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• ClearSpace
• in-orbit servicing
• low-Earth orbit
• orbital engineering
• proximity operations
• robotic capture systems
• satellite servicing
• space debris removal
• space sustainability
• UK Space Agency

Attribution

via spacenews.com

ClearSpace has completed Phase 2 of the UK Space Agency’s Active Debris Removal (CLEAR) mission, marking significant progress in developing technology to safely remove defunct satellites from low-Earth orbit.

The milestone represents a critical step toward addressing the growing orbital debris problem through practical engineering solutions.

The Switzerland-based company, operating through its UK subsidiary, has focused this phase on de-risking key technologies essential for the mission’s success.

With space debris increasing as more satellites enter orbit, this engineering initiative aims to establish viable methods for removing non-functional objects that pose collision risks to operational spacecraft.

Technical Advancements in Orbital Debris Removal: ClearSpace Completes Phase 2 of UK Space Agency's CLEAR Mission 1

During this phase, ClearSpace conducted comprehensive testing across several critical systems. The spacecraft’s robotic capture mechanism successfully underwent mechanical testing, demonstrating its ability to withstand launch loads exceeding several times Earth’s gravity. This structural validation confirms the system’s resilience under extreme conditions.

The company also made significant progress in sensor technologies crucial for the mission:

• Image processing algorithms were tested in realistic environments, validating their capacity to detect and track space debris against the complex background of space.
• Proximity operations were simulated using hardware-based spacecraft emulators, allowing engineers to validate key operational sequences.
• Rendezvous and proximity operations (RPO) radar systems were refined to enhance detection capabilities.

Technical validations like these are essential for any mission that requires precision, reliability, and autonomous operation in a challenging orbital environment.

The CLEAR mission has a defined operational structure. Once launched, the servicer spacecraft will:

1. Rendezvous with the first defunct satellite in its original orbit
2. Capture the object using the validated robotic system
3. Transport it to a lower altitude where atmospheric drag will cause it to burn up safely
4. Repeat the process with a second orbital debris object

This dual-target approach should provide a more comprehensive test of the new technology. The UK Space Agency has identified this capability as critical for future space sustainability efforts, particularly as the number of satellites in low-Earth orbit continues to grow.

The project highlights the collaborative nature of advanced space engineering, with several specialized partners contributing key technological components:

Critical Software developed the flight software integration system using its Karvel Onboard Software Platform, the computational foundation for all mission operations.

Indra-Deimos focused on rendezvous guidance, navigation, and control (GNC) algorithms that enable precise manoeuvring in orbit—essential for approaching debris objects safely.

Technical Advancements in Orbital Debris Removal: ClearSpace Completes Phase 2 of UK Space Agency's CLEAR Mission 2

Plextek refined the RPO radar technology to provide critical situational awareness during proximity operations, enhancing the mission’s safety margins.

Spirit AeroSystems applied its aerospace manufacturing and structural testing expertise to support development objectives, leveraging its experience in advanced aerostructures.

“By demonstrating the capability to design, build, test, license, launch, and operate this mission from the UK, we are proving that the UK has what it takes to lead in space sustainability,” said Rory Holmes, ClearSpace UK Managing Director.

The Growing Challenge of Orbital Debris: Engineering Solutions for a Sustainable Space Environment

A crisis has been quietly brewing for decades in the vast expanse above our planet. The orbital regions surrounding Earth, particularly low-Earth orbit (LEO), have become increasingly congested with human-made objects—from operational satellites providing essential services to defunct spacecraft, discarded rocket stages, and fragments from collisions and explosions. As we launch more satellites to meet our global communication, observation, and scientific needs, the risk of collisions and the creation of additional debris escalates, potentially threatening future access to space.

The Scale of the Problem

Since the launch of Sputnik in 1957, humans have placed thousands of satellites into orbit. As of early 2025, more than 7,500 operational satellites circle the Earth, with commercial satellite constellations like Starlink accounting for a significant portion. However, these functioning satellites represent only a small percentage of tracked objects.

The U.S. Space Surveillance Network tracks approximately 27,000 pieces of orbital debris larger than 10 cm. Beyond these trackable objects lie an estimated 900,000 objects between 1-10 cm and tens of millions smaller than 1 cm. Even these tiny fragments pose significant threats—travelling at orbital velocities of approximately 7-8 km/s, a collision with an object as small as 1 cm can damage or turn off a satellite, while impacts with larger debris can be catastrophic.

The problem is self-perpetuating. In 2007, China conducted an anti-satellite missile test, destroying one of its weather satellites and creating over 3,000 trackable debris fragments. Two years later, a defunct Russian Cosmos satellite collided with an operational Iridium communications satellite, generating another 2,000 trackable pieces of debris. These two events alone increased the trackable debris population by nearly 40%.

The Kessler Syndrome, theorized by NASA scientist Donald J. Kessler in 1978, describes a scenario where the density of objects in LEO becomes high enough that collisions between objects could cause a cascade—each collision generating debris that increases the likelihood of further collisions. This runaway chain reaction could render specific orbital ranges unusable for generations.

