E-SAR is an experimental Synthetic Aperture Radar (SAR) System on board the Dornier DO-228 research aircraft of the German Aerospace Center (DLR).
It basically consists of a radar system which provides high resolution images of the terrain it flys over. There are a number of advantages compared with optical systems like a camera. Images of the ground below can be recorded independently of the time of day or the weather. The principle is based on sending out a radar signal which, because of its frequency, polarization and angle of ground impact, is reflected back. Part of this reflected signal returns to the radar system and is recorded there. What the reflected signal is like depends on the ground from which it was reflected. Moisture and ground cover, whether pastures, forests, fields or human settlements, and in the latter case whether we are dealing with streets, buildings or entire cities, influence the reflected signal, which thus contains this information.
On the ground the recorded return signals are processed in a computer to form an image. In this way agricultural and forestry maps can be generated; even topographical maps with elevation information can be produced with SAR systems.
The SAR system is operated by the Microwaves and Radar Institute together with DLR's Flight Department in Oberpfaffenhofen.