Microwave remote sensing is a main area of research of the German Aerospace Research Establishment (DLR). Especially the Institut fuer Hochfrequenztechnik is engaged in this field by making use of synthetic aperture radar systems (SAR) on both air- and spaceborne platforms. The institute's engagement in the international projects ERS-1 and SIR-C/X-SAR initiated the design and development work, which lead to the well-known Experimental airborne SAR, E-SAR. It is used for testing new technologies and signal processing algorithms. In recent years it has advanced to a main research tool for remote sensing applications in geology, agriculture, forestry and military reconnaissance.