Low Earth orbit is filling with both satellites and debris, yet collision risk is usually assessed late in mission design, after the key architectural choices are fixed. University of Manchester researchers, led by John Mackintosh, have developed a modelling framework that lets Earth-observation mission designers weigh collision risk and mission performance together from the outset, published in Advances in Space Research.
The framework connects imaging requirements such as resolution and coverage to the satellite size and mass needed to deliver them, the number of spacecraft a constellation requires, and the debris environment at different altitudes. Its most useful insight is that risk does not simply track debris density. Because satellite size matters as much as the local environment, a mission delivering half-metre resolution imagery faces peak collision probability between 850 and 950 kilometres altitude, about 50 kilometres above the peak in debris concentration.
The analysis exposes a structural trade-off in constellation design: higher orbits need fewer but larger satellites, each carrying greater individual collision risk, while lower orbits demand more numerous, smaller and individually less hazardous spacecraft. By quantifying that balance early in the design process, the tool could help operators build constellations that are both commercially efficient and responsible tenants of an increasingly congested orbital commons.