Vertical Neutral Density (O+N2) Profiles From PROBA2/LYRA Observations

Satellite drag is the leading error source in predicting the locations of low-Earth orbit (LEO) satellites. Understanding the distribution and variability of thermospheric neutral densities is crucial for satellite tracking and operation. Historically, thermospheric neutral densities are usually derived from space-borne mass spectrometer and accelerometer measurements. In recent years, the Large Yield Radiometer (LYRA) instrument on board Project for Onboard Autonomy 2 (PROBA2) utilizes the solar occultation measurements and provides the vertical profiles of neutral (O+N₂) number density between 150 and 400 km altitudes. Data analysis has been carried out using this dataset during 2011-2017. Differences between the dawn and dusk density profiles have been investigated. Meanwhile, solar activity dependence of the neutral (O+N₂) density at different altitudes has been examined. The comparison between LYRA observations and MSIS empirical model has been conducted as well.