A world-first mission to show how space junk can be removed with technology has blasted into space.
The UK-led mission was initially due for launch on Saturday but, due to technical concerns, was postponed until Monday morning.
There is approximately 9,200 tonnes of space debris, with 34,000 objects greater than 10cm and 128 million objects from greater than 1mm to 1cm, according to the European Space Agency.
It estimates there have been more than 560 break-ups, explosions, collisions or anomalous events resulting in fragmentation.
Bits of space junk, which fly through orbit at up to 18,000 miles per hour, can threaten other functioning spacecraft and pose safety risks to astronauts on the International Space Station.
Why is space junk problematic?
While rocket launches have placed about 10,680 satellites in Earth’s orbit since 1957, around 6,250 of these are still in space, but only 3,700 are still functioning.
A collision with space debris could have a big impact on satellite services people rely on every day, including mobile phones and online banking.
On Monday, two spacecraft – a servicer satellite to collect the debris and a client satellite to act as the debris – launched from Kazakhstan on a Soyuz rocket operated by GK Launch Services.
The End-of-Life Services by Astroscale demonstration (ELSA-d) will be operated from the In-Orbit Servicing Control Centre – National Facility at the Satellite Applications Catapult (SAC) at Harwell Campus in Oxfordshire.
It is expected to start major demonstrations in around June or July.
How does the space junk removal work?
Two bits of machinery are involved in the mission, there is a large 175kg servicer aircraft which has been designed to capture and safely remove space junk, and a smaller 17kg "client" - which has been designed to look and act like a piece of space junk for the test.
The servicer will chase down the client, latching on to it using magnets, before releasing it to try again.
It is designed to show how space junk removal could work in different situations including when the junk is tumbling.
After the demonstration both parts are designed to come out of orbit and burn up in the Earth's atmosphere so they don't end up becoming space junket themselves.
The servicer satellite has been developed to safely remove debris from orbit, equipped with proximity rendezvous technologies and a magnetic docking mechanism.
The client satellite is a piece of replica debris fitted with a plate that enables the docking.
During the mission, the servicer will repeatedly release and dock with the client in a series of technical demonstrations, indicating the capability to find and dock with defunct satellites and other debris.
Demonstrations include looking for the client, inspecting it and meeting up with it, and both tumbling and non-tumbling docking.
ELSA-d is the world’s first commercial demonstration debris removal mission.
UK Science Minister Amanda Solloway said: "The removal of hazardous space debris is not only environmentally important but is also a huge commercial opportunity for the UK, with companies like Astroscale leading the way in demonstrating how we can make space safer for everyone."
John Auburn, the managing director of Astroscale UK, said: "Our team is very proud to have developed the mission control and ground systems for ELSA-d.
"We will perform complex manoeuvres to demonstrate the release and capture of this debris, with the first semi-autonomous robotic magnetic capture of a piece of debris, tumbling through space, using advanced software and autonomous control technology."