Technologies for mitigating space debris

Removing space debris

EPOS 2.0 test facility
The EPOS 2.0 facility at the German Space Operations Center (GSOC) is a highly specialised research infrastructure designed to develop and test, on the ground, complex rendezvous and docking manoeuvres for use in space. With sub-millimetre positioning accuracy and a command rate of 250 hertz, the facility enables high-precision testing.
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ADEO-L braking sail successfully deployed in the laboratory
DLR's many years of research into components for satellite braking sails are now being put into practice in collaboration with the company HPS. Braking sails are designed to remove decommissioned satellites from low Earth orbit more quickly.
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TINA (This-Is-Not-an-Arm)
As part of the TINA project, DLR is developing a small, modular robotic arm designed for use in space. TINA is intended primarily for use in ISAM (In-Space Assembly and Manufacturing) applications on small satellites and to assist astronauts with tasks on space stations, such as assembly and repairs.
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Space debris poses a growing threat to spaceflight, as decommissioned satellites and debris resulting from collisions are increasingly cluttering Earth's orbits. This clutter increases the risk to active spacecraft and can also, in rare cases, pose a threat to people on the ground if debris that has not completely burned up during re-entry into the atmosphere falls to Earth.

How can decommissioned satellites and space debris be removed from orbit? Deorbiting technologies, such as drag sails, offer one possible solution. Using lasers to slow down smaller pieces of debris is another. Large, non-functional objects may be captured and towed away using robotic systems – and several in-space European technology demonstrations of this are planned for the coming years.

Deorbiting technologies and orbital manoeuvres

Modern satellites are equipped with systems which ensure that they are removed from orbit at the end of their lifetime, freeing up space for new satellites. One approach involves active flight manoeuvres using a propulsion system and remaining propellant reserves. Another approach is passive deorbiting which, for satellites in low Earth orbit, leads to re-entry even if the last propellant reserves have been exhausted. To achieve this, the surface area of the satellite is significantly increased using deployable or inflatable structures, so that it gradually loses altitude due to increased drag in the very thin residual atmosphere. DLR's space research is investigating such structures in close collaboration with industry. This work includes the deployable drag sail system for small satellites developed by the company HPS as part of the European Space Agency's (ESA) ADEO (Drag Augmentation Deorbiting System) project.

Lasers can be used to deliberately slow down or redirect smaller pieces of space debris into a different orbit in order to avoid collisions.

Robotic technologies for removing space debris

But what about large, non-functional objects? These can be captured using robotic systems and removed from orbit in a controlled manner; the relevant technologies are currently being developed and tested. Several in-space European technology demonstrations are planned for the coming years, including the EROSS IOD mission, supported by the European Commission, and ESA's RISE mission. These demonstrations will feature DLR-developed gripping systems such as the CAESAR and TINA robotic arms, the latter of which is being further developed by the DLR spin-off KINETIK Space.

To practise the complex manoeuvres for approaching non-cooperative and tumbling objects and to test the entire sequence end-to-end, DLR provides the EPOS 2.0 (European Proximity Operations Simulator 2.0) and OOS-SIM (On-Orbit Servicing Simulator) test facilities. These facilities can validate hardware such as optical rendezvous sensors and on-board computers, as well as algorithms for real-time data processing and software systems for highly automated, safe rendezvous. This work is important for preparing for challenging future missions, particularly training and testing operators prior to critical manoeuvres.

Overview of DLR's assistance and servicing systems and test facilities

ADEO – drag sails for satellites

In ESA's ADEO (Drag Augmentation Deorbiting System) project, DLR was involved in the development and testing of an ultra-lightweight, deployable sail produced by the company HPS. The sail increases the aerodynamic surface area of satellites and rocket stages, accelerating their re-entry into Earth's atmosphere. It thus serves to reduce space debris and lower the risk of collisions in orbit. The aim of the project is to provide a passive deorbiting solution that requires no additional energy or control.

