Space Weather Instrumentation, Measurement, Modelling and Risk: Thermosphere (SWIMMR-T)

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Space debris is emerging as a key problem 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. On average the United States Strategic Command issue ~900 Conjunction Data Messages (providing expected miss distance, estimated probability of collision, time of closest approach, and closest approach relative position and velocity) to users every day.The European Space Agency currently estimates that the economic loss to European satellite operators from collisions and unnecessary avoidance manoeuvres is in excess of £200 million per year. Moreover, with the number of objects (> 1 cm) increasing by ~70,000 per year, collisions will inevitably increase and if the debris reaches a critical density, an uncontrolled collision cascade known as the Kessler Syndrome is likely to occur. This has the potential to limit use of LEO and to increase concerns for the safety of all spaceflight. As such, there are two primary concerns: the sustainability of space activities over the longer-term, and the safety of spaceflight over the shorter-term. Therefore it is essential not only to reduce the number of debris objects in LEO, but also to improve the accuracy in predictions of near misses and to enable timely and efficient planning of collision avoidance manoeuvres. However, a major problem is that 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 of LEO objects is the density of the upper atmosphere (thermosphere), which exerts a time and location dependent drag. Given that the thermospheric density can vary by 80% diurnally and by 250% during a solar storm this is a major modelling challenge. Contemporary models used to forecast orbit trajectories are empirical and can result in large uncertainties corresponding to positional errors of kilometres after just one day. These inaccuracies result in unnecessary satellite avoidance manoeuvres at great cost to satellite operators.In order to better predict orbital conjunctions a fully coupled (neutral and ionized) model of the lower and upper atmosphere is required into which a broad range of measurement data can be assimilated using novel mathematical techniques. This approach will provide a complete and accurate picture of the ionosphere and thermosphere.Our programme seeks to secure a step-change in the Met Office's (and more broadly the UK's) ability to specify and forecast the thermosphere. To achieve our objectives, we will leverage background IP from previous NERC, EPSRC, UKSA, ESA and Dstl grants and contracts and explore new techniques. In the case of the leveraged IP we expect that all models will be at TRL 6 by the grant end and new research will be on a best efforts basis. We will achieve our objectives by benefitting from a four-institution consortium of some of the country's principal experts. The majority of the programme will focus on environmental models, but while doing this we will maintain an awareness of the applications for these models, satellite operators.