The Paradox Made Measurable - Manchester's New Design Tool Forces Collision Risk Estimation into the Earliest Stages of Mission Design

There's a tension at the heart of Earth Observation (EO) that the space sector has been slow to confront openly. Back in early 2022 the Satellite Applications Catapult aimed to convene a Net Zero Coalition and we jumped on this.  At the time a small group of us felt as if the space sector was yet to embrace emissions reporting of its own activities. The overwhelming consensus in the room was however to remain behind the camera, or sensor as it is from space, and focus on earth observation insofar as how it can shine a light on terrestrial harms.

Right now, the same EO satellites we rely upon to track deforestation and verify carbon credits and natural capital, map commodities abundance and humanitarian crises, and monitor climate change and coastal erosion are themselves contributing to an increasingly congested and hazardous orbital environment.

It is a difficult truth that the academic literature in 2023 labelled the space sustainability paradox.  Until now, the space community has had limited means of addressing it at the earliest stages of mission design.

New research from the University of Manchester's Space Systems Engineering Research Group, published in Advances in Space Research, presents a methodology that does exactly this. The work, led by PhD researcher John Mackintosh alongside Dr Ciara McGrath and Professor Katharine Smith, proposes a design tool that allows satellite mission planners to assess collision risk and debris generation potential concurrently with the performance requirements of the mission itself.

The core principle of assessment is straightforward. If you need 0.5m resolution imagery to support UN Sustainable Development Goal indicators, the altitude you choose does not just affect your data quality. Altitude in fact determines your satellite's size, its cross-sectional area, and therefore its probability of colliding with existing debris.

At higher altitudes, the optic payloads need to be larger, the satellite heavier, and the debris environment happens to be less forgiving.

The research demonstrates that for a satellite designed to that 0.5m benchmark, collision probability peaks between 850 and 950 km, roughly 50km higher than where debris flux itself peaks. The fragmentation potential climbs higher still, to around 1000 km, where both the probability of collision and the mass of the spacecraft compound to produce the worst-case debris generation event.

For constellations designed to a terrestrial coverage requirement like Copernicus Sentinel-2, the picture becomes a bit more nuanced. It is after all inherently helpful to capture more data in a single satellite overpass than to knit together multiple narrower strips into an image mosaic.

Fewer satellites are needed at higher altitudes, but each carries a substantially greater individual collision risk. A greater number of satellites at lower altitudes are individually smaller and less hazardous.

This is a trade-off that mission designers may have already contemplated, but until this work, lacked a quantitative framework to evaluate systematically during early design phases, instead reverting to a post design collision-risk acceptability thresholding.

What makes this particularly relevant for the sustainability community is the model explicitly works within the sustainability from space and sustainability in space lenses set out in the space sustainability paradox literature.

It describes how EO data is in many cases, the sole source of truth for measuring or estimating SDG indicators, and in parallel seeks to quantify the orbital cost of obtaining that knowledge. This becomes a critical step for careful EO mission design with greater acknowledgement of the debris-focussed environmental trade-offs being made.

From the perspective of Indexing organisational disclosures to rank and generate the Space Leaderboard, this kind of research sits firmly at the intersection of know and disclose and support and research. Manchester's Space Systems Engineering Research Group, ranked 17th on the current UK Space Leaderboard, continues to produce work that directly advances the sector's capacity for informed decision-making.

Their earlier work on Sustainability Challenges of the Space Industry and the Role of Life Cycle Assessment reporting has given rise to new Space Leaderboard methodological considerations, and this latest publication builds on that foundation by giving mission designers a bolthole to develop up-front, practical and quantitative assessments that can be used to defend sustainability-focussed outcomes with colleagues and investors.

The authors of course acknowledge the model limitations, including spherical satellites unlike those of the real world, and the toolkit is yet account for the collision probability during commissioning and decommissioning phases.  There is also the need to consider different environmental harms including ozone depletion from satellite re-entry and ablation.

The authors look toward future work incorporating full life cycle assessment, including terrestrial environmental and social impact, which would give an holistic picture. 

In all, these are small but very important steps, each one in a straight line to the intended destination of a lowest overall harm space environment.

 The University of Manchester press release is available.

The full open-access paper Collision risk from performance requirements in Earth observation mission design is available in Advances in Space Research.

https://doi.org/10.1016/j.asr.2026.01.019

#SpaceSustainability #EarthObservation #SpaceDebris #SDGs #CollisionRisk #MissionDesign #SpaceLeaderboard

*Graphic Design: Victoria Beall