Title: "Airborne Infrared Remote Sensing Observations of the Solar Corona and Terrestrial Atmosphere"
Abstract: Airborne infrared imaging spectroscopy is a powerful tool for exploring both the solar corona and the terrestrial atmosphere. This talk presents recent results from the airborne infrared spectrometer (AIR‑Spec), which observed the corona during the 2017 and 2019 total solar eclipses, and reports on the ongoing validation flights of MethaneAIR, a new instrument that will make precise measurements of atmospheric methane.
AIR-Spec is a grating spectrometer that measures light over a 1.55 solar radius field of view in three spectral passbands between 1.4 and 3 μm. It was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from the NSF Gulfstream V research jet. These magnetically sensitive emission lines of highly ionized magnesium, silicon, sulfur, and iron are promising candidates for future observations of the coronal magnetic field, and their characterization is an important first step toward developing the next generation of instrumentation for coronal magnetometry. The second AIR-Spec research flight took place during the 2019 total solar eclipse across the south Pacific. Higher sensitivity and reduced jitter enabled more precise measurements of emission line properties and plasma density, temperature, and line-of-sight velocity up to one solar radius from the solar limb. Atmospheric absorption was significant, even at altitude, and atmospheric modeling will be required to extract accurate line intensities. The successful eclipse missions overcame a number of engineering challenges, centered around maintaining adequate resolution and signal-to-noise ratio in a compact and inexpensive package on a moving platform.
The development and testing of AIR-Spec provided valuable experience that accelerated the preparation of MethaneAIR, a pair of grating spectrometers that are currently undergoing their first flight tests on the Gulfstream V. MethaneAIR measures total-column dry air mole fraction of methane and carbon dioxide at high spatial resolution (6×7 m pixel size) and with high precision (0.1% at 0.4 km resolution) using the 1.27 μm oxygen singlet delta band and the 1.6 μm methane/carbon dioxide band. The fast turnaround provides ample time for the development of retrieval algorithms for MethaneSAT, on orbit 2022. In addition to serving as an airborne simulator for MethaneSAT, MethaneAIR is by itself a powerful tool for studies of methane, carbon dioxide, and stratospheric/mesospheric airglow.