Spacefaring nations have been working since 2002 to reduce the risk space junk poses to the satellites that enable modern life. These efforts are focused on slowing the creation of more debris, but technology also is emboldening a new approach to the problem: collecting junk that’s already out there through a process known as active debris removal.
Japan, the United Kingdom and the European Space Agency (ESA) are among those leading the way.
Japan-based Astroscale took a big step forward in December 2024 when it positioned an inspection satellite within 15 meters of an old upper rocket stage during a Japanese space agency mission called ADRAS-J, for Active Debris Removal by Astroscale-Japan. In the follow-on ADRAS-J2 mission, Astroscale in fiscal year 2028 will return to the same object — from a Japanese H-2A rocket left on orbit after a 2009 launch — to grapple it and lower it toward Earth’s atmosphere for friction to incinerate it.
The company also is developing a spacecraft to remove two inactive British satellites from orbit, a project called the Cleaning Outer Space Mission through Innovative Capture, or COSMIC. In addition, the U.K. has selected Switzerland-based ClearSpace to develop an active debris removal (ADR) system for moving multiple dangerous objects out of space. This mission is called Clearing of the LEO Environment with Active Removal, or CLEAR.
Finally, ClearSpace also leads a team scheduled to deorbit an ESA Earth observation satellite in 2029 to demonstrate ADR technologies — and as a first step in establishing a new and sustainable commercial line of business. The two ClearSpace missions are complementary, Luc Piguet, company CEO and co-founder, told Apogee. “ESA’s mission proves out the full technical and regulatory framework for debris removal at scale, while the U.K. mission demonstrates agility, responsiveness and reusability. Both are critical steps toward building a sustainable orbital economy.”
The Astroscale and ClearSpace missions target objects where the danger of one smashing into another to create more debris is greatest — low Earth orbit (LEO). At altitudes of 100 kilometers to 2,000 kilometers, LEO is home to multisatellite constellations that number in the thousands, as well as the International Space Station and the Chinese Communist Party’s (CCP) Tiangong space station. ADR may also be used to move defunct satellites that are farther out in geosynchronous orbit (GEO), beginning at about 36,000 kilometers. Here, satellites typically save the last of their precious onboard fuel to propel them 300 kilometers out into a “graveyard orbit.” The fuel that would be needed to return them to Earth’s atmosphere makes incineration impractical.
It will require ramping up these nascent efforts to seriously confront a growing accumulation of debris in space. A high priority for removal is upper rocket stages in LEO that number in the hundreds. A Top 50 list updated by space-tracker LeoLabs of California shows some of these hulks weigh as much as elephants. The largest share was launched by the Soviet Union, and the sheer mass of just one would produce a giant debris cloud in a collision.
Who would pay for removal of today’s debris and how to get permission are among the questions that threaten to hold back progress in ADR.
“Removing one or two isn’t going to really make a dent in the problem,” Hugh Lewis, then a space debris expert at the University of Southampton in the U.K., told the MIT Technology Review in February 2024. “We need a sustained plan of removals.” Also, Russia and the CCP are unlikely to let others dispose of their debris to avoid revealing “technological capabilities they do not want to share with the world,” Michelle Hanlon, a space lawyer at the University of Mississippi, told the Review.
Technology is ready
Still, those working on ADR development insist a crisis is looming and there’s no turning back from the advances they’ve achieved.
“Finding proper funding mechanisms is part of the ADR challenge,” Tim Flohrer, head of the Germany-based ESA Space Debris Office, told Apogee. “However, if we don’t do it, we have a very similar situation as we do with a lot of environmental issues — we run into exponential growth in the space debris population. Exponential growth can only be addressed in an affordable way if you do this early, before you have the big problem. The early stages of this exponential growth are what we see now.”
Said Piguet, “Technology has caught up with ambition. We’ve validated key systems in space-like conditions and are advancing our core technologies. What remains a bottleneck is the financing … Debris removal doesn’t have a traditional customer — it’s a shared risk to all orbital operators.”
“I believe we have the technology now,” agreed Clare Martin, executive vice president of Denver-based Astroscale U.S., in an interview with Apogee. “At Astroscale, we think of things in terms of three pillars — technology, policy and economics. We know we can’t solve the problem just with a core piece of technology. We have to have the policy landscape in place to enable success.”
