Detectors for the<i>James Webb Space Telescope</i>Near‐Infrared Spectrograph. I. Readout Mode, Noise Model, and Calibration Considerations

Rauscher, Bernard J.; Fox, O.; Ferruit, Pierre; Hill, Robert J.; Waczynski, Augustyn; Wen, Yiting; Xia‐Serafino, Wei; Mott, Brent; Alexander, David; Brambora, Clifford; Derro, Rebecca J.; Engler, Chuck; Garrison, Matthew; Johnson, Thomas E.; Manthripragada, Sridhar S.; Marsh, J. G.; Marshall, C.J.; Martineau, Robert J.; Shakoorzadeh, Kamdin B.; Wilson, Donna; Roher, Wayne D.; Smith, M. D.; Cabelli, Craig A.; Garnett, James D.; Loose, Markus; Wong‐Anglin, Selmer; Zandian, Majid; Cheng, E. S.; Ellis, Timothy A.; Howe, Bryan; Jurado, Miriam; Lee, Ginn; Nieznanski, John; Wallis, P. M.; York, James; Regan, Michael W.; Hall, Donald N. B.; Hodapp, Klaus W.; Böker, Torsten; Marchi, Guido De; Jakobsen, P.; Strada, Paolo

doi:10.1086/520887

Cited by 81 publications

(79 citation statements)

References 20 publications

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“…The integrations are called up-the-ramp because when pixels are illuminated, the 88 up-the-ramp samples follow an approximately straight line with positive slope. For more information on JWST detector readout modes and noise models, the interested reader is referred to Rauscher et al 11 …”

Section: Jwst Nir Performance Requirementsmentioning

confidence: 99%

Commentary: JWST near-infrared detector degradation— finding the problem, fixing the problem, and moving forward

et al. 2012

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The James Webb Space Telescope (JWST) is the successor to the Hubble Space Telescope. JWST will be an infrared-optimized telescope, with an approximately 6.5 m diameter primary mirror, that is located at the Sun-Earth L2 Lagrange point. Three of JWST’s four science instruments use Teledyne HgCdTe HAWAII-2RG (H2RG) near infrared detector arrays. During 2010, the JWST Project noticed that a few of its 5 μm cutoff H2RG detectors were degrading during room temperature storage, and NASA chartered a “Detector Degradation Failure Review Board” (DD-FRB) to investigate. The DD-FRB determined that the root cause was a design flaw that allowed indium to interdiffuse with the gold contacts and migrate into the HgCdTe detector layer. Fortunately, Teledyne already had an improved design that eliminated this degradation mechanism. During early 2012, the improved H2RG design was qualified for flight and JWST began making additional H2RGs. In this article, we present the two public DD-FRB “Executive Summaries” that: (1) determined the root cause of the detector degradation and (2) defined tests to determine whether the existing detectors are qualified for flight. We supplement these with a brief introduction to H2RG detector arrays, some recent measurements showing that the performance of the improved design meets JWST requirements, and a discussion of how the JWST Project is using cryogenic storage to retard the degradation rate of the existing flight spare H2RGs.

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Section: Jwst Nir Performance Requirementsmentioning

confidence: 99%

Commentary: JWST near-infrared detector degradation— finding the problem, fixing the problem, and moving forward

et al. 2012

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“…The NIRCam detectors will be operated in their normal MULTIACCUM modes [21][22][23] during spectroscopic observations. High-precision time-series grism observations of bright objects (e.g., host stars of transiting planets) will likely require the use of a limited detector region to prevent saturation.…”

Section: Spectroscopic Operationsmentioning

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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“…The general expression for the total noise variance, in case of UTR/MACC readout modes, has been provided by Rauscher et al 2007 [10] and is reported hereafter:…”

Section: Vnir Detectors Best Readout Mode Evaluationmentioning

confidence: 99%

Preliminary study of the EChO data sampling and processing

et al. 2014

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The EChO Payload is an integrated spectrometer with six different channels covering the spectral range from the visible up to the thermal infrared. A common Instrument Control Unit (ICU) implements all the instrument control and health monitoring functionalities as well as all the onboard science data processing. To implement an efficient design of the ICU on board software, separate analysis of the unit requirements are needed for the commanding and housekeeping collection as well as for the data acquisition, sampling and compression. In this work we present the results of the analysis carried out to optimize the EChO data acquisition and processing chain.The HgCdTe detectors used for EChO mission allow for non-destructive readout modes, such that the charge may be read without removing it after reading out. These modes can reduce the equivalent readout noise and the gain in signal to noise ratio can be computed using well known relations based on fundamental principles. In particular, we considered a multiaccumulation approach based on non-destructive reading of detector samples taken at equal time intervals. All detectors are periodically reset after a certain number of samples have been acquired and the length of the reset interval, as well as the number of samples and the sampling rate can be adapted to the brightness of the considered source.The estimation of the best set of parameters for the signal to noise ratio optimization and of the best sampling technique has been done by taking into account also the needs of mitigating the expected radiation effects on the acquired data. Cosmic rays can indeed be one of the major sources of data loss for a space observatory, and the studies made for the JWST mission allowed us to evaluate the actual need of the implementation of a dedicated deglitching procedure on board EChO.

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Detectors for theJames Webb Space TelescopeNear‐Infrared Spectrograph. I. Readout Mode, Noise Model, and Calibration Considerations

Cited by 81 publications

References 20 publications

Commentary: JWST near-infrared detector degradation— finding the problem, fixing the problem, and moving forward

Commentary: JWST near-infrared detector degradation— finding the problem, fixing the problem, and moving forward

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

Preliminary study of the EChO data sampling and processing

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