ION – circular economy in orbit

The aim of DLR's ION (Impulsprojekt Orbitale Nachhaltigkeit, or 'Orbital Sustainability Impulse Project' in English) project is to develop concepts and technologies to increase sustainability in Earth orbit throughout the entire lifetime of satellites and orbital infrastructure. With ION, DLR is pooling its expertise in space, security and aeronautics, particularly in the fields of satellite operations, robotics and automation, and the observation and measurement of space debris and space weather – as well as its experience in maintenance and repair in aviation.


With ION, DLR aims to enable a circular economy in orbit. In the short term, this includes the removal of space debris, extending the operational life of satellites and developing inspection procedures. Medium-term objectives include repairs, retrofitting and in-orbit assembly, and the long-term aims include recycling and orbital depots – that is, logistical facilities in Earth orbit that serve as temporary storage sites or service centres for satellites, spacecraft or space debris.

The central focus is on developing technologies that improve the interaction between ground stations and orbital systems – for example, through the precise measurement of the rotation rate of debris to facilitate its capture.

CAESAR robotic arm

CAESAR (Compliant Assistance and Exploration SpAce Robot) is a robotic arm developed for exploration and assistance in space. It was designed for a wide range of tasks, such as assembling structures, maintaining and repairing satellites, or removing space debris. CAESAR combines innovative electronics and mechanics with new control methods. Much like a human arm, the robot has seven degrees of freedom, which gives it greater flexibility than standard robots. A 'Spacehand' fitted to the robot enables it to grasp and stabilise tumbling or non-cooperative satellites.

TINA robotic arm

With TINA (This-Is-Not-an-Arm), DLR is developing a small, modular robotic arm designed for use in space. TINA is primarily intended for ISAM (In-Space Servicing, Assembly and Manufacturing) applications such as manufacturing and assembly in space on small satellites.

In addition, the arm could be suitable for exploration missions to the Moon and Mars, where it could collect, clean and transport samples.

TINA could also be used as a 'station butler', carrying out repetitive tasks on space stations or in future lunar and Martian greenhouses, such as DLR's EDEN LUNA greenhouse, where the robot monitors and tends to plants.

EROSS IOD – service for geostationary orbit

The EU-funded EROSS IOD (European Robotic Orbital Support Services In-Orbit Demonstration) project is being carried out together with other European organisations to develop a safe and reliable service that supports satellites in low Earth and geostationary orbit. The aim is to extend the operational lifetime of satellites and make the use of space more sustainable and efficient.

As part of this project, DLR is planning and preparing a space mission to test key technologies for servicing satellites in orbit. Two spacecraft will rendezvous in space, where DLR's CAESAR robotic arm will carry out tasks such as gripping, refuelling and replacing components.

EPOS 2.0 test facility

With the EPOS 2.0 (European Proximity Operations Simulator 2.0) test facility, DLR operates a highly specialised research infrastructure designed to develop and test, on the ground, complex rendezvous and docking manoeuvres for space missions. These manoeuvres are essential for missions such as orbital servicing and towing, in which servicer satellites must carry out autonomous approaches to non-cooperative, passive satellites. As such satellites often lack any special equipment for rendezvous or docking, new navigation systems, sensors and propulsion technologies have to be developed. A further challenge is dealing with tumbling target satellites, whose uncontrolled movements must be simulated precisely and in real time.

The EPOS 2.0 facility is located at DLR's German Space Operations Center (GSOC) and serves as the central test environment for the design, development, validation and verification of rendezvous sensors and systems.

OOS-SIM test facility

OOS-SIM (On-Orbit Servicing Simulator) is a facility for simulating tasks such as assembly, servicing and repair work on satellites orbiting Earth. Researchers are also investigating the system's suitability for removing decommissioned, tumbling target satellites from orbit.

The OOS-SIM facility serves two purposes. First, it simulates the complex dynamics of multiple free-flying robots in orbit, without the influence of gravity.

Second, it provides a test platform for developing and verifying control and image-processing methods for orbital robotics. In doing so, the robot control system must reliably manage the interaction between the robot and the satellite it is mounted on, even in the absence of gravity.

Related background articles on this topic

Space safety and security

Observation of space objects

Political initiatives and international guidelines

FAQ – questions and answers

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