Among the technological advances that make ADR possible are the ability to approach and hold a large piece of space debris traveling in LEO at some 28,000 kph — eight times the speed of a bullet — and match its tumbling motion. Here are other key advances, as described by Piguet.
Autonomous navigation: Precise, autonomous rendezvous and proximity operations (RPO) with the improvement of on-board processing, along with guidance, navigation and control software featuring navigation supported by artificial intelligence. These capabilities enable spacecraft to approach and capture “noncooperative targets.”
Robotics for capture: Space-grade robotic arms and magnetic capture mechanisms that can physically secure irregular, tumbling or uncontrolled objects — “something that was science fiction just a decade ago,” Piguet said.
Miniaturization and modularity: Smaller, smarter and more modular spacecraft systems that make missions like ClearSpace-1 possible without a shuttle-sized platform, lowering technical and cost barriers.
Ground segment integration and simulation: Digital twins, or virtual representations of real-world systems, along with testing environments and end-to-end mission simulation, so the spacecraft’s “brain” can be trained on Earth. This ensures that capture scenarios and software can be validated under realistic conditions before launch.
Videos posted by ClearSpace and Astroscale showcase the orbital ballet that will typically constitute ADR — navigating a solar-panel winged spacecraft along a winding path toward its satellite target, circling the target for inspection, RPO to lock in on the target’s movement, connecting by magnet or claw, lowering the target’s orbit to accelerate atmospheric reentry, then releasing the target for incineration.
The final step shown is often the spacecraft heading back out for the next job. Said Flohrer, “If it’s only one launch per removal of object, then it doesn’t make much sense.”
In December, Astroscale’s ADRAS-J demonstration spacecraft proceeded through these steps, ending as planned after it locked in on the rocket body. The spacecraft aligned with the rocket’s relative speed, distance and attitude, and maintained this position. But then an unexpected change in the relative positions of the two spacecraft triggered an autonomous, onboard collision avoidance system. After holding as close as 15 meters, the spacecraft pulled off, never reaching the planned capture initiation point. Nonetheless, the mission succeeded in providing critical data for ADRAS-J2 “and set a new benchmark for space sustainability,” Astroscale reported on its website.
Full service in space
The technology at the heart of ADR will also help enable a broader spectrum of operations known as ISAM, for in-space servicing, assembly and manufacturing. Among the services planned are refueling, repair and repositioning. “By solving for the hardest case — capturing uncontrolled, tumbling debris — we’re building trust and technical competence that future missions can rely on,” Piguet said. “ADR platforms are essentially multifunction orbital vehicles capable of both debris removal and other servicing tasks.”
Said Flohrer, “There is overlap between the two technologies. And for efficient in-orbit servicing, you need an environment without too many issues of space debris in your operations. Because if you try to service something, and you get a close approach with a piece of space debris, then you have to abandon your servicing.”
An evolving capability globally, on-orbit servicing is considered largely experimental by NASA and the U.S. Department of Defense, according to a July 2025 report from the U.S. Government Accountability Office (GAO). The report said the “agencies have not pursued operational robotic servicing missions and have not fully committed to requiring their satellites be designed for servicing.” The reason, in the case of the DOD: The agency is moving toward using large groups of smaller, shorter-lifespan satellites in LEO, prioritizing satellite replacement over repair and reducing the need for servicing capabilities, the GAO said.
U.S. Space Policy Directive 3 says, “The United States should pursue active debris removal as a necessary long-term approach to ensure the safety of flight operations in key orbital regimes.” But NASA notes at its debris mitigation page that no U.S. government entity has been assigned the task of removing existing on-orbit debris.
Still, the U.S. Space Force is moving ahead with plans to test commercial, in-space satellite servicing, with Astroscale scheduled for a refueling launch in mid-2026, Martin said. The company will help “fill ’er up” during a satellite rendezvous just beyond GEO using hydrazine, a clear liquid propellant that is stable for long missions. GEO is home to Space Force missions such as the Geosynchronous Space Situational Awareness Program, made up of maneuverable surveillance satellites that watch what’s happening in space. U.S. companies Northrop Grumman and Orbit Fab also are working with the Space Force to test refueling technology.
