Remote sensing is the technology behind gathering information from a distance, typically through electro-optical instruments carried by aircraft or satellites. The data is collected through detection of energy reflected from the Earth.
Sensors are either active or passive. Passive instruments respond to external conditions, such as radiated heat (infrared) or reflected sunlight. Active sensors use some form of internal stimuli, usually radio frequencies or lasers which can be bounced off a target. The return signal is analyzed to determine distance, size, and other characteristics.
Remote sensor devices in use include radiometric and spectroradiometric devices. These instruments measure the energy emission of objects as a function of wavelength over time, and require precise calibration in radiometric units. Filters for reducing interference are also typically a part of any design to assure more accurate readings.
Remote systems are an important monitoring tool in many applications. It can be used for geologic data such as mapping, weather patterns, erosion, and coastal changes. Marine applications include tracking water temperatures, currents, wave patterns, and the distribution of sea ice. It often serves as an early warning system in the case of disasters such as hurricanes, floods, and forest fires. In military and law enforcement, it can help in locating and tracking enemy or criminal personnel, locations, and resources, in addition to guiding first responders to emergencies.
The term “fog of war” refers to the state of confusion which can impede operations, due to confusion from a lack of information on enemy movements, terrain, or weather. This is becoming less of a problem for modern leaders who can rely on accurate and often highly detailed data obtained from remote sensor systems.
Military and crisis management situations are focused not just on improved technology, but integrating sensors with computers and networking devices. The coordination or synergy between these assets can allow for automated logging and alerts, faster analysis, and creating recordings or predictive models for training and further investigation. Remote sensing operations in use today include JSTARS (Joint Surveillance Targeting Attack Radar System), Global HAWK, and a new generation of high-altitude planes which can help coordinate widespread activities in a network-based system.
Modern military systems for remote observation have been in use with varying levels of success since the first Gulf War, but today can accurately guide entire armies or single drones or missiles to a target in a variety of weather and lighting conditions.
Remote sensing is also an indispensable tool for units such as the Coast Guard or National Guard who are often called upon in crisis situations to provide support, rescue imperiled civilians, or enforce laws, and to scientific research so essential to further progress.