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The JWST Exposure Time Calculator (ETC) reports the results of calculations performed using a specified strategy that includes information about location and size of the extraction aperture, wavelength of interest, and choice of regions for background subtraction.


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The JWST ETC enables exposure time calculations for a variety of instrument modes, including direct imaging, slit spectroscopy, slitless spectroscopy, integral field unit (IFU), and coronagraphy. The signal-to-noise ratio is computed using extraction strategies that are specific to the different modes. After the user has selected the scene, backgrounds, instrument setup, and detector setup, as described in the article Creating a JWST ETC Calculation, the next step is to define the strategy to be used for computing the signal-to-noise. The Strategy tab, shown below, provides choices for the extraction strategy, background subtraction, size and position of the background region, and the wavelength of slice for spectroscopic calculations.

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Figure 1. Location of the strategy tab in the ETC web application

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The strategies are set using the Strategy tab on the Calculations tab page.


Please refer to these pages for additional information on specific extraction strategies.

JWST ETC Imaging Aperture Photometry Strategy
JWST ETC Aperture Spectral Extraction Strategy
JWST ETC MSA Full Shutter Extraction Strategy
JWST ETC IFU Nod In Scene and IFU Nod Off Scene Strategy
JWST ETC SOSS Spectral Extraction Strategy
JWST ETC Coronagraphy Strategy



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References

JWST technical documents

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Last updated

Updated November 5, 2018Published May 5, 2017


  • Updated for ETC v1.3.



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Updated April 05, 2017

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Published March 02, 2017