Editing Electronic warfare support measures

{{Short description|Electronic intelligence gathering method}}

[[File:Menwith-hill-radomes.jpg|thumb|right|[[RAF Menwith Hill]], a large [[ECHELON]] site in the [[United Kingdom]], and part of the [[UK-USA Security Agreement]].]]
[[File:Dupuy-de-Lome-photo10.jpg|thumb|French ship ''[[French ship Dupuy de Lôme (A759)|Dupuy de Lôme]]'', specialised in SIGINT]]

In military [[telecommunications]], '''electronic support''' ('''ES''') or '''electronic support measures''' ('''ESM''') gather intelligence through passive "listening" to electromagnetic radiations of military interest. They are an aspect of [[electronic warfare]] involving actions taken under direct control of an operational commander to detect, [[Signals intelligence|intercept]], identify, locate, record, and/or analyze sources of radiated electromagnetic energy for the purposes of immediate [[imminent threat|threat]] recognition (such as warning that [[fire control radar]] has locked on a combat vehicle, ship, or aircraft) or longer-term operational planning.<ref name="proceedings">Polmar, Norman "The U. S. Navy Electronic Warfare (Part 1)" ''United States Naval Institute Proceedings'' October 1979 p.137</ref>  Thus, electronic support provides a source of [[information]] required for decisions involving [[electronic protection]] (EP), [[electronic attack]] (EA), avoidance, targeting, and other tactical employment of forces. Electronic support [[data]] can be used to produce [[signals intelligence]] (SIGINT), [[COMINT|communications intelligence]] (COMINT) and [[electronics intelligence]] (ELINT).<ref>{{FS1037C}}</ref>

Electronic support measures can provide (1) initial detection or knowledge of foreign systems, (2) a library of technical and operational data on foreign systems, and (3) tactical combat information utilizing that library.<ref name="proceedings"/>  ESM collection platforms can remain electronically silent and detect and analyze RADAR transmissions beyond the RADAR detection range because of the greater power of the transmitted [[electromagnetic pulse]] with respect to a reflected echo of that pulse.<ref name="proceedings"/>  United States airborne ESM receivers are designated in the AN/ALR series.<ref name="proceedings"/>

Desirable characteristics for electromagnetic surveillance and collection equipment include (1) wide-spectrum or bandwidth capability because foreign frequencies are initially unknown, (2) wide dynamic range because the signal strength is initially unknown, (3) narrow bandpass to discriminate the signal of interest from other electromagnetic radiation on nearby frequencies, and (4) good angle-of arrival measurement for bearings to locate the transmitter.<ref name="proceedings"/>  The frequency spectrum of interest ranges from 30&nbsp;MHz to 50&nbsp;GHz.<ref name="proceedings"/>  Multiple receivers are typically required for surveillance of the entire spectrum,<ref name="proceedings"/> but tactical receivers may be functional within a specific signal strength threshold of a smaller frequency range.

== See also ==
* [[Airborne early warning and control|AWACS]]
* [[Boeing E-3 Sentry]]
* [[Boeing E-4]]
* [[Electronic warfare]]
** [[Electronic countermeasure]]
* [[Lockheed P-3 Orion|Lockheed Orion]]
* [[Low-probability-of-intercept radar]]
* [[MGARJS]]

== References ==
{{Reflist}}

[[Category:Military technology]]
[[Category:Military communications]]
[[Category:Electronic warfare]]


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