SA43A-2358
First Performance Results of a New Geocoronal Balmer-alpha Field-Widened Spatial Heterodyne Spectrometer

Thursday, 17 December 2015
Poster Hall (Moscone South)
Derek Gardner1, Edwin J Mierkiewicz2, Fred L Roesler1, John Harlander3, Kurt Jaehnig1, Susan M Nossal4 and L. M. Haffner5, (1)University of Wisconsin Madison, Madison, WI, United States, (2)Embry-Riddle Aeronautical University, Daytona Beach, FL, United States, (3)Saint Cloud State University, St Cloud, MN, United States, (4)Univ Wisconsin Madison, Madison, WI, United States, (5)University of Wisconsin Madison, Astronomy, Madison, WI, United States
Abstract:
During 2013, a new, high resolution field-widened spatial heterodyne spectrometer (FW-SHS) uniquely designed to observe geocoronal Balmer-alpha emission ([Ha], 6563A) 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 (FPI) optimized for [Ha], also at PBO. The FW-SHS is a robust new Fourier-transform instrument that combines a large throughput advantage with high spectral resolution and a relatively long spectral baseline (~10x that of the FPI) in a compact, versatile instrument with no moving parts. Coincident [Ha] observations by FW-SHS and FPI were obtained over similar integration times, resolving power (~80,000 at [Ha]) and field-of-view (1.8 and 1.4 degrees, respectively). This paper describes the FW-SHS first light performance and [Ha] observational results collected from observing nights across 2013 and 2014.

Initial FW-SHS observations of Balmer-alpha 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 is capable of determining geocoronal Balmer-alpha doppler shifts on the order of 100 m/s across a 640km/s [Ha] spectral bandpass, with a temporal resolution on the order of minutes. These characteristics make the FW-SHS well suited for spectroscopic studies of relatively faint, diffuse-source geocoronal Balmer-alpha emission from Earth’s upper atmosphere (~2-14R) and the interstellar medium in our Galaxy. Current and future observations expand long-term geocoronal hydrogen observation data sets already spanning two solar maximums.