Geometry of the NIRSpec field of view. In the entrance focal plane, it is limited by the field stop (dashed red line), which is slightly undersized with respect to the microshutter array (dark gray filled squares). The metal frame holding the four quadrants has cutouts for the fixed slits and the IFU aperture. The two sensor chip assemblies (SCAs) populating the NIRSpec focal plane assembly (FPA) are over-plotted (large light gray open squares). Also shown are the locations of the 30 undispersed slice images on the detector, i.e., where they would appear if the MIRROR position were used instead of a disperser. It should be noted that the IFU spectra fall onto the same detector area as those of open microshutters, which is why the IFS and MOS modes of NIRSpec are, in general, mutually exclusive (see discussion in Sect. 2.1).