Selex ES was a subsidiary of Finmeccanica, active in the electronics and information technology business, based in Italy and the UK, and formed in January 2013, following Finmeccanica's decision to combine its existing SELEX Elsag and SELEX Sistemi Integrati businesses into SELEX Galileo, the immediate predecessor of Selex ES. From 1 January 2016, the activities of Selex ES merged into Leonardo-Finmeccanica's Electronics, Defence and Security Systems Sector becoming Leonardo S.p.A.

Passive radar is a class of radar systems that detect and track objects by processing reflections from non-cooperative sources of illumination in the environment, such as commercial broadcast and communications signals. It is a specific case of bistatic radar – passive bistatic radar (PBR) – which is a broad type also including the exploitation of cooperative and non-cooperative radar transmitters.