Spectroscopic Modes Spectrum Image
NIRISS and NIRCam offer complementary Wide-Field Slitless Spectroscopy (WFSS) modes.
NIRCam is also equipped with a WFSS mode with a resolving power of λ/Δλ~1600 at 2.4-5.0 μm in the long-wavelength channel. In the WFSS mode, the short-wavelength channel is used to obtain imaging of the same field-of-view. Similar to NIRISS WFSS, two grisms with perpendicular dispersion directions are available to help separating overlapping spectra.
NIRISS has a WFSS mode with resolving powers of λ/Δλ~150) between 0.8–2.2 μm, over a 2.2’x2.2’ field-of-view. This mode can be used efficiently in parallel with other instruments. The NIRISS WFSS mode uses a pair of identical grisms with perpendicular dispersion directions. Data acquired with both dispersion directions helps to disentangle blended spectra in crowded fields.