CT: Radar is an acronym for “radio detection and ranging.” A radar system usually operates in the ultra-high-frequency (UHF) or microwave part of the radio-frequency (RF) spectrum, and is used to detect the position and/or movement of objects. Radar can track storm systems, because precipitation reflects electromagnetic fields at certain frequencies. Radar can also render precise maps. Radar systems are widely used in air-traffic control, aircraft navigation, and marine navigation.
High-power radar, using large dish antennas, has been used to measure distances to the moon, other planets, asteroids, and artificial satellites. From unmanned spaceprobes, radar has been used to map Venus, whose surface is obscured at visible wave lengths by a thick layer of clouds. Radar has been employed by NASA(the U.S. National Aeronautics and Space Administration) to make highly detailed topographical maps of the earth’s surface as well.
S: SMB – https://bit.ly/2rzIcQH (last access: 13 December 2018)
N: 1. “Electronic system for locating objects by means of radio waves,” 1941, acronym (more or less) from radio detecting and ranging. The U.S. choice, it won out over British radiolocation. Figurative from 1950.
2. RADAR stands for RAdio Detecting And Ranging, a device or system consisting usually of a synchronized radio transmitter and receiver that emits radio waves and processes their reflections for display and is used especially for detecting and locating objects (such as aircraft) or surface features (as of a planet).
3. The electronic principle on which radar operates is very similar to the principle of sound-wave reflection. If you shout in the direction of a sound-reflecting object (like a rocky canyon or cave), you will hear an echo. If you know the speed of sound in air, you can then estimate the distance and general direction of the object. The time required for an echo to return can be roughly converted to distance if the speed of sound is known. Radar uses electromagnetic energy pulses in much the same way. The radio-frequency (rf) energy is transmitted to and reflected from the reflecting object. A small portion of the reflected energy returns to the radar set. This returned energy is called an ECHO, just as it is in sound terminology. Radar sets use the echo to determine the direction and distance of the reflecting object.
4. Radar classifications:
- Based on specific function: primary radar, secondary radar, pulse radar, and continuous wave radar.
- Based on scan patterns: conical scan, Track-While-Scan(TWS) radars, monopulse scan radars, electronic scanning radars.
- Based on applications: air traffic management radars, air-defence radars, tracking radars, meteorological radars, imaging radars.
5. In the fields of Radar, Radio Guidance and Goniometry, Remote Sensing and Air Navigation Aids:
- A system using beamed and reflected radio-frequency energy for detecting and locating objects, measuring distance or altitude, navigating, homing, bombing and other purposes.
- In detecting and ranging, the time interval between transmission of the energy and the reception of the reflected energy establishes the range of an object in the beam’s path.
- The term radar is derived from “radio detection” and “ranging.”
- There are two types of radar: primary surveillance radar (PSR) and secondary surveillance radar (SSR).
- radar: term standardized by the Glossary for Pilots and Air Traffic Services Personnel Committee and officially approved by the RADARSAT-2 Terminology Approval Group (RTAG) in Canada.
6. It is important not to confuse sonar and radar, although both are remote sensing systems with important military, scientific and commercial applications. They rely on two fundamentally different types of wave transmission. Radar sends out electromagnetic waves, while active sonar transmits acoustic (i.e., sound) waves. In both systems, these waves return echoes from certain features or targets that allow the determination of important properties and attributes of the target (i.e., shape, size, speed, distance, etc.). Because electromagnetic waves are strongly attenuated (diminished) in water, radar signals are mostly used for ground or atmospheric observations. Because SONAR signals easily penetrate water, they are ideal for navigation and measurement under water.
S: 1. OED – https://bit.ly/2PzYNgv (last access: 12 December 2018). 2. AUGOV – https://bit.ly/2ErqPtC (last access: 12 December 2018); MW – https://bit.ly/2Gcqqgh (last access: 12 December 2018). 3. RadarTutorial – https://bit.ly/2ry8Rxh (last access: 12 December 2018). 4. EngineersGarage – https://bit.ly/2EfeLee (last access: 12 December 2018). 5. TERMIUM PLUS – https://bit.ly/2LgUIxb (last access: 13 December 2018). 6. ENCY – https://bit.ly/2PNj9Dq (last access: 17 December 2018).