Electro-optical MASINT is a subdiscipline of Measurement and Signature Intelligence, (MASINT) and refers to intelligence gathering activities which bring together disparate elements that do not fit within the definitions of Signals Intelligence (SIGINT), Imagery Intelligence (IMINT), or Human Intelligence (HUMINT).
Electro-optical MASINT has similarities to IMINT, but is distinct from it. IMINT's primary goal is to create a picture, composed of visual elements understandable to a trained user. Electro-optical MASINT helps validate that picture, so that, for example, the analyst can tell if an area of green is vegetation or camouflage paint. Electro-optical MASINT also generates information on phenomena that emit, absorb, or reflect electromagnetic energy in the infrared, visible light, or ultraviolet spectra, phenomena where a "picture" is less important than the amount or type of energy reported. For example, a class of satellites, originally intended to give early warning of rocket launches based on the heat of their exhaust, reports energy wavelengths and strength as a function of location(s). There would be no value, in this specific context, to seeing a photograph of the flames coming out of the rocket.
Subsequently, when the geometry between the rocket exhaust and the sensor permits a clear view of the exhaust, IMINT would give a visual or infrared picture of its shape, while electro-optical MASINT would give, either as a list of coordinates with characteristics, or a "false-color" image, the temperature distribution, and spectroscopic information on its composition.
In other words, MASINT may give warning before characteristics visible to IMINT are clear, or it may help validate or understand the pictures taken by IMINT.
MASINT techniques are not limited to the United States, but the U.S. distinguishes MASINT sensors from others more than do other nations. According to the United States Department of Defense, MASINT is technically derived intelligence (excluding traditional imagery IMINT and signals intelligence SIGINT) that – when collected, processed, and analyzed by dedicated MASINT systems – results in intelligence that detects, tracks, identifies, or describes the signatures (distinctive characteristics) of fixed or dynamic target sources. MASINT was recognized as a formal intelligence discipline in 1986. Another way to describe MASINT is "a 'non-literal' discipline. It feeds on a target's unintended emissive byproducts, the 'trails' of thermal energy, chemical or radio frequency emission that an object leaves in its wake. These trails form distinct signatures, which can be exploited as reliable discriminators to characterize specific events or disclose hidden targets".
As with many branches of MASINT, specific techniques may overlap with the six major conceptual disciplines of MASINT defined by the Center for MASINT Studies and Research, which divides MASINT into Electro-optical, Nuclear, Geophysical, Radar, Materials, and Radiofrequency disciplines.
MASINT collection technologies in this area use radar, lasers, staring arrays in the infrared and visual, to point sensors at the information of interest. As opposed to IMINT, MASINT electro-optical sensors do not create pictures. Instead, they would indicate the coordinates, intensity, and spectral characteristics of a light source, such as a rocket engine, or a missile reentry vehicle. Electro-optical MASINT involves obtaining information from emitted or reflected energy, across the wavelengths of infrared, visible, and ultraviolet light. Electro-optical techniques include measurement of the radiant intensities, dynamic motion, and the materials composition of a target. These measurements put the target in spectral and spatial contexts. Sensors used in electro-optical MASINT include radiometers, spectrometers, non-literal imaging systems, lasers, or laser radar (LIDAR).
Observation of foreign missile tests, for example, make extensive use of MASINT along with other disciplines. For example, electro-optical and radar tracking establish trajectory, speed, and other flight characteristics that can be used to validate the TELINT telemetry intelligence being received by SIGINT sensors. Electro-optical sensors, which guide radars, operate on aircraft, ground stations, and ships.
Read more about Electro-optical MASINT: Airborne Electro-optical Missile Tracking MASINT, Tactical Counter-artillery Sensors, Infrared MASINT, Optical Measurement of Nuclear Explosions, Laser MASINT, Spectroscopic MASINT, Space-based Staring Infrared Sensors, Shallow Water Operations