The move comes amid growing concern about the congestion and pollution of space, with debris levels continuing to rise despite ongoing mitigation efforts.
“The space environment health index is an elegant approach to link the global consequences of space debris mitigation practices to a quantifiable impact on the space debris environment,” said Stijn Lemmens, European Space Agency (ESA) space debris mitigation analyst.
Much like how global temperatures serve as an indicator of climate change, the health index provides a clear metric for assessing how sustainable the orbital environment is and how current missions will affect it over the next 200 years.
Lemmens added, “With this new metric, ESA is promoting a common language for assessing the impact of our space activities and making consequences concrete.”
The index distils a complex web of factors – from object size, lifetime in orbit and manoeuvring capability to the risk of fragmentation and explosion – into a single score.
A high score signals greater environmental stress, while a low score indicates more sustainable behaviour. In time, ESA hopes the measure could act much like an “energy-efficiency rating” for satellites, offering operators and regulators a benchmark for sustainability.
ESA’s initiative supports its broader “Zero Debris by 2030” goal, which aims to end debris generation from its missions entirely within the decade. The agency and European researchers have spent almost 10 years linking satellite traffic, operator behaviour and orbital dynamics to build the model underpinning the index.
According to ESA, the current global health index sits at level four times worse than the level deemed sustainable under international guidelines set by the Inter-Agency Space Debris Coordination Committee in 2014. Even then, forecasts suggested the environment was already three times riskier than ideal.
Francesca Letizia, ESA’s space debris mitigation engineer, said the health index has already proven useful in policymaking. “We used the health index model to translate the mandate for a zero debris approach into numbers, identifying a path that would not exceed the orbital sustainability threshold,” she said.
Beyond scientific modelling, the index is expected to play a growing role in space mission design, licensing, regulation and even insurance. It could guide mission planners to adopt safer designs, such as shorter orbital lifetimes, reliable deorbiting systems and effective collision avoidance.
ESA warned the challenge cannot be deferred. Each new object added to orbit increases long-term risk and fragmentation events today will shape conditions for decades. The index, the agency said, is a practical tool to ensure today’s decisions protect tomorrow’s access to space.