Monitoring Space Debris

We’re Making More and More Debris
The number of debris objects, their combined mass, and the total area they take up has been steadily increasing since the beginning of the space age. This is further fueled by a large number of in-orbit break-ups of spacecraft and rocket stages.

The total area that space debris takes up is important as it is directly related to how many collisions we expect in the future. As things stand, collisions between debris and working satellites is predicted to overtake explosions as the dominant source of debris.

Debris-Creating Events Have Become More Common
On average over the last two decades, 12 accidental ‘fragmentations’ have occurred in space every year – and this trend is unfortunately increasing. Fragmentation events describe moments in which debris is created due to collisions, explosions, electrical problems and even just the detachment of objects due to the harsh conditions in space.

On the bright side

Attempts Are Being Made to Follow the Rules (Not Yet Enough)
While not all satellites currently comply with international guidelines, more and more space actors are attempting to stick to the rules. In the last decade, 15-30 percent of objects, or ‘payloads’ launched into non-compliant orbits in the low-Earth orbit region (excluding spacecraft related to human spaceflight) had attempted to comply with debris mitigation measures. Between 5 percent and 20 percent did so successfully, peaking at 35 percent in 2018 due to the active de-orbiting from the Iridium constellation.

More Rockets Are Being Safely Disposed Of
When it comes to rockets, more and more are being sustainably disposed of. Between 40 and 80 percent of those in a non-compliant low-Earth orbit this decade attempted to comply with debris mitigation measures. Of these, 30-70 percent did so successfully.

Of all the rockets launched in the last decade, 60-80 percent (in terms of mass) adhered to mitigation measures. Some rockets are in low-Earth orbits that lead them to decay naturally in Earth’s atmosphere, but a significant amount of rockets are directed back into Earth’s atmosphere where they either burn up or are made to re-enter over uninhabited areas. Such practices are increasing, with about 30 percent of rockets safely re-entering in a controlled manner since 2017.

This is very good news. Rocket bodies are among the largest objects we send to space and are at a high risk of being involved in catastrophic collisions. All steps to ensure they do not linger in orbit after a maximum of 24 hours from launch is to be celebrated. 

More Satellites Put in Low-Altitude Orbits Where They Naturally Burn Up
The amount of ‘traffic’ launched into the low-Earth orbit protected region – up to 2000 km in altitude – is changing significantly, in particular due to the proliferation of small satellites and constellations.

Around 88 percent of small payloads launched into this region will naturally adhere to space debris mitigation measures due to their low altitude, meaning they break up in Earth’s atmosphere.

Between 30-60 percent of all satellite mass (excluding from human spaceflight) is estimated to adhere to end-of-life guidelines for the same reason. 

“The accelerating increase of satellites launched into low-Earth orbit is starkly visible in our latest report,” explains Tim Florer, Head of ESA’s Space Debris Office.

“We have observed fundamental changes in the way we are using space. To continue benefiting from the science, technology and data that operating in space brings, it is vital that we achieve better compliance with existing space debris mitigation guidelines in spacecraft design and operations. It cannot be stressed enough – this is essential for the sustainable use of space.”

High Rates of Debris Mitigation in Geostationary Orbit
Satellites launched into the geostationary protected region, 35 586 - 35 986 km in altitude, have very high rates of adherence to debris mitigation measures. Between 85 percent and 100 percent that reached the end of their life this decade attempted to comply with these measures, of which 60 - 90 percent did so successfully.

In geostationary orbit, there is a clear commercial interest for operators to keep their paths free from defunct satellites and debris – to not do so would put their spacecraft, and bottom line, at serious risk.

What now?

Systematic analysis of changing behaviors in space, when it comes to the adoption of debris mitigation measures, provides reasons to be cautiously optimistic – this was not the case a decade ago.

If adopted quickly, sustained investment in new technologies to passivate and dispose of missions will allow our environment to cope with the continued increase in space traffic and ever-more complex operations.

We must think of the space environment as a shared and limited natural resource. Continued creation of space debris will lead to the Kessler syndrome, when the density of objects in low Earth orbit is high enough that collisions between objects and debris create a cascade effect, each crash generating debris that then increases the likelihood of further collisions. At this point, certain orbits around Earth will become entirely inhospitable.

ESA notes that it is actively working to support the guidelines for the long-term sustainability of outer space activities from the UN Committee on the Peaceful Uses of Outer Space, including funding the world’s first mission to remove a piece of debris from orbit, helping to create an international space sustainability rating and developing technologies to automate collision avoidance and reduce the impact on our environment from space missions.

Find out more about ESA’s Space Debris and Clean Space Offices, both part of the Space Safety Program, and the Agency’s upcoming conference on space debris - the world’s largest on the topic - taking place in April 2021.