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Errors From Asymmetric Emission Rate in Spaceborne, Limb Sounding Doppler Interferometry: A Correction Algorithm With
Yen-Jung J Wu1, Brian J Harding1, Colin C Triplett1
1Space Sciences Laboratory University of California Berkeley CA USA.
Earth and Space Science (Hoboken, N.J.)
|November 2, 2020
Summary
A new algorithm improves thermospheric wind measurements by accounting for uneven airglow, significantly reducing errors near solar terminators for the MIGHTI instrument on the ICON mission.
Area of Science:
- Space Physics
- Atmospheric Science
- Aeronomy
Background:
- The Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument on NASA's ICON mission measures thermospheric neutral wind and temperature.
- Existing wind retrieval algorithms assume constant airglow volume emission rates (VER), leading to significant uncertainties near solar terminators and equatorial arcs due to large VER gradients.
Purpose of the Study:
- To introduce and evaluate a new wind retrieval algorithm (Wu20) that accounts for asymmetric VER along the line of sight.
- To quantify the impact of the symmetric airglow assumption on ICON's vector wind product and assess the improvement offered by the Wu20 algorithm.
Main Methods:
- Developed the Wu20 algorithm to incorporate asymmetric VER, improving upon the constant VER assumption of the Harding17 algorithm.
- Utilized predicted ICON orbit data and simulated global VER variations to test the algorithm's performance.
Main Results:
- The symmetric airglow assumption introduces errors of at least 10 m/s in the ICON vector wind product within 30° of the terminator on the dayside.
- The new Wu20 algorithm reduces these terminator-region errors by a factor of 10.
- The Wu20 algorithm improves retrieval accuracy but decreases precision by 75% compared to the Harding17 algorithm.
Conclusions:
- The Wu20 algorithm significantly enhances the accuracy of thermospheric wind measurements derived from MIGHTI/ICON data, particularly in challenging regions near the solar terminator.
- Accounting for asymmetric airglow volume emission rates is crucial for precise thermospheric wind retrievals.
- Future work may focus on optimizing the Wu20 algorithm to balance accuracy improvements with precision recovery.
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