Space weather risk modelling

Space debris is emerging as a key problem for humanity with the potential to cause major socio-economic impacts. It is currently estimated that there are over 900,000 pieces of debris greater than 1 cm orbiting the Earth. Collisions with such objects can destroy satellite instruments, subsystems and even the satellite itself. It has been estimated that the economic loss to European satellite operators from collisions and unnecessary avoidance manoeuvres is in excess of £200 million per year.

Current orbit modelling and prediction is insufficiently accurate because of the time-varying drag effect of the upper atmosphere on satellites. The dominant unknown in orbital trajectory predictions is the density of the upper atmosphere (thermosphere), which exerts a time and location dependent drag.

SWIMMR-T will combine state-of-the-art atmospheric models to generate accurate and actionable nowcasts and forecasts of the thermosphere which in turn will be used to produce reduced uncertainty estimates of the orbital characteristics of satellites and debris.

The SWIMMR-T project is led by a modelling team at the University of Birmingham using the near-real-time (NRT) Advanced Ensemble electron density (Ne) Assimilation System (AENeAS). BAS will be working with the University of Lancaster to integrate state-of-the-art models of the ionospheric electric field, empirically determined from data from the international SuperDARN radar network.

The SWIMMR-T programme seeks to secure a step-change in the UK’s ability to specify and forecast the thermosphere. SWIMMR-T has the following specific objectives.

• Objective 1 – Enhance and operationalise AENeAS for thermospheric forecasting. This will bridge a gap in the UKs space environment modelling capability enabling near real-time nowcasting, and forecasting, of the thermosphere.
• Objective 2 – Perform a rigorous comparison of state-of-the-art high latitude electric field models, implement both spherical harmonic and gridded model output into AENeAS and quantify its impact on nowcasting and forecasting the thermosphere.
• Objective 3 – Using the enhanced version of AENeAS, and previously developed orbit propagators, determine to what extent Joule heating and radiative cooling of the thermosphere affects orbiting satellites.
• Objective 4 – Quantify the long-term impact of radiative cooling of the thermosphere, associated with increased CO2 levels, on the space debris population.

The BAS SWIMMR-T team will be responsible for delivering Objective 2 of the project, in collaboration with the University of Lancaster.