“Refueling offers a unique and a different set of capabilities,” Martin said. “Most importantly, responsiveness. In the time it takes you to make a decision and launch something and get to orbit, if you have a refueling capability on orbit, you can respond to the need much quicker.”
For Astroscale, financial success is tied to creating demand for the complete range of on-orbit services it aims to offer. “We’ve never pulled ADR apart,” she said. “We’re focused on on-orbit servicing in general, so it’s an embedded part of our business plan, especially globally. We have a company business plan which has different services — refueling, life extension.”
Making ADR commercially viable, then, may depend on whether demand grows for all in-space services. The ESA is working to build that demand among its 22 member nations through the agency’s sweeping Space Safety program, addressing challenges such as asteroid strikes, the threat from solar weather — and space debris.
“First of all, our strategy is to demonstrate that active debris removal is possible,” Flohrer said. The ClearSpace-1 project is part of that effort. “ESA would then be a customer for such commercial services. But I think it’s safe to assume that if ESA is the only customer, it’s not a sustained concept. We are not operating very many objects. Our job is to get the technology to the market.”
The number of objects in orbit is increasing. In order to be able to just manage that environment, ensure that we’re doing it safely and sustainably and also honestly — especially for national security assets — we’re going to have to use all the tools in the toolbox.” ~ Clare Martin, executive vice president of Astroscale U.S.
Piguet of ClearSpace called public procurement and coalition funding crucial to pushing ADR forward, but like Martin, he predicts a commercial market for the service will follow. Just as critical as the technological advances, he said, ESA’s leadership in spearheading active debris removal “signals institutional confidence. Regulatory and public interest is now aligned with technological readiness.” He added, “The commercial space sector is growing rapidly, and protecting valuable orbital infrastructure is becoming a business necessity. This creates market demand for in-orbit servicing and debris removal — not just as a public good, but as a commercial service.”
As a good start, Piguet envisions a schedule of three to five missions per year for ClearSpace, supported by a mix of public funding and commercial contracts. “Over time, we foresee a model where orbital servicing becomes routine — just another part of space operations.”
Another tool for cleaning up space is recycling, Martin said. “Active debris removal to us at Astroscale doesn’t necessarily mean bringing it back into the Earth’s atmosphere,” she said. “It could equally mean, in the future, repurposing it or recycling it some way in orbit. Create a more circular economy in orbit.”
One example: Astroscale has partnered with CisLunar Industries of Colorado and Colorado State University, under a contract with the Space Force, to convert space debris into propulsion fuel rods — a process CisLunar likened to “using your compost pile to fuel your car.” A servicing vehicle would capture the debris, deliver it to a salvage platform for conversion, then use the resulting propellant canisters to fuel its journey to deliver more canisters to another point of use. Still other tools have been considered, as noted in the 2021 ESA video “Time To Act,” like solar sails and balloons to slow down satellites so they can burn up safely.
Creating less junk
Clearing debris that peppers working orbits is one way to clean up space. Creating less debris is another. This line of effort has generated far more global interest and involvement than ADR, including the development of guidelines and protocols affecting launch, deployment and deorbiting for today and into the future. Said Flohrer, “From ESA’s perspective, mitigation and removal, remediating the environment, has to work hand in hand.” Added Martin, “I think both will be required.”
The world got serious about the threat with the creation of the Inter-Agency Space Debris Coordination Committee (IADC) and the release in 2002 of its first debris mitigation guidelines. The guidelines have been updated four times, most recently in January 2025 to account for the proliferation of multisatellite constellations in LEO.
Nations and organizations have issued their own standards through the years, all of which inform the IADC’s efforts. But only the IADC recommendations represent a consensus by 13 of the world’s major spacefaring nations. They form the basis for guidelines adopted by the U.N. Committee on the Peaceful Uses of Outer Space (COPUOS). The fundamental principles: Prevent explosive on-orbit breakups and the expanded collision risk they pose, remove old spacecraft from working orbits, and limit objects released from spacecraft during normal operations.
The 18 pages of guidelines drill deep into how to accomplish these goals — encouraging, for example, designs that minimize the risk of stored fuel exploding, adding devices to spacecraft to improve their trackability, and maneuvering objects toward incineration no more than 25 years after they quit working. This timeline was reduced to five years in 2022 by the U.S. Federal Communications Commission and in 2023 by the ESA. The new standard is part of the ESA Zero Debris Charter to slash debris levels by 2030, backed by more than 100 nations and groups.
