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James Webb Space Telescope
NIRISS Single-Object Slitless Spectroscopy

GR700XD Design and Spectrum

The figures below show the components and the spectrum for Single-Object Slitless Spectroscopy. The components consist of

The direction of defocus is rotated by 2 degrees relative to the detector pixels to mitigate undersampling of the PSF in the spectral direction.

See the sensitivity of the NIRISS in its SOSS mode.

GR700XD design
GR700XD spectrum

Dual Wheel Configuration for Single-Object Slitless Spectroscopy

In SOSS mode the GR700XD grism (highlighted in green) in the Pupil Wheel may be used only with the Filter Wheel in the CLEAR position (highlighted in green).

Dual wheel configuration for Single-Object Slitless Spectroscopy