25-01-2012, 04:15 PM
Introduction to Synthetic Aperture Radar
[attachment=16605]
GENERAL FACTS ABOUT SAR
Today, synthetic aperture radar (SAR) plays an important role in military ground surveillance and earth
observation. Since the late eighties a couple of SAR-systems have been developed for both space and
airborne operation. The underlying radar principle offers advantages compared to competing sensors in
infrared or visible spectral area.
Introduction to Synthetic Aperture Radar (SAR)
rain are impenetrable for this wavelength. Infrared sensors which are applicable day and night are even
more sensitive on weather conditions. Consequently, radar sensors represent a completion of the sensor
collection for remote sensing. Beyond the overall availability of SAR images there are further pros for the
utilization of radar. The coherent nature of SAR enables the user to process images of subsequent
overflights for interferometrical analyses. Depending on the radar wavelength the radar signal will be
reflected by vegetation or the ground structure.
Circumstances
It has been mentioned that the propagation and reflection of electromagnetic waves strongly depends on its
frequency. Figure 1 shows the atmospheric transmission for a wide frequency interval. SAR systems for
wide area surveillance have to operate in frequency areas with minimal attenuation. Beyond the Ka-band
only short range systems are realizable. Advantages of systems with a higher frequency are a reduced
system size and a simplified processing. X,- C- and L-band are very common for airborne and spaceborne
sensors.
