It’s been an active spring on the space debris mitigation front. The European Space Agency has announced 12 countries and more than 40 companies and NGOs have joined as initial signatories to the Zero Debris Charter, which establishes the goal that by 2030, future space missions should be conducted in a way that creates no net addition of debris in orbit. A workshop focused on the technical details of implementation of this Charter is scheduled for late June. Similarly, in April 2024, the Indian Space Research Organisation (ISRO) announced its intent to have “Debris Free Space Missions (DFSM)” by 2030 (in which all space missions conducted by Indian space actors should be “debris-free”). In the United States, in early May, the Federal Communications Commission (FCC) stated its intent to refresh the record concerning orbital debris mitigation requirements for large constellations, ultimately seeking “to improve and clarify its rules” on this topic. The FCC’s Chairwoman, Jessica Rosenworcel, also issued a statement on May 29, 2024, noting, “Our orbital debris mitigation efforts will help preserve the orbital environment to protect services we rely on and allow new services to be launched.”
Collectively, these initiatives and commitments reinforce the necessity of reducing collision risk in Earth’s orbit and enhancing the long-term sustainability of the space environment. They emphasize the importance of mitigating the creation of future debris as a key enabling factor for increasing the benefits from space activities and the space economy, and for protecting access to space for future generations and users. In addition, details within them also highlight the need to understand the impacts of human-made space debris on other aspects of Earth’s environment and terrestrial safety.
This momentum is welcomed. But at the same time, it calls attention to the need to also maintain focus on the other aspect of the space debris challenge: remediation of the existing space debris population resulting from legacy activities.
The recently released Volume 1 of NASA’s Space Sustainability Strategy, which focuses on space sustainability in Earth orbit, notes that more than 25,000 space objects (including active satellites, defunct satellites, rocket bodies, and various debris objects) are being tracked in orbit, while there could potentially also be millions of smaller, untrackable objects. NASA further estimates that:
- “25 percent of tracked objects are debris from nominal space operations (including defunct spacecraft, rocket bodies, and items intentionally released during missions)
- About 50 percent of tracked objects were created during fragmentation events (such as (antisatellite tests and self-sabotage, explosion of propulsion systems or batteries, and accidental collisions).”
These are existing objects. Their creation cannot be mitigated – it must be remediated.
Mitigation of future debris creation will not reduce the operational and environmental risks posed by these existing objects. For that, further efforts on orbital debris remediation – reduction of collision risk from existing debris through a variety of technologies and processes – are needed.
Remediation of existing debris objects has been, and remains, a difficult technical, political, and business challenge to solve. Most risk from large debris objects in low Earth orbit results from the activities of legacy governmental activities – for the most part, that of the United States, Russia (including historical Soviet objects), and China. There is no commercial market for removing these objects; geopolitical considerations have limited international cooperation; and public safety and responsible arguments have so far not been successful in catalyzing action. Technical challenges associated with the removal of unprepared debris objects (those objects not designed for or actively participating in a removal, e.g. defunct rocket bodies or satellites) also have been a high barrier. Concepts for just-in-time debris remediation – in which potential collisions are avoided by nudging or changing the trajectory of debris objects – remain largely conceptual.
However, a number of trends and activities are reducing the technical challenges with debris remediation and active debris removal (ADR) concepts. Development of adjacent capabilities in satellite servicing, refueling, and in-space logistics – where there are more easily identified addressable markets – are helping to advance ADR-related technologies in commercially relevant rendezvous and proximity operations as well as in spacecraft grappling, berthing, and docking capabilities. Commercial space situational awareness and non-Earth imaging capabilities and services enhance the ability to conduct characterization of debris objects and inform safe rendezvous operations. Further, companies are investing internally in novel debris remediation concepts, such as laser-based ablation and in-space recycling.
Most significant, however, are a number of ADR or debris remediation pilot and technology development programs underway in Europe, Japan, and the United Kingdom. The European Space Agency has funded the Clearspace-1 mission which will remove the defunct European Proba-1 satellite, with a target date in 2026 (somewhat ironically, the target spacecraft for this mission was changed in April 2024 as a result of the original target, a Vega rocket upper stage, being involved in a debris-creating event ). The United Kingdom Space Agency is funding a national mission to remove a pair of defunct UK satellites, also in 2026, with the intent that the spacecraft conducting the removal be refuellable. A selection of performers for Phase II of the UK National Active Debris Removal (ADR) Mission Technology Development is expected in July 2024. This phase will focus on “understanding of risks and costs associated with a UK Active Debris Removal mission.” In Japan, JAXA has funded the Commercial Removal of Debris Demonstration (CRD2) program which aims to cooperate with Japanese private companies to remove an unprepared Japanese upper-stage rocket body from LEO.
