The accumulated junk ranges in nature from big rocket segments through to tiny shards of metal that have been created in accidental explosions and collisions. All move with high velocity and are therefore capable of destroying, or at least badly damaging an active satellite, of which there are currently over 3,000.
Precise tracking is possible on debris objects larger than 10cm. There are about 30,000 of these in the catalogue, but there may be one million items out there nearer to 1cm in size that are extremely difficult to monitor.
Spacecraft owners are asked to adhere to guidelines that would see all their retired missions brought out of the sky within 25 years of the end of operations. But compliance is poor, and experts agree we now need to start fetching the bigger pieces of junk and bringing them down - if we want near-Earth orbits to remain useable.
Astroscale wants to offer this as a commercial service.
"In the same way that you call up a breakdown service when your car breaks down on the motorway, the idea is that we can do the exact same thing for space - a space sweeping service which can clean up as we go," said Harriet Brettle, the head of business analysis at Astroscale.
On the design board for future commercial missions is an Elsa-M mission, where the M stands for "multi-client'. In this scenario, the servicer would capture in turn three clients and pull them down into lower orbits where they could more easily re-enter the atmosphere and burn up.
The client spacecraft, or mouse, for this Astroscale demo was manufactured by Surrey Satellite Technology Limited (SSTL) of Guildford.
Two other British-made satellites joined the ride to orbit, both manufactured by Open Cosmos on the Harwell science campus in Oxfordshire - the same location as for Astroscale's mission operations centre.
One of the Open Cosmos platforms is to be used by Lacuna Space, again based at the Harwell Hub. Lacuna is developing an "Internet of Things" (IoT) constellation of small satellites that can link dispersed connected objects on the ground - everything from shipping containers to migrating animals.