Contamination & Visibility Calculator

This tool is designed for Single-Object Slit-less Spectroscopy (SOSS) mode of NIRISS. For slitless observations, the spectrum of a target star may be contaminated by partlially overlapping spectra of nearby stars. For a given target this contamination depends on the position angle (PA) 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 PA of the observation; it may be used to plan observations at the optimal PA. The tool also computes the JWST accessibility windows of the target, along with the corresponding accessible PAs for NIRISS observations. In the future, functionality will be extended to calculate contamination by other instruments.

Note: 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.

Please omit spaces from target name
If target is unresolved, reload page and enter coordinates manually

The right ascension of the target
The declination of the target

RA offset ("), DEC offset ("), 2MASS J (mag), H (mag) and Ks (mag) [comma separated, no spaces]

PA min
The lower limit on the position angle
PA max
The upper limit on the position angle

This takes about 2 seconds.

This takes more than 2 seconds.