\tSpace Safety<\/p>\n
\t\t\t\t\t\t22\/10\/2025
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The congestion and pollution of Earth orbit is quickly getting worse. We need to be able to quantify how our behaviour impacts the orbital environment in the future. To this end, the European Space Agency (ESA) is adding a new health index to its yearly Space Environment Report<\/a> that summarises in one number the status of our space environment over time.<\/p>\n \t\t\t\t\t\t\tModel of the distribution of space debris around Earth<\/a><\/p>\n \u201cThe 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,\u201d says Stijn Lemmens, space debris mitigation analyst at ESA.<\/p>\n \u201cWith the new metric, ESA is promoting a common language for assessing the impact of our space activities and making consequences concrete.\u201d<\/p>\n \tThe need for a yardstick<\/p>\n To keep our space environment safe and sustainable, we need a way to measure its overall health and quantify the impact each new mission will have.<\/p>\n Just as climate scientists use temperature as a key indicator of global warming, the space community needs a clear, quantifiable metric to assess the impact of objects and missions on orbital sustainability.<\/p>\n The Space Environment Health Index provides such a metric. It is a single score that reflects how healthy or stressed the orbital environment is and what the consequences will be in a 200-year time period.<\/p>\n \t\t\t\t\t\t\tImpression of the distribution of space debris around Earth<\/a><\/p>\n Even if one number can never explain all the intricacies involved, it will provide a useful impression of the space environment\u2019s health that speeds up high-level conversations. Also, it will provide a framework to evaluate individual missions on how they will impact the overall state.<\/p>\n The Health Index supports global sustainability efforts, including ESA\u2019s own Zero Debris approach<\/a>, which aims to eliminate debris generation from ESA missions by 2030.<\/p>\n \tIngredients of the new metric<\/p>\n For nearly 10 years, ESA and European academia have been working on understanding the links between space traffic, operator behaviour and orbital dynamics as a combined system. The Space Environment Health Index is designed to distil complex factors into one understandable score.<\/p>\n Each object or new mission has certain qualities that can be converted into a positive or a negative effect on the Index, such as:<\/p>\n Size: How big is it and what shape does it have?<\/p>\n Lifetime in orbit: How soon will the object naturally re-enter or be removed?<\/p>\n Collision avoidance capability: Can the object manoeuvre to prevent collisions?<\/p>\n Passivation measures: Has the object been made safe from explosions after its mission ends?<\/p>\n Fragmentation risk: What is the likelihood of the object breaking apart and creating debris?<\/p>\n \t\t\t\t\t\t\tCumulative number of collisions in low-Earth orbit if we continue as is<\/a><\/p>\n By combining these elements, it captures the risks of a mission\u2019s potential to create space debris, how that debris will increase collision risk for one’s neighbours, and how it will statistically have impacted the space environment after 200 years (see the full ESA Space Environment Report<\/a> for calculation details).<\/p>\n \nA high score indicates a greater negative impact on the environment, while a low score reflects more sustainable behaviour. It can then work like an energy-efficiency rating for appliances: in the future, a mission could be rated \u201cA\u201d for sustainability, giving operators and regulators a clear benchmark. \tOur current score: the alarm is sounding <\/p>\n \t\t\t\t\t\t\tThe diagram displays the Health Index forecasting the sustainability of our activities in Earth’s space environment into the future<\/a><\/p>\n The Space Environment Health Index measures how sustainable Earth\u2019s orbital environment is. A value of 1 represents the proposed threshold for long-term sustainability. Anything higher means that the space environment becomes less then desirable for operations over time and could eventually become unstable.<\/p>\n This benchmark of the Health Index is based on the Inter-Agency Space Debris Coordination Committee (IADC)<\/a> guidelines as in 2014, before the boom in large constellations. These guidelines outlined what a \u2018healthy\u2019 space environment should have looked like in 200 years, assuming space operators follow space debris mitigation<\/a> rules as established then.<\/p>\n Even back in 2014, the forecast was not ideal. The expected future was already three times riskier than the minimum deemed desirable. Today, with more satellites and more debris, the risk has climbed to four times higher. Despite many satellite operators already adopting space debris mitigation practices, more action is needed.<\/p>\n We are now at Health Index level 4, far beyond the sustainability threshold. Stronger action is required to protect our future in space.\u00a0 \u00a0<\/p>\n \tPotential uses of the Health Index<\/p>\n The index is more than a scientific tool \u2013 it is a practical decision-making aid. It can be applied to mission design to minimise its environmental impact, similar to other life cycle assessment tools and practices. A low score becomes a design target, encouraging choices like shorter orbital lifetimes, reliable deorbiting systems and strong collision avoidance capabilities.<\/p>\n \u201cEven if the definition of the Health Index may seem very theoretical, at ESA we have already successfully applied this concept in practice,\u201d explains Francesca Letizia, space debris mitigation engineer at ESA.<\/p>\n
All objects\u2019 scores together result in a global Health Index that indicates the overall state of the orbital environment compared to a reference baseline.<\/p>\n