Engineering Challenges of Debris Removal

The technical challenges facing engineers attempting to solve the orbital debris problem are formidable:

Before anything can be removed, it must be precisely located and identified. This requires:

• Advanced radar systems capable of detecting small objects at orbital distances
• Optical tracking systems for higher orbits
• Complex algorithms to process sensor data and maintain a catalog of objects
• Predictive models to forecast orbital paths and potential conjunctions

Engineering teams must develop systems that can distinguish between different types of debris, assess their tumbling rates, and determine their physical characteristics—all essential information for planning a removal operation.

Approaching an uncooperative, potentially tumbling object in orbit presents significant challenges:

• Precise orbital mechanics calculations for fuel-efficient intercept trajectories
• Real-time sensing and navigation systems capable of operating in the harsh space environment
• Autonomous decision-making algorithms for final approach phases
• Collision avoidance protocols to prevent the remediation mission from creating more debris

These operations require engineering solutions that combine spacecraft propulsion, sensor fusion, and artificial intelligence systems capable of making split-second adjustments.

Once a debris object is reached, it must be securely captured without creating additional fragments. Engineers have developed several approaches:

• Robotic arms with specialized gripping mechanisms
• Net-based capture systems for tumbling objects
• Harpoon-like devices for robust attachment points
• Electromagnetic systems for metallic debris
• Adhesive or tether-based solutions

Each approach requires extensive testing on Earth and space-like conditions to ensure reliability. Material scientists must develop components that can withstand the space environment’s extreme temperature variations and radiation exposure while maintaining their mechanical properties.

After capture, debris must be removed from crowded orbital regions:

• For objects in LEO, controlled re-entry into Earth’s atmosphere (requiring precise trajectory control to ensure burn-up over unpopulated areas)
• Objects in higher orbits transfer to “graveyard orbits”, where they pose minimal risk.

These manoeuvres demand sophisticated propulsion systems, thermal protection for re-entry, and careful mission planning to minimize risks to ground populations and other space assets.

ClearSpace’s CLEAR mission represents one of the most advanced attempts to address these challenges. Their engineering approach incorporates several innovative elements:

The ClearSpace servicer spacecraft employs a modular architecture that allows for:

• Separation of critical subsystems to enhance reliability
• Radiation-hardened computing systems for operating in the LEO environment
• Redundant propulsion and power systems to ensure mission completion

This modular approach enables iterative improvements in future missions based on operational experience gained during initial debris removal operations.

Successful debris removal relies heavily on accurate sensing capabilities. ClearSpace’s system incorporates:

• Multi-spectral optical sensors for visual tracking and identification
• Custom-developed image processing algorithms that can differentiate between debris objects and the Earth or space background
• Lidar systems for precise distance and orientation measurements
• Radar technology developed with Plextek specifically for rendezvous and proximity operations

These sensors must function reliably despite challenging lighting conditions, reflection issues, and the potential for equipment degradation in the space environment.

At the heart of the ClearSpace approach is its innovative capture system:

• A four-armed robotic mechanism capable of adapting to differently shaped objects
• Computer vision-guided grasping algorithms
• Force-feedback systems to regulate grip pressure and prevent fragmentation
• Mechanical damping to absorb the kinetic energy of tumbling debris

The robotic system underwent rigorous testing to ensure it could withstand launch loads—experiencing forces several times Earth’s gravity—while remaining precise enough to handle delicate operations in orbit.

Due to communication delays and limited windows for ground control, significant portions of the mission must be performed autonomously:

• Real-time trajectory planning algorithms
• Decision-making systems with fail-safe protocols
• Self-diagnostic capabilities to detect and resolve anomalies
• Machine learning components that improve performance over time

The software architecture, developed with Critical Software using their Karvel Onboard Software Platform, integrates these autonomous functions while maintaining strict safety parameters.

Precision is essential for debris removal operations. ClearSpace’s navigation system includes:

• Star trackers for absolute positioning
• Relative navigation algorithms developed with Indra-Deimos
• Cold gas thrusters for delicate manoeuvring during approach phases
• Collision avoidance systems that continuously recalculate safety margins

These systems must perform reliably in an environment where GPS is unavailable and visual references change constantly due to orbital movement and lighting conditions.

The Role of Engineers in Solving the Debris Problem

The orbital debris challenge exemplifies the complex, multidisciplinary problems that modern engineers must tackle. Several engineering disciplines converge to create viable solutions:

Aerospace Engineering

Aerospace engineers design the spacecraft structures, propulsion systems, and thermal control mechanisms essential for debris removal missions. They must balance competing requirements, including:

• Structural integrity to withstand launch and orbital manoeuvres
• Mass optimization to minimize launch costs
• Thermal management in the extreme temperature environment of space
• Radiation tolerance for electronic components

The structural testing performed by Spirit AeroSystems during ClearSpace’s Phase 2 reflects this critical aspect of mission development.

