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An Airborne Coronal Emission Surveyor (ACES) for Total Solar Eclipse Observations

Presentation #303.06 in the session Solar and Atmospheric Science with Eclipses.

Published onOct 20, 2022
An Airborne Coronal Emission Surveyor (ACES) for Total Solar Eclipse Observations

The Airborne Coronal Emission Surveyor (ACES) is a new imaging Fourier transform spectrometer that will explore the large-scale coronal infrared (IR) emission spectrum during the April 8, 2024 total solar eclipse. ACES will fly along the path of totality on the NSF/NCAR Gulfstream V High-performance Instrumented Airborne Platform for Environmental Research (GV HIAPER), with a stabilized solar feed provided by the Airborne Stabilized Platform for InfraRed Experiments (ASPIRE). During the 6-minute total eclipse, ACES will map emission line intensity in the 1–4 micron wavelength region at over a 2 Rsun × 100 arcsec field of view. A GV altitude of at least 13 km will enable it to survey the near and mid-IR with minimal atmospheric interference.

ACES is the latest in a line of NSF-funded airborne instruments developed to explore the IR emission corona from GV HIAPER. Previous instruments include the Airborne InfraRed Spectrometer (AIR-Spec), a cryogenic grating spectrometer that observed the 2017 and 2019 eclipses, and ASPIRE, which improves on the AIR-Spec image stabilization system to provide a 20 cm solar feed stabilized to 5 arcsec RMS over 1 second. Unlike AIR-Spec, which observed in four narrow spectral windows, ACES will survey the entire 1–4 micron (2,500–10,000 cm-1) spectral range at high (0.2 cm-1) spectral resolution.

ACES is expected to observe neutral helium as well as 18 forbidden lines of ionized magnesium, silicon, sulfur, argon, calcium, and iron, half of which have never been measured before. It may also observe weaker lines of those and other ions. The mission addresses science questions related to the strength of different emission lines in different regions of the corona, the relative radiative to collisional excitation in each line, the best temperature and density diagnostics in the passband, and the variation of elemental abundances across the corona. The instrument consists of a condenser telescope, cryogenic Michelson interferometer, achromatic lens, and IR camera. The 2024 eclipse flight will serve as the ACES commissioning flight.

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