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 (~10 times 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 and 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) versus 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 band pass 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 Earthˈs 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.
Journal of Geophysical Research: Space Physics
American Geophysical Union
Scholarly Commons Citation
Gardner, D. D., Mierkiewicz, E. J., Roesler, F. L., Harlander, J. M., Jaehnig, K. P., Nossal, S. M., & Haffner, L. M. (2017). First Performance Results of a New Field-Widened Spatial Heterodyne Spectrometer for Geocoronal Hα Research. Journal of Geophysical Research: Space Physics, 122(1). https://doi.org/10.1002/2016JA022625
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