Inverse Synthetic Aperture Radar - ISAR Applications

ISAR Applications

ISAR is utilized in maritime surveillance for the classification of ships and other objects. In these applications the motion of the object due to wave action often plays a greater role than object rotation. For instance a feature which extends far over the surface of a ship such as a mast will provide a high sinusoidal response which is clearly identifiable in a two dimensional image. Images sometimes produce an uncanny similarity to a visual profile with the interesting effect that as the object rocks towards or away from the receiver the alternating doppler returns cause the profile to cycle between upright and inverted. ISAR for maritime surveillance was pioneered by Texas Instruments in collaboration with the Naval Research Laboratory and became an important capability of the P-3 Orion and the S-3B Viking US Navy aircraft.

Research has also been done with land based ISAR. The difficulty in utilizing this capability is that the object motion is far less in magnitude and usually less periodic than in the maritime case.

Perhaps the most visually striking and scientifically compelling application of ISAR is in the deep space imaging of asteroids. A particularly beautiful example of this is the so called "dog's bone" 216 Kleopatra asteroid, which lies roughly 20% further away from the earth than does the sun. The asteroid is only 60 miles wide at its midpoint. Yet the imagery is crisp and "feels" like an optical image. This has been cited as akin to using a Los Angeles telescope the size of the human eye's lens to image a car in New York. Of course the "trick" here is that the asteroid is presented amongst a very sparse background, allowing for substantial disambiguation.