Thermosphere Observations from Low-Earth Orbiting Satellites

Abstract

The thermosphere observations from low-Earth orbiting satellites (TOLEOS) project will provide new thermosphere density and crosswind observations derived from the accelerometer data of the CHAMP, GRACE, and GRACE-FO missions. These new data products will cover the entirety of the accelerometer missions and complement the existing ESA databases for Swarm and GOCE. The accurate calibration of the accelerometer data and the upgrade of the radiation pressure model are key elements of the project, which is funded by the Swarm Data, Innovation, and Science Cluster (Swarm DISC). For the calibration of GRACE accelerometer data, we pay special attention to thermally induced bias variations, which would degrade the results if not properly modelled. To improve the radiation pressure modelling, we use ray tracing techniques in combination with high-fidelity geometry models of the satellites, which were augmented with the thermo-optical properties of the surfaces. This substantially reduces the uncertainty stemming from the satellite geometry modelling and shadowing effects. In addition, we introduce thermal emission models of the satellites to account for the radiation of heat from the satellites themselves. Substantial validation activities are performed since the project’s start in June 2021 and will continue until the end of the project in July 2022. In this presentation, we will provide an overview of the results from the project. This will include a brief explanation of the accelerometer data calibration and the upgraded radiation pressure modelling, as well as selected results from the extensive validation activities. The main focus will be on the new thermosphere density and crosswind observations and how they compare to the existing observations to demonstrate the effects of the upgraded processing.