sar

SAR is an acronym used in several unrelated fields. The most common referents are Synthetic Aperture Radar, Search and Rescue, and Specific Absorption Rate.

Synthetic Aperture Radar (SAR) is a radar technique that produces high-resolution images from moving platforms. By collecting echoes as the platform moves, it synthesizes a large aperture, yielding finer detail than a static radar. It works day or night and through clouds, using microwave radiation. Common modes include stripmap and spotlight; Interferometric SAR (InSAR) measures surface deformation. Applications include earth observation, mapping, natural-hazard monitoring, forestry, and surveillance.

Search and Rescue (SAR) refers to operations that locate and assist people or vessels in distress. It involves coordination among agencies and volunteers, and uses planned search patterns, aircraft and ground teams, and technologies such as EPIRBs, PLBs, ELTs, radios, thermal imaging, and drones. Timely alerts and effective communication are critical to successful outcomes, and SAR missions may be conducted at local, national, or international levels.

Specific Absorption Rate (SAR) is the rate at which the body absorbs energy from an electromagnetic field, expressed in watts per kilogram. Regulatory limits prevent excessive heating; for example, the United States permits up to 1.6 W/kg averaged over 1 gram of tissue, while many European standards set 2.0 W/kg averaged over 10 grams. Devices are tested to comply with these limits according to ICNIRP and national regulators.

Because SAR has multiple meanings, context determines which concept is being referred to.