Adherence to space debris standards is slowly improving, especially in the commercial sector, according to the 2025 ESA Space Environment Report. Between 60% and 90% of all rocket body mass reaching end of life during the past decade does so on orbits that are estimated to adhere to the 25-year lifetime limit, the ESA report said. Much of this is credited to controlled reentries after launch — a practice that increased from 10% to over 65% during the past decade. In 2024, controlled reentries of rocket bodies outnumbered uncontrolled reentries for the first time.
All the world’s effort so far, though, “is not enough to stop the increase of the number and amount of space debris,” the ESA report concludes, noting that there’s a long trend line to reverse: “Ever since the start of the space age on the 4th of October 1957, there has been more space debris in orbit than operational satellites. … only a globally supported solution can be the answer.”
Broader compliance would help. COPUOS keeps a list of standards adopted by selected states and international organizations, about 60 all told. Many invoke the IADC guidelines. According to a state-by-state COPUOS summary, the standards range in rigor from an eight-page summary listing just the titles of applicable U.S. law and policy to the single line one nation submitted to the agency: “Tunisia has not yet adopted mechanisms or standards related to space debris mitigation but continues to keep abreast of the issue.” A skeptical Spain makes note of “questions regarding States’ jurisdiction and control over registered space objects, as well as liability for damage resulting from debris remediation operations.”
What’s in debris?
Even universal compliance will never preclude the need for ADR as an ongoing service, its proponents argue. The Space Environment Report points to the potential for a feared cascade of devastating debris collisions. “To prevent this runaway chain reaction, known as Kessler syndrome, from escalating and making certain orbits unusable, active debris removal is required,” the report said. “Even the best possible space debris mitigation fails, because it’s a technical system,” Flohrer said. “So you have somebody who can tow you.”
Their size, position and durability make derelict rocket bodies the top priority for ADR. “The important thing is to start with the worst offenders — just as you’d start clearing a road by moving the biggest truck blocking traffic,” Piguet said. “Today, the top 50 to 100 objects represent the bulk of the risk.” Space debris expert Lewis told the MIT Technology Review that stopping the rotation of a derelict rocket and pushing it back into the atmosphere would require a spacecraft nearly the size of the rocket itself. “If it’s tumbling end over end, you need a really capable system to manage that angular momentum.”
From there, increasingly smaller space debris may someday become targets for ADR. “We’re talking about roughly 30,000–40,000 trackable objects today,” Piguet said. “Not all are suitable for removal — some are active, others are too small. … Over time, with better tracking, even centimeter-scale targets may become addressable.” The smallest objects that can be tracked with today’s technology are 10 centimeters, about the length of a playing card. Add in nontrackable debris, and space debris is estimated to number in the millions of objects.
There’s a wide variety of debris in space, just as in terrestrial junkyards. In addition to rocket stages and dead satellites, pieces of spacecraft are left after collisions and explosions, paint flakes off, and astronauts let slip a glove or a camera. Explosions can occur with erosion of rubber gaskets that separate the leftover fuel and oxidizer in a derelict rocket’s propellant tanks. “In five or 10 years, the two might mix, you might get a huge bang, and one piece of space junk might become one thousand,” Smithsonian Observatory astrophysicist Jonathan McDowell told Harvard Magazine in June 2025.
Clean orbits are vital to the navigation, communication and surveillance satellites upon which modern life has come to depend. As the “Time to Act” video said, “By reaching into space, we have brought huge benefits down to Earth, providing technologies that enrich our societies, connect people in previously unimaginable ways and give us an incredible perspective and understanding of our planet.” One measure of space’s importance is declaring it a warfighting domain, as the U.S. and other nations have done, where military might will be used to protect spacecraft.
“It is a unique asset that is so beneficial to us on planet Earth,” Martin said. At the same time, “The number of objects in orbit is increasing. In order to be able to just manage that environment, ensure that we’re doing it safely and sustainably and also honestly — especially for national security assets — we’re going to have to use all the tools in the toolbox.”
Added Flohrer, “What’s important for me is that we understand space has limited capacity and we are at risk of losing this resource.” Preserving it requires action, he said. “Active debris removal is an essential technology, a crucial steppingstone to make this happen.”