Related topics: nasa

Monitoring Earth's shifting land

The monitoring of land subsidence is of vital importance for low-lying countries, but also areas which are prone to peculiar ground instability.

Image: Antarctica detailed in 3-D

Unfortunately ice is a hot topic when it comes to understanding and monitoring how this fragile component of the Earth system is being affected by climate change. Scientists, therefore, go to great lengths to study changes ...

Scientists planning now for asteroid flyby a decade away

On April 13, 2029, a speck of light will streak across the sky, getting brighter and faster. At one point it will travel more than the width of the full Moon within a minute and it will get as bright as the stars in the Little ...

Cassini reveals surprises with Titan's lakes

On its final flyby of Saturn's largest moon in 2017, NASA's Cassini spacecraft gathered radar data revealing that the small liquid lakes in Titan's northern hemisphere are surprisingly deep, perched atop hills and filled ...

Where space missions are born

A high-resolution radar mission to Earth's 'evil twin' Venus, a spacecraft to detect the most powerful explosions in the Universe and an observatory for the cool, dusty cosmos to investigate the origins of stars: ESA's Concurrent ...

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Radar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for radio detection and ranging. The term has since entered the English language as a standard word, radar, losing the capitalization. Radar was originally called RDF (Radio Direction Finder, now used as a totally different device) in the United Kingdom.

A radar system has a transmitter that emits microwaves or radio waves. These waves are in phase when emitted, and when they come into contact with an object are scattered in all directions. The signal is thus partly reflected back and it has a slight change of wavelength (and thus frequency) if the target is moving. The receiver is usually, but not always, in the same location as the transmitter. Although the signal returned is usually very weak, the signal can be amplified through use of electronic techniques in the receiver and in the antenna configuration. This enables radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect. Radar is used in meteorological detection of precipitation, measuring ocean surface waves, air traffic control, police detection of speeding traffic, and by the military.

This text uses material from Wikipedia, licensed under CC BY-SA