Relationship between ESM and SIGINT

The functions of search, intercept, location and analysis are common to both ESM and SIGINT operations. ESM and SIGINT operations are conducted before and during hostilities and can be practised during military exercises. Differences arise in purpose and employment of these functions and the use of the derived information. The purposes, for which operations are performed, and the techniques used to carry them out, are to be the basic criteria for determining whether they are to be described as EW (ESM) or SIGINT operations. There must be close coordination between ESM and SIGINT operations, particularly when separate assets are employed, to ensure duplication of effort or conflict of interests is avoided.

ESM provides information for the conduct of EW activities and tactical actions such as avoidance, targeting and locating. It is also a source of information for local EOB preparation, surveillance and EW mission control. ESM provides intercept, identification and location of hostile, friendly and neutral emissions using equipment and techniques that can be the same or similar to those used by SIGINT and may draw on databases produced by SIGINT activities and other intelligence sources.
SIGINT provides intelligence support for users at all levels, from national governments to military commanders, and for purposes ranging from long term planning to direct timely support for combat operations, including EW operations. SIGINT can provide time critical information and the technical data and intelligence necessary to develop equipment and procedures for the conduct of EW operations. SIGINT support to military operations may be provided by assets organic to the supported commander or by tasked national level assets.
In SIGINT operations and, to a slightly lesser degree in ESM operations, there is a need to protect sources and methods of collecting information. It is essential, therefore that national and military level policy exists to ensure that information derived from SIGINT and ESM can be used in a timely manner whilst safeguarding national interests.
Although SIGINT is a national asset there should be policies and procedures in place that allow timely information exchanges during Combined operations. It is now normal practice to establish a National Intelligence Cell (NIC), which includes a SIGINT Section, within the Joint Force HQ on Combined operations. The NIC will normally sit under the control of J2 and close co-ordination and liaison with the EWCC is essential to ensure that EW and SIGINT provide mutual support at the National and International levels.