Layout of the NIRSpec Slit Plane. (a) The four quadrants of the Microshutter Array, the five Fixed Slits, the entrance aperture of the Integral Field Unit, and the locations of its 30 virtual slit images. The dispersion direction is horizontal. Black areas in the MSA depict inoperable vignetted or permanently closed shutters. (b) Close-up of the left-most group of four Fixed Slits and the IFU entrance aperture. (c) Close-up of the right-most redundant Fixed Slit.