sensors (DHSs) is being explored. The grisms, weak lenses, and DHS elements were included in NIRCam primarily for wavefront sensing purposes, but all have significant science applications. Operational considerations including subarray sizes, and data volume limits are also discussed. Finally, we describe spectral simulation tools and illustrate potential scientific uses of the grisms by presenting simulated observations of deep extragalactic fields, galactic dark clouds, and transiting exoplanets.

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Fabrication and test of silicon grisms for JWST-NIRCam

Cited by 6 publications

References 13 publications

A Grism Design Review and the As-Built Performance of the Silicon Grisms forJWST-NIRCam

A Grism Design Review and the As-Built Performance of the Silicon Grisms forJWST-NIRCam

λ = 2.4 to 5 μ m spectroscopy with the James Webb Space Telescope NIRCam instrument

Slitless spectroscopy with the James Webb Space Telescope Near-Infrared Camera (JWST NIRCam)

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