Envisat — Europe’s 8-tonne derelict

On 8 April 2012, the European Space Agency abruptly lost contact with Envisat, then the largest civilian Earth-observation satellite ever flown. At roughly 8 tonnes, the spacecraft remains in a sun-synchronous orbit near 770 km — a heavily used altitude — with no propulsion control and no way to command it down.

One of the most-watched objects in orbit Because of its size and its position in a crowded orbital band, Envisat is considered one of the most significant single pieces of space debris. A collision involving an object that large would generate an enormous, long-lived debris cloud, so its conjunctions are tracked closely and it is a frequent candidate in studies of active debris removal — missions that would physically capture and deorbit large derelicts.

A symbol of the disposal problem Envisat predates today's stricter end-of-life disposal expectations. It will remain in orbit for roughly a century unless removed, making it a standing reminder of why modern missions are designed to deorbit themselves.