Intra-pixel response of the new JWST infrared detector arrays

Hardy, Tim; Willot, Chris; Pazder, John

doi:10.1117/12.2057114

Cited by 13 publications

(13 citation statements)

References 4 publications

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“…JexoSim IPRF is generated with l d of 3.7 µm. This approximates the bell-shaped response function measured in Hardy, Willot & Pazder (2014). The IPRF from Hardy, Willot & Pazder (2014) is given for a pixel at 940 nm.…”

Section: Intra-pixel Response Functionmentioning

confidence: 58%

“…If l d is set to ∼ 0 it will approach a 'top hat' function within the confines of the whole pixel area, and thus with no inter-pixel diffusion (Figure 2 A). If l d is set to 3.7 µm we generate a 'bell-shaped' function ( Figure 2 B), which reasonably approximates the profile from Hardy, Willot & Pazder (2014) (Figure 3) 7 . For this study however we have elected to use the top hat function since the bell-shaped function introduces significant charge diffusion contributing to pixel cross-talk.…”

Section: Intra-pixel Response Functionmentioning

confidence: 87%

“…Different positions on the grid capture the variation in the pixel count due to shifts in the image, and this facilitates the pointing jitter simulation described below. Hardy, Willot & Pazder (2014) examined the intra-pixel response of H1RG (5 µm cutoff) detectors for JWST. The pixel response variation was mostly attributed to diffusion of the signal to neighbouring pixels, with a bell-shaped response function with broader wings than a Gaussian.…”

Section: Intra-pixel Response Functionmentioning

confidence: 99%

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JexoSim: a time-domain simulator of exoplanet transit spectroscopy with JWST

Sarkar

Madhusudhan

Παπαγεωργίου

2019

Monthly Notices of the Royal Astronomical Society

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The James Webb Space Telescope (JWST) will perform exoplanet transit spectroscopy in the coming decade promising transformative science results. All four instruments on board can be used for this technique which reconstructs the atmospheric transmission or emission spectrum of an exoplanet from wavelength-dependent light curve measurements. Astrophysical and instrumental noise and systematics can affect the precision and accuracy of the final spectrum, and hence, the atmospheric properties derived from the spectrum. Correlated noise and time-dependent systematics that can bias the measured signal must be accounted for in the final uncertainties. However quantifying these effects can be difficult with real data or simple analytic tools. Existing publicly-available simulators for JWST do not adequately simulate complex time domain processes on exoplanetary transit observations. We report JexoSim, a dedicated time domain simulator for JWST including all four instruments for exoplanet transit spectroscopy. JexoSim models both the astrophysics and the instrument, generating 2-D images in simulated time akin to a real observation. JexoSim can capture correlated noise and systematic biases on the light curve giving it great versatility. Potential applications of JexoSim include performance testing of JWST instruments, assessing science return, and testing data reduction pipelines. We describe JexoSim, validate it against other simulators, and present examples of its utility.

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Section: Intra-pixel Response Functionmentioning

confidence: 58%

Section: Intra-pixel Response Functionmentioning

confidence: 87%

Section: Intra-pixel Response Functionmentioning

confidence: 99%

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JexoSim: a time-domain simulator of exoplanet transit spectroscopy with JWST

Sarkar

Madhusudhan

Παπαγεωργίου

2019

Monthly Notices of the Royal Astronomical Society

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“…Hardy et al (2015) 11 investigated the intra-pixel response of the Hawaii1-RG array for the Faint Guide Star camera on JWST. They found that the largest response variation can be attributed to charge diffusion within the bulk detector materials, while multiple sensitivity holes were observed in ~ 10 % of the pixels.…”

Section: Intra-pixel Sensitivitymentioning

confidence: 99%

Instrument requirements for precision relative astrometry using TMT/IRIS

Suzuki¹,

Harakawa²,

Schoeck³

et al. 2017

Proceedings of the Adaptive Optics for Extremely Large Telescopes 5

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InfraRed Imaging Spectrograph (IRIS) is one of the three instruments that will be available at the first light of TMT. Working with the facility adaptive optics system NFIRAOS, IRIS provides diffraction limited imaging and integral field spectroscopic capabilities in the near-infrared wavelength range. One of the unique observing performances of IRIS is precision relative astrometry at a level of 30 uas. Achieving this unprecedented accuracy necessitates a number of contributing error terms, including target property errors, atmospheric property errors, AO performance errors, optomechanical errors, detector characteristic errors, and data reduction errors, to be reduced by design, calibration, operation, and data reduction. We have created a detailed astrometry error budget which identifies all error terms, quantifies them, and distributes allocations to individual terms to enable the required astrometry accuracy. This error budget is written in terms of astrometric accuracy, i.e., uas, and each error term needs to be translated to technical languages through analyses and simulations when it flows down to system and subsystem requirements. This paper describes the analyses and simulations that we have done to derive the requirements for IRIS with a focus on atmospheric dispersion, optical distortion, and detector characteristics.

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“…Barron et al (2007) and Hardy et al (2014) demonstrated that HgCdTe detectors exhibit subpixel quantum efficiency (QE) variations of several percent in some pixels. While WFIRST will be equipped with more advanced H4RG detectors, spatial offsets of a few percent of the pixel width need to be expected (M. Shao, private comm.).…”

Section: Pixel-level Effectsmentioning

confidence: 99%

In the Crosshair: Astrometric Exoplanet Detection with WFIRST's Diffraction Spikes

Spergel

Lanz

2018

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WFIRST will conduct a coronagraphic program of characterizing the atmospheres of planets around bright nearby stars. When observed with the WFIRST Wide Field Camera, these stars will saturate the detector and produce very strong diffraction spikes. In this paper, we forecast the astrometric precision that WFIRST can achieve by centering on the diffraction spikes of highly saturated stars. This measurement principle is strongly facilitated by the WFIRST H4RG detectors, which confine excess charges within the potential well of saturated pixels. By adopting a simplified analytical model of the diffraction spike caused by a single support strut obscuring the telescope aperture, integrated over the WFIRST pixel size, we predict the performance of this approach with the Fisher-matrix formalism. We discuss the validity of the model and find that 10 µas astrometric precision is achievable with a single 100 s exposure of a R AB = 6 or a J AB = 5 star. We discuss observational limitations from the optical distortion correction and pixel-level artifacts, which need to be calibrated at the level of 10 -20 µas so as to not dominate the error budget. To suppress those systematics, we suggest a series of short exposures, dithered by at least several hundred pixels, to reach an effective per-visit astrometric precision of better than 10 µas. If this can be achieved, a dedicated WFIRST GO program will be able to detect Earth-mass exoplanets with orbital periods of 1 yr around stars within a few pc as well as Neptunelike planets with shorter periods or around more massive or distant stars. Such a program will also enable mass measurements of many anticipated direct-imaging exoplanet targets of the WFIRST coronagraph and a "starshade" occulter.

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Intra-pixel response of the new JWST infrared detector arrays

Cited by 13 publications

References 4 publications

JexoSim: a time-domain simulator of exoplanet transit spectroscopy with JWST

JexoSim: a time-domain simulator of exoplanet transit spectroscopy with JWST

Instrument requirements for precision relative astrometry using TMT/IRIS

In the Crosshair: Astrometric Exoplanet Detection with WFIRST's Diffraction Spikes

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