Robotics and Mechatronics

The capture of uncooperative objects in space represents one of the most challenging applications of robotics:

• Developing mechanisms that function reliably in vacuum conditions
• Creating end effectors capable of adapting to various shapes and surfaces
• Implementing control systems that can manage the complex dynamics of two free-floating bodies
• Ensuring mechanical reliability despite extreme temperature variations

Robotics engineers must address these challenges within strict mass and power budgets.

Software and AI Engineering

Software forms the backbone of modern space missions, with debris removal requiring particularly sophisticated systems:

• Computer vision algorithms for object detection and tracking
• Guidance, navigation, and control software for precise manoeuvring
• Autonomous decision-making systems for time-critical operations
• Fault detection, isolation, and recovery systems to ensure mission continuity

Critical Software’s work on ClearSpace’s flight software demonstrates the essential role of software engineering in enabling complex space operations.

Systems Engineering

Perhaps most importantly, systems engineers integrate these diverse technologies into a coherent, reliable mission architecture:

• Defining interfaces between subsystems
• Establishing verification and validation procedures
• Managing technical risks across the entire mission profile
• Ensuring regulatory compliance and mission safety

The successful completion of ClearSpace’s Phase 2 milestone reflects effective systems engineering practices that brought contributions from multiple partners into a cohesive design.

While engineering solutions are essential, addressing the orbital debris problem comprehensively requires complementary policy and economic frameworks. No single nation can solve the debris problem alone, so engineers must work within international frameworks that facilitate the work.

Of course, prevention remains more cost-effective than fixing the problem after it occurs. Engineers are already implementing design approaches that minimize future debris:

• Passivation systems to deplete onboard energy sources at end-of-life
• Drag enhancement devices to accelerate orbital decay
• Design-for-demise principles to ensure complete burn-up during re-entry
• Standardized grappling fixtures on new satellites to facilitate future removal if necessary

If the CLEAR mission succeeds, it will represent a technical achievement and a paradigm shift in how we approach space operations—moving from a “launch and forget” model to sustainable, responsible stewardship of the orbital environment.

Today’s engineers working on debris removal are pioneering techniques that will become standard practice in future decades, ensuring that access to space remains available for generations. Their work exemplifies how engineering can address humanity’s most complex challenges, combining cutting-edge technology with environmental responsibility and international cooperation.

As we continue to rely on space-based infrastructure for communications, navigation, Earth observation, and scientific discovery, the importance of these engineering efforts will only grow. The orbital debris problem presents a crisis and an opportunity to demonstrate how human ingenuity can correct past oversights and create a sustainable path to space exploration and utilization.

Completing this phase provides the UK Space Agency with detailed programmatic estimates, offering valuable data for mission planning and resource allocation. These engineering insights are crucial for transitioning from testing to implementation.

Ray Fielding, UK Space Agency Head of Sustainability, described this as “a significant milestone in our national ADR program,” noting that the agency is “delighted that ClearSpace and partners have successfully delivered all requirements in this de-risking-focused phase of work.”

ClearSpace’s CLEAR mission is competing with another project from Japan-based Astroscale for a UK Space Agency contract to remove two defunct satellites from low-Earth orbit in 2026. This competitive process has accelerated innovation in space sustainability technologies.

With Phase 2 completed, the UK Space Agency recently hosted an engagement event outlining the next steps for the national UK ADR mission. The project is scheduled to move toward a System Critical Design Review (CDR), with a target launch date in 2026.

ClearSpace is simultaneously working on the separate ClearSpace-1 mission with the European Space Agency, building complementary expertise and technology.

If the mission succeeds, it will demonstrate practical engineering solutions to a problem that has concerned space agencies and satellite operators for decades. The ability to safely remove non-functional satellites would reduce collision risks in increasingly congested orbital regions.

The technologies being developed have applications beyond debris removal. They potentially support in-orbit servicing, assembly, and manufacturing (ISAM) capabilities. These include satellite life extension, on-orbit repairs, and component replacements—all crucial for the sustainable development of space infrastructure.

The project also contributes to establishing technical standards and operational protocols for proximity manoeuvres around non-cooperative targets, addressing a significant gap in current space operations.

By focusing on the practical engineering aspects of debris removal rather than theoretical approaches, ClearSpace and the UK Space Agency are making tangible progress toward enhancing orbital safety while developing valuable technical capabilities for the future space economy.

TLDR:

• ClearSpace has completed Phase 2 of the UK Space Agency’s Active Debris Removal mission
• Key technologies were validated: robotic capture systems, image processing algorithms, and proximity operations
• The mission will demonstrate removing two defunct satellites from orbit
• Partners include Critical Software, Indra-Deimos, Plextek, and Spirit AeroSystems
• The project advances technology for space sustainability and in-orbit servicing
• The target launch date is 2026, competing with Astroscale for the final contract

May 2025

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