UV diffraction grating technology maturation plan for the Habitable Worlds Observatory
Journal Article
Overview
abstract
The Astro2020 decadal survey designated a large ultraviolet (UV)/optical/infrared strategic mission, the Habitable Worlds Observatory (HWO), as the top priority for space-based astronomy in the coming decade. HWO will pursue an ambitious program of exoplanetary discovery/characterization and cosmic origin astrophysics. The decadal survey report recognized that many of HWO’s galactic ecosystem, exoplanet, and stellar science goals require high-throughput imaging and spectroscopy at ultraviolet through optical wavelengths (100 to 1000 nm). Early conceptual designs for the UV spectrograph on HWO are based on the LUVOIR and HabEx concept study reports, with a multi-object spectrograph incorporating multiple grating modes at the core of the instrument, and a high-resolution echelle mode and UV imager also under study (collectively referred to as the HWO UltraViolet Instrument, UVI). Recently, the HWO project office has also initiated the study of a secondary integral-field spectrograph. Taken together, the HWO UV spectrographs require gratings of several types spanning from low-resolution, low-blaze-angle modes to the highest-resolution echelle types. It is necessary to develop advanced, aberration-correcting, high-efficiency, low-scatter diffraction gratings to support HWO’s need for a wide range of grating characteristics. These efforts leverage recent APRA and SAT programs that developed viable fabrication techniques for improving echelle gratings, realizing ultralow blaze angles, creating custom groove shapes on curved surfaces, and infusing these technologies into suborbital demonstration missions. The continuation of these studies will increase the performance and technology readiness level of UV gratings through improved fabrication processes and performance verification, thus directly addressing top-priority technology gaps. In addition, the gratings will be studied for incorporation into intermediate-scale missions for demonstration in a mission framework (e.g., class D) that exists between the suborbital and HWO level.
