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Reflective Spatial Heterodyne Spectrometers (RSHS): A high resolving power broadband spectral sensor for the EUV-NIR

Presentation #211.16 in the session We Know the Way: Future Missions, Instruments, Facilities (iPosters).

Published onOct 20, 2022
Reflective Spatial Heterodyne Spectrometers (RSHS): A high resolving power broadband spectral sensor for the EUV-NIR

Spectroscopic study of the intensity and distribution of discrete emission & absorption features over the Far Ultraviolet (FUV) to Near Infrared (NIR) range is an essential remote sensing technique for the study of a wide range of solar system targets comet comae & tails, planetary upper atmospheres & coronae, aurora, magnetospheric plasmas, and solar wind interactions. The intensity of these features provides useful information on column density, spatial distribution, and energy deposition rate. However, by probing the lineshapes of these emission features with high resolution spectroscopy (HRS) we are gain invaluable insight into the underlying processes giving rise to the observed emissions including non-thermal energtic processes, Joule heating, turbulence, atmospheric escape, multimodal populations, isotopic ratios, and optical depth. The current generation of spectrometers are able to measure intensity with high-precision but lack the resolving power to access Doppler structure in emission features.

In this presentation we describe the potential of broadband reflective spatial heterodyne spectrometer (RSHS) for spaceflight investigations where high-resolving power measurements of EUV-NIR emission features would enhance scientific return. RSHS is compact Fourier Transform Spectrometer (FTS) that samples a wide field of view (~0.5 degrees) at resolving powers >100000. In its basic form, a diffraction grating splits an incoming beam into symmetric orders that counter circulate through a set of pilot mirrors to form a 2-D interference pattern. A single alignment of the pilot mirrors samples a bandpass of ~1 nm. We recently developed a flight-ready design for a tunable RSHS that scan across bandpass from 115-185 nm by rotation of the pilot mirrors. The instrument is low mass & volume such that it can be used in SmallSat and larger spacecraft. The optical design is further flexible, such that a change in the grating allows the same instrument to be use for a variety of applications across the entire EUV-NIR range.

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