Small satellite operations planning for agile disaster response using graph theoretical techniques

Agile, manoeuvrable, satellite constellations have the potential to fundamentally change space mission design by moving away from traditional missions, designed to address predicted demand, and instead providing responsive systems that can react to real-time events, such as natural disasters. The unique advantages of responsive constellations are enhanced by the use of small satellites, whose short development times and low cost can offset the increased risk and shorter mission life inherent in the use of manoeuvrable spacecraft. In addition, newly developed, highly efficient propulsion systems can provide small satellites with agile manoeuvrability. This could enable agile satellite systems where efficient, low-thrust, responsive manoeuvres can be used to ensure rapid flyover of targets on Earth. The authors have previously developed a fully analytical method of designing such manoeuvres, which allows consideration of multiple targeting options, each with different flyover times, view angles, and propellant requirements. However, a long-term, holistic understanding of the concept of operations is required to effectively implement an agile satellite system. To facilitate this, the existing analytical methodology has been combined with graph theoretical techniques to allow the complex trade-space to be perceived as a graph. The connections in the graph represent possible manoeuvres and are rapidly traversed to identify favourable routes to achieve the desired goal. The effect of changes in mission priorities can be assessed by reweighting the graph, avoiding the need to recalculate the manoeuvre options. This work demonstrates that the proposed method can be successfully used to plan sequential flyovers of a moving target; in this case, a tropical storm. For the small spacecraft and low-thrust propulsion system considered, the possible changes in flyover time for each target are small, however, these small adjustments can be used to significantly improve the quality of the obtained data compared to a non-manoeuvring spacecraft.