Tunable, all-reflective spatial heterodyne spectrometer for broadband spectral line studies in the visible and near-ultraviolet

A spatial heterodyne spectrometer (SHS) is an interferometric device that combines high resolving power and a large input acceptance angle in a compact format suitable for use at small telescope focal planes and spacecraft for observations of faint, angularly extended emission-line sources. The primary limitation of SHS instruments has come from the spatial sampling of their output interference pattern image, which limits their use to a narrow bandpass. We describe the first-light results from a broadband all-reflective SHS that can be mechanically aligned to any heterodyne wavelength from 300 to $700\mathrm{nm}$. Such an instrument can be extremely useful for the near simultaneous study of the brightness and line shapes of major atomic and molecular diagnostic emissions from extended astrophysical targets such as comets or planetary atmospheres. We discuss the results of this validation program and the potential improvements that could be used to expand and/or improve the broadband spectral response of the instrument.