Science Pictures

SAR Radar Image

SAR¹ Radar Image of an area south of Avignon, France
(DEMR)

The spatial resolution of a radar antenna is inversely proportional to its size. The SAR (Synthetic Aperture Radar) technology makes use of the movement of the antenna to create a longer "synthetic" antenna, having therefore a higher spatial resolution than the one associated with same fixed antenna. The large antenna is reconstructed through signal processing.

The transmitting and receiving antennas are located on the same plane. They both are about ten centimeter long. The large "virtual" antenna used to produce the images displayed here is more than 60 meter long.

Each color corresponds to a particular polarization² pair, associated with the emitted wave and the receiving antenna, selected to characterize the interaction mechanism between the incident radar wave and the surface.

Maroon areas are mainly bare soils. Green areas are surfaces covered with vegetation.

Blue points indicate the presence of buildings or artificial structures.

The use of radar waves enables day/night and all-weather observation.

Glossary

1. Synthetic Aperture Radar (SAR)
   Radar technics exploiting the motion of a radar antenna to achieve an higher angular resolution than that of the motionless antenna. The angular resolution of an antenna is proportional to the inverse of its size which is limited aboard an aircraft (here, the antenna diameter is 4', thus providing a 1100 yards ground resolution, SAR processing increases the resolution to 1 yard).
2. Polarization
   The property of an electromagnetic wave which describes the direction of the electric field.

This is a mainly agricultural and natural zone,
except for the town of Montfavet at the center of the image.
The North is in the lower right corner of the image.

Last Update: July 1st, 2004 - © ONERA 2009 - Terms of use