Publication Date:
2016-11-18
Description:
A new, high resolution field-widened spatial heterodyne spectrometer (FW-SHS) designed to observe geocoronal Balmer α (Hα, 6563 Å) emission was installed at Pine Bluff Observatory (PBO) near Madison, Wisconsin. FW-SHS observations were compared with an already well-characterized dual-etalon Fabry-Perot Interferometer (PBO FPI) optimized for Hα, also at PBO. The FW-SHS is a robust Fourier transform instrument that combines a large throughput advantage with high spectral resolution and a relatively long spectral baseline (~10x that of the PBO FPI) in a compact, versatile instrument with no moving parts. Coincident Hα observations by FW-SHS and PBO FPI were obtained over similar integration times, resolving powers (~67,000 & 80,000 at Hα) and fields-of-view (1.8° and 1.4°, respectively). First light FW-SHS observations of Hα intensity and temperature (Doppler width) vs. viewing geometry (shadow altitude) show excellent relative agreement with the geocoronal observations previously obtained at PBO by FPI. The FW-SHS has a 640 km/s (14 Å) spectral bandpass, and is capable of determining geocoronal Hα Doppler shifts on the order of 100 m/s with a temporal resolution on the order of minutes. These characteristics make the FW-SHS well suited for spectroscopic studies of relatively faint (~12-2 R), diffuse-source geocoronal Hα emission from Earth's upper thermosphere and exosphere and the interstellar medium in our Galaxy. Current and future FW-SHS observations extend long-term geocoronal hydrogen observation data sets already spanning three solar minima. This paper describes the FW-SHS first light performance and Hα observational results collected from observing nights across 2013 and 2014.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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