As the number of spacecraft circling Earth climbs at an unprecedented rate, concerns about satellite collisions are moving from theory to urgent reality.
Researchers at the University of Manchester have unveiled a new modelling approach that could reshape how Earth observation missions are planned, helping to safeguard crowded orbits while still delivering the data the world depends on.
John Mackintosh, lead author of the study and PhD researcher at The University of Manchester, said: “Our research addresses what is described as a ‘space sustainability paradox’, the risk that using satellites to solve environmental and social challenges on Earth could ultimately undermine the long-term sustainability of space itself.
“By integrating collision risk into early mission design, we ensure Earth-observation missions can be planned more responsibly, balancing data quality with the need to protect the orbital environment.”
A crowded orbit under pressure
Earth’s orbital environment is becoming increasingly congested. Around 11,800 active satellites are currently in space, and projections suggest that figure could exceed 100,000 before the end of the decade.
With more hardware comes a heightened risk of satellite collisions, which can generate clouds of space debris that linger for decades.
Each collision has the potential to produce thousands of fragments, threatening operational spacecraft, astronauts and critical orbital corridors. The stakes are high: once debris accumulates in certain regions, it can trigger a cascade of impacts that make those orbits unsafe to use.
At the same time, demand for space-based data is accelerating.
The essential role of Earth observation
Earth observation satellites play a central role in monitoring climate change, tracking land use, supporting food production and strengthening supply chains.
They are also key to disaster response and environmental protection, underpinning efforts aligned with the United Nations Sustainable Development Goals.
However, there is a growing tension between expanding satellite networks to meet global needs and maintaining a sustainable orbital environment. Using space to solve Earth’s problems could, if unmanaged, compromise the long-term usability of space itself.
The Manchester team set out to address this dilemma head-on.
Rethinking mission design from the start
Traditionally, satellite performance requirements and collision risk assessments have been handled separately, with risk considerations often introduced late in the development process. The new framework changes that order entirely.
Instead of treating collision risk as an afterthought, the model links mission objectives, such as image resolution and geographic coverage, with factors that influence the likelihood of satellite collisions.
These include spacecraft size and mass, the number of satellites in a constellation, orbital altitude and the concentration of debris in specific regions of low Earth orbit.
By bringing these elements together at the concept stage, mission planners can evaluate trade-offs early on. Designers can explore how altering altitude or adjusting image resolution might affect both data quality and exposure to debris.
Surprising insights about collision risk
One of the study’s key findings challenges common assumptions about satellite collisions. Risk does not simply peak where debris density is highest.
For example, when modelling a satellite capable of capturing imagery at 0.5-metre resolution, researchers found that collision probability was greatest between 850 and 950 kilometres above Earth’s surface. That zone sits roughly 50 kilometres higher than the area with the most concentrated debris.
Why the mismatch? Satellite size plays a critical role. Larger spacecraft present a bigger target and carry more energy in the event of an impact, increasing both the likelihood and consequences of a collision.
The research also highlights a trade-off between altitude and fleet size. Satellites operating at higher altitudes can cover wider areas, meaning fewer are needed. But those spacecraft must be larger and heavier to achieve high-resolution imaging, raising their individual collision risk.
In contrast, lower orbits require more satellites to maintain coverage, yet each unit can be smaller and less hazardous on its own.
Protecting space while serving Earth
By embedding collision analysis into mission design, the Manchester model offers a practical way to manage satellite collisions without compromising performance goals. It gives engineers a clearer view of how their technical choices influence long-term space sustainability.
The team believes the framework could be adapted to a range of Earth observation systems and refined to capture broader environmental impacts.
Future iterations may account for how long debris fragments remain in orbit, their probability of striking other spacecraft and even the environmental effects of satellite re-entry.
If widely adopted, this approach could help ensure that efforts to monitor climate change, safeguard food systems, and strengthen global resilience do not unintentionally fuel the very orbital congestion that threatens them.
