ELISA 1, ELISA 2, ELISA 3 and ELISA 4 (Electronic Intelligence by Satellite) are a suite of French military satellites launched on 17 December 2011 from Arianespace's Kourou spaceport in French Guiana.
The ELISA suite are microsatellites and thus all four were launched on a single Soyuz ST-B rocket, along with Pleiades-1 and SSOT. The ELISA programme is a demonstration system to pave the way for a planned radar monitoring system called CERES. The ELISA satellites are in a Low Earth orbit a few kilometres from each other to record radar and radio transmissions. Since 2014, they are used as a pre-operational system.
The satellites are built around the Myriade micro-satellite bus.
References
ELISA (satellite) Wikipedia(Text) CC BY-SA