Space environment health index – 2025

The ESA space environment health index quantifies how our behaviour now impacts the orbital environment in the future. The model behind it can also be used to establish the impact of a particular mission on the environment over time.

Each year with a value in the diagram reflects the effect of all objects in space at that time combined on the space environment projected over a period of 200 years.

The red extrapolation is a forecast of what happens if there is no change in behaviour, black what happens with only the current objects in space, and green indicates the orbital sustainability threshold.

The orbital threshold (green dotted line) is the highest desirable value, which is to say that this would already not be ideal, but would pose potentially manageable levels of risk to the Earth’s space environment and the missions flying in it.   

Read the full ESA Space Environment Report for a detailed explanation of the calculations and reasoning.
 
In the diagram here you can see that anything over 1 (= the orbital sustainability threshold, or the maximum that is desirable as based on IADC guidelines from before the boom in large constellations) is not deemed sustainable in the long run.

We are now at a health index value of 4 if we continue our current behaviour, far beyond the sustainability threshold. This despite an increase in awareness of space debris mitigation guidelines and a growing willingness to tackle the problem.

Even stronger action is required to protect our future in space.