Synthetic aperture radar

Synthetic aperture radar (SAR) combines radar echoes collected along a moving platform’s path to form images with the resolution of a much larger antenna.

Synthetic aperture: An effective antenna aperture synthesized by combining measurements taken from different positions along a platform’s path. SAR’s apparent long antenna is built computationally from the platform’s successive positions.
Radar: A system that uses reflected radio waves to detect objects and measure their range or motion. SAR is an imaging form of radar that exploits echoes rather than visible light.
Earth observation: The collection and analysis of information about Earth’s surface and atmosphere. SAR is a major source of imagery for mapping and monitoring Earth.
Real-aperture radar: Radar imaging whose spatial resolution is determined by the physical antenna beam and transmitted pulse. Unlike SAR, it does not synthesize a larger aperture through platform motion.
Remote sensing: The acquisition of information about objects or areas without physical contact. SAR broadened remote sensing with active microwave imaging that operates in darkness and through clouds.
Radar signal processing: Methods for extracting information from transmitted and received radar signals. SAR processing aligns echoes and focuses them into an image.
Electromagnetic wave: A wave of oscillating electric and magnetic fields that propagates through space. SAR transmits and receives radio-frequency electromagnetic waves.
Sentinel-1: A European Space Agency satellite mission carrying C-band synthetic aperture radar. Its freely available imagery supports routine land, ocean, and disaster monitoring.
Optical remote sensing: Remote sensing that measures reflected or emitted visible, infrared, or ultraviolet radiation. Optical images provide familiar spectral and visual detail but are impeded by clouds and darkness.
Earthquake remote sensing: The use of satellite and airborne observations to detect or characterize earthquake effects. SAR interferometry can map ground displacement across broad areas after earthquakes.

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