Multi-model ensembles for upper atmosphere modelling

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The neutral atmospheric density from 200 to 1000 km altitude can change by 80% diurnally as well as by one to two orders of magnitude during geomagnetic storms. The upper atmosphere forecast models currently in use can result in large uncertainties in the orbital parameters when applied to satellite orbit forecasts (i.e. positional errors on the order of kilometres after a day). The accuracy of such models (nowcast and forecast) is further limited by the lack of neutral atmosphere measurements at the appropriate altitudes. Without the capability to more accurately predict orbital trajectories, and thereby better plan satellite collision avoidance manoeuvres, orbital collisions could become frequent enough to cause a cascade, known as the Kessler Syndrome. This has the potential to prevent the use of low Earth orbit (LEO).The use of multi-model ensembles (MMEs) is emerging as a possible way to improve the performance of atmospheric density models and thereby improve orbital predictions. Initial MME work has demonstrated a significant reduction in the RMS errors of total neutral density (by approximately 60%). The proposed programme will aim to demonstrate the use of MMEs over wider range of conditions; formalise the construction of the MME; and expand the use to ionospheric as well as thermospheric densities. Work placements will be undertaken at Dstl and will be focused on testing the new models against data.