Real Aperture Radar (RAR)

A narrow beam of energy is directed perpendicularly to the flight path of the carrier platform (aircraft or spacecraft). A pulse of energy is transmitted from the radar antenna, and the relative intensity of the reflections is used to produce an image of a narrow strip of terrain.
Reflections from larger ranges arrive back at the radar after proportionately larger time, which becomes the range direction in the image. When the next pulse is transmitted, the radar will have moved forward a small distance and a slightly different strip of terrain will be imaged.

These sequential strips of terrain will then be recorded side by side to build up the azimuth direction. The image consists of the two dimensional data array.
In this figure, the strip of terrain to be imaged is from point A to point B. Point A being nearest to the nadir point is said to lie at near range and point B, being furthest, is said to lie at far range.

The distance between A and B defines the swath width. The distance between any point within the swath and the radar is called its slant range.
Ground range for any point within the swath is its distance from the nadir point (point on the ground directly underneath the radar).

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry