TABLE OF CONTENTS Electronic support (ES) was previously called electromagnetic support measures (ESM) and is still often called by that name. It is the listening part of EW. ES systems and subsystems detect threat signals and display the types and location of transmitters to support situation awareness or cue electronic attack capabilities.
The primary ES functions are detection of threat signals, identification of threat types and operating modes, location of threat emitters, specific emitter identification (SEI), and display or handoff of threat information. The most important ES system types are radar warning receivers (RWRs), threat-targeting systems (often called ESM systems), and battlefield surveillance systems.
ES systems operate in both the radar and communication bands, providing similar functions. However, the nature of the signals dictates different approaches. There are also differences in the way tasks are approached for airborne, ground-based, and shipboard applications.
The purpose of an RWR is to identify the presence of threats to an aircraft quickly so that countermeasures or maneuvers can be taken to defeat the impending attack. An RWR is designed to operate in a high-density signal environment. It can typically accept millions of pulses per second along with CW radars. It is usually required to identify and report new threats within approximately one second.
The RWR, by identifying threat radars, determines each actual threat that is present. This will be a particular type of surface-to-air missile (SAM), Radar-controlled antiaircraft gun (AAA), or fighter aircraft with aerial intercept (AI) radar.
