'Magnetic space tug could target dead satellites'

Derelict satellites could in future be grappled and removed from key orbits around the Earth with a space tug using magnetic forces, scientists say.
This same magnetic attraction or repulsion is also being considered as a safe method for multiple satellites to maintain close formations in space, researchers said.
Such satellite swarms are being considered for future astronomy or Earth-observing missions - if their relative positions can stay stable they could act as a single giant telescope.
To combat space debris, interest is growing in plucking entire satellites from space. The biggest challenge is to grapple and secure such uncontrolled, rapidly tumbling objects, typically of several tonnes.

Multiple techniques are being investigated, including robotic arms, nets and harpoons.
"With a satellite you want to deorbit, it is much better if you can stay at a safe distance, without needing to come into direct contact and risking damage to both chaser and target satellites," said Emilien Fabacher from the University of Toulouse in France.

"So the idea I am investigating is to apply magnetic forces either to attract or repel the target satellite, to shift its orbit or deorbit it entirely," said Fabacher.
Such target satellites would not need to be specially equipped in advance.
Instead, such a tug would influence target satellites using their 'magnetorquers': reliable electromagnets already carried to adjust orientation using Earth's magnetic field.

The strong magnetic field required by the chaser satellite would be generated using superconducting wires cooled to cryogenic temperatures.
Similarly satellites could also keep multiple satellites flying in precise formation, said Finn Ankersen, an ESA expert in formation flight, rendezvous and docking.