Editing Signals intelligence (section)

==SIGINT and MASINT comparison==
{{Main|Measurement and signature intelligence}}
[[File:SAR-Lupe.jpg|thumb|A model of a German [[SAR-Lupe]] reconnaissance satellite inside a Soviet [[Cosmos-3M]] rocket.]]

Signals intelligence and measurement and signature intelligence (MASINT) are closely, and sometimes confusingly, related.<ref>{{cite web|last=Interagency OPSEC Support Staff (IOSS)|title=Operations Security Intelligence Threat Handbook: Section 2, Intelligence Collection Activities and Disciplines|date=May 1996|url=https://fas.org/irp/nsa/ioss/threat96/part03.htm|id=IOSS Section 2|access-date=3 October 2007}}</ref>
The signals intelligence disciplines of communications and electronic intelligence focus on the information in those signals themselves, as with COMINT detecting the speech in a voice communication or ELINT measuring the [[Radar signal characteristics|frequency, pulse repetition rate, and other characteristics]] of a radar.

MASINT also works with collected signals, but is more of an analysis discipline. There are, however, unique MASINT sensors, typically working in different regions or domains of the electromagnetic spectrum, such as infrared or magnetic fields. While NSA and other agencies have MASINT groups, the Central MASINT Office is in the [[Defense Intelligence Agency]] (DIA).

Where COMINT and ELINT focus on the intentionally transmitted part of the signal, MASINT focuses on unintentionally transmitted information. For example, a given radar antenna will have [[sidelobe]]s emanating from a direction other than that in which the main antenna is aimed. The RADINT (radar intelligence) discipline involves learning to recognize a radar both by its primary signal, captured by ELINT, and its sidelobes, perhaps captured by the main ELINT sensor, or, more likely, a sensor aimed at the sides of the radio antenna.

MASINT associated with COMINT might involve the detection of common background sounds expected with human voice communications. For example, if a given radio signal comes from a radio used in a tank, if the interceptor does not hear engine noise or higher voice frequency than the voice [[modulation]] usually uses, even though the voice conversation is meaningful, MASINT might suggest it is a deception, not coming from a real tank.

See [[HF/DF]] for a discussion of SIGINT-captured information with a MASINT flavor, such as determining the frequency to which a ''receiver'' is tuned, from detecting the frequency of the [[beat frequency oscillator]] of the [[superheterodyne receiver]].