In this formation book, the reader will find a fresh and complete Synthetic Aperture Radar education. The multi decadal experience of Dr. Hellsten in studying, designing, testing, and operating the well-known Swedish low frequency SAR system Carabas has been condensed in a quite readable book. The mathematical competence of the author joint with his creative engineering experience accompanies the reader from the prime principles derivation of the Maxwell equations to say the design of the antennas, the evaluation of the attenuation due to a hedge of trees, the effects of Radio Frequency Interferences, the complete discussion of the effects on the scatter of vertical or horizontal polarization of the impinging waves, etc. etc. The methodologies to design the system are explained in detail, from the prime principles, as said, to the very efficient but complex SAR focusing technique known as Fast Factorized Back Projections, very well fit to accommodate airplane motion compensation. The reader is patiently accompanied through the complexities of the low frequency radar systems where the simple and approximate solutions that are well known do not apply, and everything has to be derived from the beginnings with mathematical precision: the scatterers are spheres and cylinders, not easy mirrors, at these frequencies likely to be too big to be feasible. The antenna gain is to be derived carefully and height and length are not enough: however, the mathematical tools are well explained and the reader is never left alone but always accompanied to the correct solution, as demonstrated by the experimental results. Finally, the reader has the correct impression to have been directed to command the field, as the author indeed does. In fact, the implementation of the system on helicopters and planes is also studied, as well as the effects of the scatter on an uneven and rough terrain. Finally, the effects on focusing of moving targets are discussed with precision, from the easy constant velocity case to the accelerated and random motion.
The author is to be deeply admired for his technical grasp, the clarity of the derivations, indeed always concise but nonetheless understandable and clear, and thanked for the masterful guidance of the readers through all the technical difficulties towards the commendable goal of an efficient and innovative system.