Commercial firm Astroscale has completed the ELSA-D mission, which demonstrated some key technologies for debris removal, and is currently performing the ADRAS-J mission, funded by JAXA under CRD2, which has the objective of approaching and characterizing an existing piece of large debris. In April 2024, Astroscale was selected to perform Phase II of the CRD2 program. European firms OHB and ClearSpace are responsible for the development and operations of the ClearSpace-1 mission. ClearSpace and Astroscale are both performing work for the United Kingdom Space Agency mission.
These initiatives are positive, but there is a need for additional government action, both to sustain and scale existing programs and to involve additional governments. Most of the pilot programs for debris remediation are in Europe, the UK, and Japan, although there have been a few other countries supporting minimal programs along these lines. In January 2022, China’s Shijian-21 spacecraft docked with and towed a defunct BeiDou navigation satellite to a graveyard orbit above geostationary orbit; as a capability demonstration. In the United States, the Air Force Research Laboratory’s Orbital Prime program has awarded a number of small research and development contracts to US firms for the development of ADR-related technologies; and the long-term objectives of the program include conducting an on-orbit demonstration of ADR.
Otherwise, there is little public progress on large-scale debris remediation from the governments associated with the largest source risk from legacy objects (United States, China, and Russia). The pilot programs in Europe, the United Kingdom, and Japan address objects from those jurisdictions, but not from the largest pool of risk from historical activities.
NASA’s Space Sustainability Strategy may represent the beginning of a change in the way the US government approaches this topic. The Strategy includes a policy change in NASA’s role relative to debris mitigation. It notes that NASA’s previous policy on debris remediation restricted the Agency’s ability to meaningfully “support the development and use of remediation capabilities.” The Strategy then announces a three-part change to this policy allowing NASA to: fund debris remediation technology efforts “without constraints on the technology readiness level of the initial or resulting technologies”; “fund the development of operational capabilities for debris remediation”; and “take action to remediate its own debris or debris that directly threatens NASA’s missions.” This is a significant and welcome policy change. To be fully meaningful, further leadership is required with follow-up implementation support and funding.
Part of the challenge that has limited prior NASA involvement in debris remediation – as well as more general investment in ADR and other large debris remediation capabilities – has been a belief that the costs of doing so outweighed the benefits; compared to the costs and benefits of mitigation and tracking efforts. In May of this year, NASA’s Office of Technology, Policy, and Strategy released a study entitled the Cost and Benefit Analysis of Mitigating, Tracking, and Remediating Orbital Debris which argues that this has changed. The study compares the costs and benefits of a number of debris remediation, mitigation, and tracking efforts in dollars. Part of the methodology assesses “space sustainability in terms of monetary risk to spacecraft operators.” The study finds that “debris remediation capabilities can provide just as much risk reduction per dollar spent as tracking and mitigation can.” It also reports that “the most effective form of remediation is just-in-time collision avoidance, which nudges large debris away from possible collisions.”
In February 2024, Secure World Foundation and LeoLabs hosted an Orbital Debris Remediation Summit, which gathered representatives from space agencies, academia, and industry to discuss how the community can make progress on orbital debris remediation, especially for large debris objects. The event noted that while government-funded technology development programs and pilot debris remediation efforts like those noted above are making progress on maturing technology and operations concepts, there is a need to focus on the “means to collectively address how to catalyze the operational deployment of remediation missions to include active debris removal.”
There is a scientific consensus that removing or remediating orbital debris is critical for space sustainability, but there are still debates over the best strategy for doing so. There are many policy, diplomatic, legal, and business challenges in moving from research and demonstration to implementation of remediation programs. The upcoming 6th Summit for Space Sustainability, co-hosted by Secure World Foundation and the National Space Policy Secretariat of the Cabinet Office, Government of Japan, in Tokyo, Japan, July 11-12, 2024, will include a focus on the relationship of debris remediation to broader space sustainability progress. Keynotes, panels, and other sessions will discuss next steps on debris remediation and consider such questions as:
- Should the focus be on removing the many small untracked objects that pose current threats to active satellites or the very massive objects that will drive long-term threats?
- What are the biggest obstacles to making remediation real?
- How does debris remediation fit into the broader ISAM landscape and marketplace?
- Is it possible to take concrete steps to encourage further governmental action, and cooperation, to address legacy debris objects
These discussions at the 6th Summit for Space Sustainability aim to highlight the actions necessary to ensure government investments in debris remediation result in sustained and scalable outcomes, which coupled together with mitigation commitments, can make meaningful progress towards solving the challenges of space debris.
Ian Christensen is Senior Director, Private Sector Programs at the Secure World Foundation. He is also Co-chair of the 6th Summit for Space Sustainability.
Secure World Foundation envisions the secure, sustainable and peaceful uses of outer space contributing to global stability and benefits on Earth.
The mission of the Secure World Foundation is to work with governments, industry, international organizations, and civil society to develop and promote ideas and actions to achieve the secure, sustainable, and peaceful uses of outer space benefiting Earth and all its peoples.
