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A New Data Set of Thermospheric Molecular Oxygen From the Global‐scale Observations of the Limb and Disk (GOLD) Mission
Author(s) -
Lumpe J. D.,
McClintock W. E.,
Evans J. S.,
Correira J.,
Veibell V.,
Beland S.,
Eastes R.
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja027812
Subject(s) - occultation , radio occultation , thermosphere , longitude , geostationary orbit , remote sensing , daytime , ionosphere , latitude , environmental science , altitude (triangle) , satellite , scale (ratio) , geodesy , meteorology , geology , atmospheric sciences , physics , astronomy , geophysics , mathematics , geometry , quantum mechanics
The Global‐scale Observations of the Limb and Disk (GOLD) instrument was launched on 25 January 2018 onboard the SES‐14 commercial communications satellite and began nominal science operations in October 2018. Operating from geostationary orbit at 47.5°W longitude, GOLD images the Earth's thermosphere and ionosphere in the far‐ultraviolet (132–162 nm), measuring critical geophysical parameters by continuously scanning the Earth's disk and limb 18 hours per day. GOLD also performs stellar occultation measurements using bright type O and B stars. Up to 10 occultations per day are obtained at latitudes ranging from 60°S to 45°N and two fixed longitudes, ~33°E and ~128°W. The occultation data provide a direct measurement of atmospheric absorption in the O 2 Schumann Runge continuum, which is used to retrieve the O 2 density profile from 130‐ to 200‐km altitude. This paper describes the GOLD occultation measurement technique and the operational retrieval algorithm used to derive the Level 2 O2DEN data product. The spatial, temporal, and local time sampling of the GOLD O 2 data product is summarized, and the data quality, retrieval errors, and validation plans are discussed. Occultations are observed under both daytime and nighttime conditions, providing the O 2 density over a complete range of local times. GOLD retrievals have an estimated precision of 10% and a vertical resolution of 5–10 km, depending on altitude. The data have sufficient accuracy and resolution to provide scientifically useful constraints on the O 2 abundance and variability. Initial comparisons show qualitative agreement, but also notable differences, between the GOLD O 2 data and the Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar (NRLMSISE‐00) empirical model predictions.