INFUSE: Assembly and Alignment of A Rocket-Borne FUV Integral Field Spectrograph

The INtegral Field Ultraviolet Spectroscopic Experiment (INFUSE), a sounding rocket payload under development at the University of Colorado Laboratory for Atmospheric and Space Physics, will be the first far ultraviolet (1000 - 2000 angstrom) integral field spectrograph (IFS) in space. With access to part of the Lyman ultraviolet (1000 - 1216 angstrom), INFUSE will study spectral emission lines such as O VI in extended objects at greater spatial resolution and grasp than has previously been possible. An F/16, 0.49 m Cassegrain telescope feeds the instrument. A 26-element image slicer provided by Canon Inc. forms the basis for the IFS. Each reflective slice acts as a long-slit, creating 26 different channels. Each channel is re-focused and dispersed by one of 26 identical holographic gratings supplied by Horiba JY onto the same 94 x 94 mm cross-strip (XS) microchannel plate detector (MCP). This MCP, provided by Sensor Sciences, will be the largest MCP of its type ever flown in space and will be advancing high event rate photon-counting detector technology for future NASA missions. We discuss the process of aligning the instrument, with a focus on the method by which the 26 gratings are aligned with the image slicer. Additionally, we examine the challenges presented by mounting and coating the large primary mirror and the steps taken to ensure that the mirror remains stable in flight. The first flight of INFUSE is projected for Spring 2023 when it will spectroscopically image the XA region of the Cygnus Loop at the interface between the supernova and the ambient ISM, studying shock fronts in the supernova remnant.