Debris and non-functioning launcher steps in the geostationary ring. Aging satellites emit debris and explode due to residual energy sources. The resulting fragments can be thrown back and cross geostationary orbit. For this reason, the release of residual energy after the completion of the nominal mission is fundamental. ESA / ID & Sense / ONiRiXEL, CC BY-SA 3.0 IGO
Fragments of past space efforts are trapped in orbit around the Earth, threatening our future in space. Over time, the number, mass, and area of these debris objects gradually increase, which increases the performance of the satellites.
The ESA’s Office of Space Debris constantly monitors the condition of these ever-evolving debris and publishes a current report each year. The condition of the debris atmosphere.
Since the beginning of the space age in 1957, tons of rockets, spaceships and equipment have been launched into space. Initially, they had no plan of what to do with them at the end of their lives. Since then, the numbers have continued to rise and millions of dangerous debris have formed from explosions and collisions in space.
Despite advances in technology, the need to significantly increase the speed of understanding the space environment and implementing the proposed measures to reduce debris creation was recognized at the largest space debris conference ever held in Europe. Credit: ESA, CC BY-SA 3.0 IGO
“Explosions in orbit, the largest contributor to the current space debris problem, are caused by residual energy – fuel and batteries – onboard spacecraft and rockets. Despite years of efforts to prevent this, the number of such incidents has not decreased. Trends toward end-of-mission disposal are improving, but slowly, ”Said Holger Craig, head of the Space Safety Program.
“In view of the constant increase in space-traffic, we must develop and provide technology to prevent debris mitigation efforts, and the ESA is doing so through its space safety program. In parallel, regulators need to monitor the status of space systems, as well as the global commitment to debris mitigation within their jurisdiction.
International guidelines and standards now exist, which clarify how we can achieve sustainable use of space:
- Build rockets and spacecraft to reduce the amount of ‘shedding’ – the material is separated during launch and operation, due to the harsh conditions of space
- Avoid explosions by releasing stored energy, the ‘passivating’ spaceship once in a lifetime
- Move useless missions into the path of working satellites – by placing them in de-orbit or by moving them to ‘graveyard orbit’.
- Avoid space hazards by carefully selecting orbits and performing ‘collision avoidance stunts’.
Many space agencies, private companies and other space actors are changing their behavior to adhere to these guidelines – but is it enough?
Worrying trends
The objects we send into orbit take up the same space as the debris they create. The growing area of objects in space dramatically increases the probability of a collision. Red (PL) = payload; Orange (RB) = rocket body; Dark green (RM) = rocket mission related object. Credit: ESA
The number of debris objects, their composite mass and the total area they take up have been steadily increasing since the beginning of the space age. This is further fueled by the fact that a large number of spacecraft and rocket phases break down into orbit.
The total area taken up by space debris is important because it is directly related to how many collisions we have in the future. As things stand, collisions between debris and working satellites are thought to outweigh explosions as a major source of debris.
There are many ways to create debris in space. Thousands of hazardous debris can be added to Earth’s orbit for each “fragmentation event”. Credit: ESA
Incidents that create debris have become commonplace
On average over the past two decades, 12 accidental ‘fragmentations’ have occurred in space each year – and this trend is unfortunately on the rise. Fragmentation events describe the moments when debris is created by collisions, explosions, electrical problems, and the separation of objects due to harsh conditions in space.
The bright side
More satellites or “payloads” sent into low Earth orbit are trying to adhere more consistently to debris mitigation than 20 years ago. However, progress is still very slow. Credit: ESA
Attempts to follow the rules (not yet matched)
Although not all satellites currently comply with international guidelines, most space actors are trying to comply with the regulations. Over the past decade, 15-30% of objects, or ‘payloads’ launched into non-compliant orbits in low-Earth orbit (excluding spacecraft for human spaceflight) have attempted to comply with debris mitigation measures. It was successful between 5% and 20%, reaching 35% in 2018 due to being in active orbit from the Iridium Alliance.
