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.
The JWST ETC enables exposure time calculations for a variety of instrument modes, including direct imaging, slitless spectroscopy and integral field unit (IFU), slit spectroscopy, 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 page Creating a JWST ETC Calculation, the next step is to define the strategy to be used for computing the signal-to-noise. The strategies are set using the Strategy tab on the Calculations tab page, and is where the user defines the type of extraction strategy, location of the extraction aperture, and the extraction region size. This tab also provides the options for background subtraction, and allows to set the region from where the background should be extracted.
Please refer to these pages for additional information.
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