3D digital rendering of the instrument cavity. In this orientation the telescope is below the assembly and observing towards the bottom. For clarity, we have added the principal light path and optical components to the rendering; dashed lines are obstructed from the chosen point of view. The large structure to the right of NISP is its outward-facing radiator. It can be clearly seen in the photograph shown in Fig. 5. Figure credit: ADS, annotations by the authors.