80% of rockets launched now attempt to clear low-Earth orbit – most of which successfully – more than just 20% at the turn of the millennium. Credit: ESA
More rockets are being safely disposed of
When it comes to rockets, most are consistently disposed of. Between 40 and 80% of those in non-compliant low-Earth orbit during this decade have attempted to comply with debris mitigation measures. Overall, it successfully cleared 30-70% of low-Earth orbit in naturally non-compliant rockets.
Of all the rockets launched in the last decade, 60-80% (in terms of mass) are committed to mitigation measures. Some rockets are in low-Earth orbit, which causes them to naturally decline in the Earth’s atmosphere, but a significant amount of rockets are redirected back into the Earth’s atmosphere, where they burn up or re-enter uninhabited areas. Such practices are on the rise, with 30% of rockets safely entering re-controlled mode from 2017 onwards.
This is very good news. Rocket bodies are one of the biggest objects we send into space and are at risk of getting caught in catastrophic collisions. A maximum of 24 hours after the launch, all measures must be taken to ensure that they are not delayed in orbit.
Due to the increase in satellite constellations, the number of small satellites entering near-Earth orbit has increased dramatically in the last 10 years. Credit: ESA
Most satellites are in low altitude orbit, where they burn naturally
The amount of ‘small traffic’ into the low Earth orbit protected area – at an altitude of 2000 km – is changing significantly, especially due to the proliferation of smaller satellites and constellations.
Approximately 88% of the small payloads introduced in this region naturally adhere to space debris reduction measures because they are at low altitudes, i.e. they decompose in the Earth’s atmosphere.
It is estimated that between 30-60% of the total satellite mass (excluding human spaceflight) will adhere to life-end guidelines for the same reason.
“The rapid growth of satellites launched into low-Earth orbit is evident in our latest report,” explained Tim Florer, head of the ESA’s space debris office.
“We have observed fundamental changes in the way space is used. In order to continue to benefit from the science, technology and data that work in space, it is essential to achieve better compliance with existing space debris mitigation guidelines in spacecraft design and operations. This cannot be stressed enough – it is essential for the sustainable use of space. ”
In recent years, all satellites in geostationary orbit have attempted to exit responsibly after reaching the end of their mission. Credit: ESA
High rates of debris reduction in geostationary orbit
Satellites launched into geostationary protection, at an altitude of 35,586 – 35,986 km, are much more likely to adhere to debris mitigation measures. Between 85% and 100% of those approaching the end of their lives this decade have tried to conform to these measures, of which 60 – 90% have been successful.
In geostationary orbit, operators have a clear commercial interest in keeping their routes away from useless satellites and debris – otherwise their spacecraft and bottom line could be in serious danger.
What now?
A systematic analysis of changing behaviors in space provides reasons to be cautiously optimistic when adopting debris mitigation measures – something that did not happen a decade ago.
If adapted quickly, continuous investment in new technologies to deactivate and dispose of missions will allow our environment to cope with the continuous growth of space traffic and more complex operations.
Distribution of space debris around the Earth. Credit: ESA
We must consider the space environment as a shared and limited natural resource. The continuous creation of space debris leads to Kessler syndrome, when when the density of objects in low Earth orbit is sufficient, the collision between objects and debris creates a cascade effect, each crash producing debris, which then increases the chance of further collision. At this point, some orbits around the Earth become completely homeless.
ESA is actively working to support guidelines for the long-term sustainability of outer space operations from the UN Committee on the Peaceful Uses of U-Space, funding the world’s first mission to remove part of the debris from orbit, internationally creating space sustainability rating and collision evasion automation. Since develops technology to reduce the impact on our environment.
The agency’s upcoming meeting on ESA’s space debris and clean space offices and the space debris – the largest in the world – is taking place in April 2021 as part of the space security program.
