Even if all space launches were halted tomorrow, the amount of debris would continue increasing: levels of debris in low orbits are inexorably rising, mainly driven by collisions. As the number of individual items of debris increases, further collisions are bound to follow. The most effective way to stave off this chain reaction and stabilise the debris population in key orbits is to remove large items of debris from space.
Clean Space is studying an active debris removal mission called e.deorbit, which would target an ESA-owned derelict satellite in low orbit, capture it, then safely burn it up in a controlled atmospheric reentry. The mission is being prepared for approval during the next ESA Council at Ministerial level in late 2016, for a projected launch in 2023. At present there are two concepts under consideration: one using a net and the other a robotic arm.
Such an automated capture and deorbit of an uncooperative object has never before been performed. Making e.deorbit happen requires substantial progress across multiple technology domains such as capture mechanisms, guidance and navigation, image recognition and onboard processing.
One of the challenges is that non-operational satellites have a tendency to start to tumble. This tumbling needs to be fully studied and understood before a final capture method can be selected.
e.deorbit will be the world’s first active debris removal mission, and will provide an opportunity for European industries to showcase their technological capabilities to a global audience.
e.deorbit will place European industry as the world leader in the space debris remediation effort, through the development and implementation of cutting-edge technologies in the following areas:
- non-cooperative rendezvous and formation flight
- capture and control of large non-cooperative objects
- adaptive guidance, navigation and control
These developments will pave the way for the creation of new services and markets (e.g. in orbit servicing).
The objective of the mission is to use a custom spacecraft to capture a heavy, ESA-owned item of debris and remove it from an altitude of 800 to 1000 km and a near-polar orbital trajectory. This removal will be performed by moving the item at high speed and high precision into Earth’s atmosphere, causing it to burn up.
At this stage, the emphasis is on mastering various technologies to make e.Deorbit workable in practice. Some of the most important are described below.
Drifting satellites are prone to tumbling in unpredictable ways. The e.Deorbit spacecraft will have to identify its target – potentially autonomously – and then assess its condition and rate of spin before going on to perform a close approach.
The target item of debris next has to be captured and robustly secured. Possible capture mechanisms under study include nets, harpoons and robotic arms.