NIRISS SOSS planning tool

As its name suggests, the Single-Object Slit-less Spectroscopy (SOSS) mode of NIRISS is slit-less and thus the spectrum of a target star may be contaminated by partly overlapping spectra of nearby stars. For a given target, the details of this potential contamination are a function of the Aperture Position Angle (APA) at which the observations are taken. This tool simulates SOSS observations of a given target and produces an estimate of the level of contamination as a function of the APA of the observation; it may be used to plan observations at the optimal APA. The tool also computes the JWST accessibility windows of the target, along with the corresponding accessible PAs for NIRISS observations.

Usage notes:

• The “calculate contamination” button computes both the contamination and the visibility of a target. If you wish, you may calculate only the visibility using the “calculate visibility” button.
• The field stars used for this analysis are retrieved from the 2MASS point source catalogue. Contamination from stars missing from the 2MASS PSC is thus not modelled; this may be important for faint targets.
• For comments and questions, contact david.lafreniere@umontreal.ca