Naval Ocean Surveillance System

The Naval Ocean Surveillance System (NOSS) is a series of signals-intelligence satellites that have conducted electronic signals intelligence for the U.S. Navy since the early 1970s. The first series of satellites were codenamed "White Cloud" or "PARCAE", while second- and third-generation satellites have used the codenames "Ranger" and "Intruder".

Source: Wikipedia — Naval Ocean Surveillance System (CC BY-SA 4.0)