There is a physical gap between the JWST NIRSpec detectors. This affects the IFU observations at high resolutions. The wavelengths that fall in the detector gap are not recoverable. 

JWST's NIRSpec supports integral field spectroscopy with an integral field unit (IFU). Light from the source of interest passes through a small (3" × 3") aperture in the MSA mounting frame and travels through the IFU image slicing mirror optics. Figure 1 shows the location of the IFU aperture on the MSA mounting frame between MSA quadrants 3 and 4. The light then is reflected by mirrors to form an image of the source on the image slicer, which consists of 30 stacked mirror surfaces. Figure 2 shows the layout of the slices, numbered from 0 to 29, within the IFU aperture in the plane of the detector. Figure 1 additionally shows the layout of the slices as positioned on the detector, also numbered 0 to 29.

There is a physical gap between the detectors that can be seen in Figure 1 which depicts the detector array boundaries in white. This gap affects NIRSpec high-resolution IFU observations, resulting in a gap in the wavelength coverage. Unlike other NIRSpec observing modes, wavelength losses due to the gap cannot be fully recovered by dithering within the IFU aperture. The IFU observing mode article provides the approximate spectral wavelengths lost in the detector gap, but the precise values differ for the individual IFU data slices. This article provides additional information on the exact wavelengths lost in the detector wavelength gap per IFU slice for high-resolution IFU observations.