Swarm Spacecraft Dodges Collision With Space Junk During Climb To Escape Sun’s

Artist’s view of Swarm, ESA’s first Earth observation constellation of satellites. Credit: ESA–P. Carril, 2013

The pressure is rising at ESA’s mission control. A European Space Agency (ESA) satellite dodges out of the way of a mystery piece of space junk that was spotted just hours before a potential collision.

This means a vital step in the spacecraft’s ongoing journey to safer skies now has to be quickly rescheduled, as violent solar activity related to the ramping up of the solar cycle warps Earth’s atmosphere and threatens to drag the satellite down out of orbit…

A swarm? Of bugs?

Not quite – Swarm is actually ESA’s mission to unravel the mysteries of Earth’s magnetic field. It’s comprised of three satellites, A, B, and C – affectionately known as Alpha, Bravo, and Charlie.

What happened?

A small piece of human-made junk circling our planet – known as space debris – was detected hurtling towards Alpha at 16:00 CEST (10:00 a.m. EDT), on June 30. From the trajectory, a potential collision was predicted just eight hours later, shortly after midnight. The chance of impact was great enough that Alpha needed to get out of the way – fast.

Swarm constellation. Swarm is ESA’s first Earth observation constellation of satellites. Its mission is to unravel one of the most mysterious aspects of our planet: the magnetic field. Credit: ESA–P. Carril, 2013

There’s junk in space?

A lot of it. Rocket parts, old satellites, and small pieces of debris left over from previous collisions and messy breakups orbit our planet. Each little piece can cause serious damage to a satellite, while larger ones can destroy a satellite and create a large amount of new debris.

Was this the first time this has happened?

That day? Maybe. Ever? No way. Each one of ESA’s satellites has to perform on average two evasive maneuvers every year – and that’s not including all the alerts they get that don’t end up needing evasive action.

The picture shows Sentinel-1A’s solar array before and after the impact of a millimetre-size particle on the second panel. The damaged area has a diameter of about 40 cm, which is consistent on this structure with the impact of a fragment of less than 5 millimeters in size. Credit ESA

Then what’s the big deal?

Carrying out evasive action – known as a ‘collision avoidance maneuver’ – requires a lot of planning. You have to check that you’re not moving the satellite into a new orbit that puts it at risk of other collisions and you have to calculate how to get back to your original orbit using as little fuel and losing as little science data as possible.

ESA’s Space Debris Office analyses data from the US Space Surveillance Network and raises the warning of a potential collision to ESA’s Flight Control and Flight Dynamics teams, usually more than 24 hours before the piece of debris comes closest to the satellite.

In this case, we only got eight hours’ notice.

And worse, the alert meant that the Swarm team was now suddenly racing against two clocks. Another maneuver was planned for just a few hours after the potential collision and had to be canceled to give Alpha enough time to duck out of the way of the…