Essaim (satellite)

Essaim (swarm, in French) is a French military reconnaissance microsatellite constellation. Its main purpose is to collect and map signals intelligence across the world. The DGA describes it as a "vacuum cleaner for [radio] waves".

Description
Essaim is a constellation of four 120 kg micro satellites (including one spare) in low earth orbit. They are demonstration models which were supposed to last three years. They fly separated by a few hundreds of kilometers. Missions are designed by the Celar (Centre d'électronique de l'armement) in Bruz, near Rennes and are uploaded from CNES in Toulouse to the constellation. Collected data follows the same path in reverse order.

Launch
The constellation was launched from Kourou, in French Guyana, by an Ariane 5 G+ rocket on December 18, 2004. The flight was shared with Helios 2A and two other auxiliary payloads: Parasol and Nanosat. Individual members of the constellation are Essaim 1, Essaim 2, Essaim 3 and Essaim 4.

Decommissioning
ESSAIM disposal and passivation operations took place in October 2010. The satellites are expected to reenter within 15 to 19 years.