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Debris and missing launcher stages in the geostationary ring. Aging satellites are known to release debris and explosions can occur due to residual energy sources. The resulting fragments can be thrown backwards and cross the geostationary orbit. For this reason, it is essential to release residual energy once the nominal mission is completed. ESA / ID and Sense / ONiRiXEL, CC BY-SA 3.0 IGO
Swirling fragments of past space efforts are trapped in orbit around Earth, threatening our future in space. Over time, the number, mass, and area of these debris objects grow steadily, increasing the risk to operating satellites.
ESA’s Office for Space Debris constantly monitors this constantly evolving debris situation and each year publishes a report on the current state of the debris environment.
Since the beginning of the space age in 1957, tons of rockets, spacecraft, and instruments have been launched into space. Initially, there was no plan on what to do with them at the end of their lives. Since then, the number has continued to rise and explosions and collisions in space have created hundreds of thousands of dangerous debris fragments.
Despite advances in technology and in understanding the space environment, Europe’s largest space debris conference has identified the need to significantly increase the pace of implementation of proposed measures to reduce debris creation. Credit: ESA, CC BY-SA 3.0 IGO
“The biggest contributor to today’s space debris problem is explosions in orbit, caused by excess energy (fuel and batteries) on board spacecraft and rockets. Despite measures in place for years to prevent this, we do not see a decrease in the number of such events. Trends towards end-of-mission elimination are improving, but at a slow rate, ”explains Holger Krag, Head of the Space Security Program.
“In view of the constant increase in space traffic, we need to develop and provide technologies to make debris prevention measures fail-safe, and ESA is doing just that through its Space Safety Program. In parallel, regulators must more closely monitor the state of space systems, as well as global adherence to debris mitigation under their jurisdiction ”.
Now there are international guidelines and standards that make clear how we can achieve sustainable use of space:
- Design rockets and spacecraft to minimize the amount of ‘detachment’ – material is detached during launch and operation, due to harsh conditions in space.
- Prevent explosions by releasing stored energy, ‘passivating’ spacecraft once at the end of their lives
- Move missing missions out of the way of working satellites, either by clipping them or moving them into a ‘graveyard orbit’
- Avoid collisions in space by carefully choosing orbits and performing ‘collision avoidance maneuvers’.
Many space agencies, private companies and other space actors are changing their behavior to adhere to these guidelines, but is this enough?
Worrisome trends
The objects we send into orbit take up space, as does the debris they create. The increasing area of objects in space dramatically increases the probability of collisions. Red (PL) = Payload; Orange (RB) = Rocket body; Dark green (RM) = Object related to the rocket mission. Credit: ESA
The number of junk objects, their combined mass, and the total area they occupy has steadily increased since the beginning of the space age. This is reinforced by a large number of in-orbit ruptures of the spacecraft and rocket stages.
The total area that space debris occupies is important, as it is directly related to the number of collisions we expect in the future. As it stands, collisions between debris and working satellites are predicted to outpace explosions as the dominant source of debris.
There are many ways to create debris in space. For each “fragmentation event”, thousands of pieces of hazardous debris can be added to Earth’s orbit. Credit: ESA
Events that create debris have become more common
On average, over the past two decades, there have been 12 accidental ‘splits’ in space each year, and this trend is sadly increasing. Fragmentation events describe times when debris is created due to collisions, explosions, electrical problems, and even simply the detachment of objects due to harsh conditions in space.
On the bright side
More satellites, or “payloads”, sent into low Earth orbit are trying to sustainably comply with debris mitigation measures than 20 years ago. However, progress is still too slow. Credit: ESA
Attempts are being made to follow the rules (not enough yet)
While not all satellites currently meet international guidelines, more and more space actors are trying to abide by the rules. In the last decade, 15-30% of objects or ‘payloads’ launched into unsupported orbits in the low Earth orbit region (excluding spacecraft related to manned spaceflight) had attempted to comply with mitigation measures of waste. Between 5% and 20% did so successfully, peaking at 35% in 2018 due to active desorbitation of the Iridium constellation.
80% of rockets launched now attempt to “clear” low Earth orbit, the vast majority of which do so successfully, compared to just over 20% at the beginning of the millennium. Credit: ESA
More rockets are being safely disposed of
When it comes to rockets, more and more are being disposed of in a sustainable way. Between 40 and 80% of those in low Earth orbit that did not meet this decade tried to comply with debris mitigation measures. In total, 30-70% of the rockets that were not naturally compliant successfully cleared low Earth orbit.
Of all rockets launched in the last decade, 60-80% (in terms of mass) adhered to mitigation measures. Some rockets are in low Earth orbits that cause them to decompose naturally in Earth’s atmosphere, but a significant number of rockets are directed back into Earth’s atmosphere, where they burn or are forced back into. uninhabited areas. These practices are increasing, with about 30% of rockets re-entering in a safe and controlled manner since 2017.
This are very good news. Rocket bodies are among the largest objects we send into space and are at high risk of being involved in catastrophic collisions. All steps must be taken to ensure that they do not remain in orbit after a maximum of 24 hours from launch.
The number of small satellites launched into near-Earth orbit has increased dramatically in the last 10 years, in part due to the increase in satellite constellations. Credit: ESA
More satellites place in low altitude orbits where they naturally burn out
The amount of “traffic” launched towards the protected region of low Earth orbit (up to 2000 km altitude) is changing significantly, in particular due to the proliferation of small satellites and constellations.
About 88% of the small payloads launched to this region will naturally adhere to space debris mitigation measures due to its low altitude, which means they break up in the Earth’s atmosphere.
It is estimated that 30-60% of the entire mass of satellites (excluding manned spaceflight) adhere to end-of-life guidelines for the same reason.
“The accelerating increase in satellites launched into low Earth orbit is clearly visible in our latest report,” explains Tim Florer, Director of ESA’s Office of Space Debris.
“We have seen fundamental changes in the way we use space. To continue to benefit from the science, technology and data provided by operations in space, it is critical that we achieve better adherence to existing space debris mitigation guidelines in spacecraft design and operations. It cannot be emphasized enough, this is essential for the sustainable use of space. “
Several times in recent years, all geostationary orbit satellites tried to responsibly move out of the way once they reached the end of their mission. Credit: ESA
High rates of debris mitigation in geostationary orbit
The satellites launched to the geostationary protected region, 35,586 – 35,986 km altitude, have very high rates of adherence to debris mitigation measures. Between 85% and 100% of those who reached the end of their life in this decade tried to comply with these measures, of which 60 – 90% did so successfully.
In the geostationary orbit, there is a clear commercial interest for operators to keep their paths free of defunct satellites and debris; otherwise, your spaceship and your bottom line are at serious risk.
Now what?
Systematic analysis of changing behaviors in space, when it comes to the adoption of debris mitigation measures, provides reason 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 enable our environment to cope with the continued increase in space traffic and increasingly complex operations.
Distribution of space debris around the Earth. Credit: ESA
We must think of the space environment as a shared and limited natural resource. The continuous creation of space debris will lead to Kessler syndrome, when the density of objects in low Earth orbit is high enough that collisions between objects and debris create a cascading effect, each collision generates debris which then increases the probability. of more collisions. At this point, certain orbits around the Earth will become completely inhospitable.
ESA is actively working to support the guidelines for the long-term sustainability of outer space activities of the United Nations Committee on the Peaceful Uses of Outer Space, including funding the world’s first mission to eliminate a piece of debris from orbit, helping to create a space sustainability rating and development 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 Spaces offices, both part of the Space Safety Program, and the Agency’s upcoming conference on space debris, the world’s largest on the subject, taking place in April 2021.
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