Global High-Altitude Oxygen (130.4nm and 135.6nm) Radiance Observations with the Carruthers Geocorona Observatory via Source Separation

The Carruthers Geocorona Observatory—scheduled to launch in September 2025—is NASA’s first mission devoted to investigating the fundamental nature of Earth’s exosphere from its distant vantage in halo orbit around the Earth-Sun L1 Lagrange point. Its primary payload, the GeoCoronal Imager, consists of two co aligned photometric imagers that measure ultraviolet Lyman-alpha emission radiance from exospheric hydrogen (H) simultaneously at wide- and narrow fields of view. These observations will map the exosphere’s global spatial structure and observe its temporal variability in response to geomagnetic storms. A critical step in that analysis is isolating the in band H Lyman alpha signal from out of band photon backgrounds, which are dominated by oxygen emissions at 130.4 nm and 135.6 nm at Earth's limb. Here, we introduce a source separation technique that retrieves global maps of high altitude (>500 km) Oxygen 130.4 nm and 135.6 nm radiances from daily observations of Earth's thermospheric FUV emissions. We validate this approach using synthetic images of an assumed FUV spectrum as observed with our instrument’s expected optical and spectral response.