Geometry of the NIRSpec aperture plane, including the four MSA quadrants (frame in blue, shutters as a grey checkerboard), the fixed slits and IFU aperture (all in black). Each quadrant, labelled Q1 through Q4, contains 365 × 171 shutters. The projected locations of the detector arrays are shown in green, with green dotted lines indicating their extent and hence where the gap between detectors is hidden in the figure by the MSA. The red dashed rectangle marks the ~3′6 × 3′4 on-sky field-of-view, constrained by a field stop at the entrance of the instrument.