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The dipole antenna of a radar altimeter of 1947. A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it takes a beam of radio waves to travel to ground, reflect, and return to the craft.
Radar altimeter technology is also used in terrain-following radar allowing combat aircraft to fly at very low height above the terrain. After extensive research and experimentation, it has been shown that "phase radio-altimeters" are most suitable for ground effect vehicles , as compared to laser, isotropic or ultrasonic altimeters.
The radar mile is the time it takes for a radar pulse to travel one nautical mile, reflect off a target, and return to the radar antenna. Since a nautical mile is defined as 1,852 m, then dividing this distance by the speed of light (299,792,458 m/s), and then multiplying the result by 2 yields a result of 12.36 μs in duration.
Pages in category "Earth satellite radar altimeters" The following 19 pages are in this category, out of 19 total. This list may not reflect recent changes. C.
A radar altimeter uses the round-trip flight-time of a microwave pulse between the satellite and the Earth's surface to determine the distance between the spacecraft and the surface. From this distance or height, the local surface effects such as tides, winds and currents are removed to obtain the satellite height above the geoid.
A conventional nadir radar altimeter will also be flown, and measure just beneath the satellite, as was done on the Topex/Poseidon, Jason series, and SARAL missions. It is a "Jason-class" altimeter. It is a "Jason-class" altimeter.
Radar echoes, showing a representation of the carrier. Pulse width also determines the radar's dead zone at close ranges. While the radar transmitter is active, the receiver input is blanked to avoid the amplifiers being swamped (saturated) or, (more likely), damaged.
The missile's radar altimeter feeds measurements into a small buffer that periodically "gates" the measurements over a period of time and averages them out to produce a single measurement. The series of such numbers held in the buffer produce a strip of measurements similar to those held in the maps.