Technologies for space debris remediation

Debris objects in low-Earth orbit (LEO)

Simply stopping future space missions from producing more debris is not sufficient to preserve key orbits in a usable state.

A 2009 joint study of the current space debris environment performed by all major space agencies (with NASA and ESA among them) showed that even if no further space launches take place, then the space debris population will continue to increase, resulting in a continuously growing collision rate.
 
Importantly,as the total amount of debris increases, so does the probability of collisions, leading in turn to the potential irreversible pollution of orbits due to the cascading effect of collisions and feedback collisions– unless something is done to interrupt the pattern.
The study suggests that the population of large and massive objects has reached a critical density in LEO. In turn this means that the number of these objects – mostly physically intact, for now – needs to be actively controlled.
Active removal is most efficient in reducing the number of collisions and debris produced when the target objects have a high mass and high collision probabilities, being located in densely populated regions. In addition, target objects should be at high enough altitudes so that the orbital lifetime of the resulting fragments after a collision is long, and thus triggering a long term environmental impact.  

Technologies for object removal

Sources of space debris include explosions of rocket bodies
Sources of space debris include explosions of rocket bodies

Simply stopping future space missions from producing more debris is not sufficient to preserve key orbits in a usable state. 

A 2009 joint study of the current space debris environment performed by all major space agencies (with NASA and ESA among them) showed that even if no further space launches take place, then the space debris population will continue to increase, resulting in a continuously growing collision rate.
 
Importantly,as the total amount of debris increases, so does the probability of collisions, leading in turn to the potential irreversible pollution of orbits due to the cascading effect of collisions and feedback collisions– unless something is done to interrupt the pattern.

The study suggests that the population of large and massive objects has reached a critical density in LEO. In turn this means that the number of these objects – mostly physically intact, for now – needs to be actively controlled. 

Active removal is most efficient in reducing the number of collisions and debris produced when the target objects have a high mass and high collision probabilities, being located in densely populated regions. In addition, target objects should be at high enough altitudes so that the orbital lifetime of the resulting fragments after a collision is long, and thus triggering a long term environmental impact.  

ESA de-orbited the 2-tonne ERS-2 satellite in August/September 2011 into a lower-traffic orbit, offering a good example of responsible spaceflight activities.
The preservation of the space environment for spaceflight, however, is a global task and active removal is a challenge that is to be mastered in a global effort. As a technical agency and as an incubator for new technological approaches, ESA considers active removal technologies to be a strategic goal.

ATV-1 reentry

So one objective of Clean Space in this area is to streamline the technology developments required for a targeted de-orbit of a spacecraft, with system studies planned to consider this. Advanced guidance, navigation and control sensors and techniques will be needed first to dock with a target should it prove to be non-cooperative and then to control it for manoeuvring, once captured. 

Since active removal needs to be applied on a broad scale, the dynamic characteristics of various potential targets need to be analysed. In an approach consisting of measurements and modelling, the attitude motion of large decomissioned space systems needs to be characterised and understood. This is essential because the selection of capture mechanisms depends on this factor. 

Clean Space will build on existing research by ESA and its national space agency partners, such as the Agency’s RObotic GEostationary orbit Restorer (ROGER) study for a roving debris-removal robot and the German Aerospace Center DLR’s Deutsche Orbital Servicing mission (DEOS) twin-satellite mission to investigate capture and control techniques. 

Road map - Branch 4 Technologies for space debris remediation

Last update: 21 January 2014

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