New Observations of the IR Emission Corona from the 2019 July 2 Eclipse Flight of the Airborne Infrared Spectrometer

The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from a Gulfstream V research jet owned by the National Science Foundation and operated by the National Center for Atmospheric Research. The second AIR-Spec research flight took place during the 2019 July 2 total solar eclipse across the south Pacific. The 2019 eclipse flight resulted in seven minutes of observations, during which the instrument measured all four of its target emission lines: S xi 1.393 mu m, Si x 1.431 mu m, S xi 1.921 mu m, and Fe ix 2.853 mu m. The 1.393 mu m S xi line was detected for the first time, and probable first detections were made of Si xi 1.934 mu m and Fe x 1.947 mu m. The 2017 AIR-Spec detection of Fe ix was confirmed and the first observations were made of the Fe ix line intensity as a function of solar radius. Telluric absorption features were used to calibrate the wavelength mapping, instrumental broadening, and throughput of the instrument. AIR-Spec underwent significant upgrades in preparation for the 2019 eclipse observation. The thermal background was reduced by a factor of 30, providing a 5.5x improvement in signal-to-noise ratio, and the postprocessed pointing stability was improved by a factor of 5 to <10 '' rms. In addition, two imaging artifacts were identified and resolved, improving the spectral resolution and making the 2019 data easier to interpret.