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Anatomy of a debris incident

01 February 2017

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A space debris avoidance manoeuvre planned for ESA's Swarm mission proved unnecessary last week, but the close encounter highlighted the growing risk from space debris.

It's an increasingly common occurrence: ESA's Space Debris Office starts monitoring a piece of debris - there are over 22,000 tracked in space now - that could pass near one of the Agency's satellites.

Additional tracking data indicate the object - maybe a chunk of some old satellite already long abandoned - might pass too close, within the 'risk threshold' that surrounds each active spacecraft.

Upon closer look, uncertainty in the object's track combined with uncertainty in the satellite's orbit mean that a collision cannot be excluded. The only solution is for mission controllers to boost the satellite out of harms' way. It's time to take action.

This is exactly what happened on 24 January, when space debris experts at ESA's mission control centre in Darmstadt, Germany, alerted the Swarm flight control team that one of their three satellites, Swarm-B, would have a close call from a 15 cm chunk of the former Cosmos 375.

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