Characterization of a Tunable All-Reflective Spatial Heterodyne Spectrometer

Abstract

We present the characterization of a prototype Tunable All-Reflective Spatial Heterodyne Spectrometer (TARSHS), a novel extension of the already-existing and successfully flight-demonstrated All-Reflective Spatial Heterodyne Spectrometer (ARSHS) design. ARSHS is recognized for its high resolving power (R > 105), wide field of view (FOV), and unique optical design that is especially well-suited for UV-visible remote sensing of faint and extended planetary and astrophysical targets. However, ARSHS utility is limited by a fixed and narrow bandpass. TARSHS overcomes this limitation by incorporating motor-driven rotation stages into the instrument pilot mirrors, enabling rapid selection between many different bandpass centers across a broad spectral range. This tunability significantly enhances the instrument’s versatility and potential science return per flight without sacrificing the high R and FOV that are characteristic of base ARSHS design. The TARSHS prototype reported below, assembled primarily with commercial-grade components, demonstrated a resolving power of R = 30,000 across an operable range of 400 – 700 nm. Stable, reliable tuning and minimal degradation across its tunable range were found, supporting its readiness for higher technology readiness levels (TRL). This study outlines the optical configuration, operational mechanics, and prototype results, establishing TARSHS as a robust, cost-effective tool for space-based spectroscopy. Future efforts should focus on miniaturization and environmental validation for deployment on robotic missions.