Synthetic array radar

The article discusses radar imaging or synthetic array radar (SAR). The most obvious advantage of SAR mapping is that it is all-weather. Radio waves can generally penetrate clouds, fog, and haze; so mapping is not hampered by atmospheric conditions. However, if the rain is heavy enough, the radar signal can to some extent indicate how hard it is raining. Since radar provides its own illumination, maps can be made night or day. Moreover, when mapping with radar, both the angle and the direction of the illumination can be changed. As with visual and infrared systems, when carried in a satellite, an SAR can map large areas in a very short time. SAR has even more advantages. Since it can sense distance as well as angle, it can map in three dimensions. This radar system represents a major technological step forward for spaceborne radar observations. The pictures in this article were collected during two space shuttle flights in April and October 1994. These two flights sampled the same sites during two different seasons to study the Earth's ecosystems, climatic and geological processes, the water cycle and ocean circulation.