Determine the geometry of the HWO instrument bay for the integral-field spectrograph

Determine the geometry of the HWO instrument bay and, consequently, the permissible placement and optical accommodation of the ultraviolet integral-field spectrograph relative to the telescope focal plane and other instrument channels.

Background

The proposed ultraviolet integral-field spectrograph (IFS) is packaged within the same notional instrument bay as the multi-object spectrograph, imager, and high-resolution spectrograph. Its optical layout depends on where the telescope focal plane and surrounding structures are located within that bay.

Because the authors do not know the actual bay geometry, they adopt an assumption that the telescope focal plane is at the edge of the bay and that structures cannot extend beyond the microshutter array toward the final telescope fold mirror. The unresolved geometry directly affects the placement of the IFS image slicer, fold mirror, detectors, and associated optics.

References

We do not know the geometry of the instrument bay, therefore we assume that the telescope focal plane where the MSA is located is at the edge of the instrument bay, and that structures and optics cannot extend beyond the MSA in the direction of the final telescope fold mirror.

— An Ultraviolet Instrument on the Habitable Worlds Observatory: Considerations and Capability Trades on the Multi-Object, Integral-field, and High-resolution modes of a potential UVI  (2610.12974 - Fleming et al., 9 Oct 2026) in Section 3.4, subsection “A basic design for the IFS”

This could be as much as 150 to 350 mm, an amount that it is not clear is available in the EAC telescope designs.

— An Ultraviolet Instrument on the Habitable Worlds Observatory: Considerations and Capability Trades on the Multi-Object, Integral-field, and High-resolution modes of a potential UVI  (2610.12974 - Fleming et al., 9 Oct 2026) in Section 5.2.1, subsection “An Independent Optical Path”