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Book Review:
Deep Space Flight and Communications:
Exploring the Sun as a Gravitational Lens

by Claudio Maccone
reviewed by H. Paul Shuch
Copyright © 2009
Springer-Praxis Books (Berlin)
ISBN 978-3-549-72942-6
401 pp

Most SETI League members are already familiar with the work of Dr. Claudio Maccone, through his regular presentations at various conferences. An advocate of gravitational lensing to dramatically increase the sensitivity of radio telescopes, and a passionate proponent of the adaptive Karhunen Loeve Transform (KLT) for SETI digital signal processing, Maccone was awarded the Giordano Bruno Memorial Award, the SETI League's highest technical honor, in 2002. Much of the material in his latest book was previously presented as papers at various SETICon, EuroSETI, and European Radio Astronomy Club meetings, as well as at annual International Astronautical Congresses around the globe. This textbook, however, is far from a collection of conference papers. It promises to be the seminal work in a newly emerging field of study.

The concept of gravitational lensing, long practiced by optical astronomers, is only recently being recognized as a signal amplifying technique for radio astronomical applications. Since the considerable mass of a star can focus incoming photons from distant sources, the result is a radio telescope of stellar proportions. Unfortunately, as Maccone shows in this book, in the case of our own Sun, those photons focus at a distance of 550 astronomical units and beyond. Thus, in order to use the Sun as an effective gravitational lens, one must launch radio receivers into solar orbit at greater than interplanetary distances. The mechanics of such a space mission are discussed in the present work, as are the communications challenges of commanding and controlling a spacecraft in the face of three-day one-way propagation times.

In addition to the astronautical challenges of such a mission, Maccone discusses the need for highly optimized, computationally intensive signal processing and analysis techniques. Not surprisingly since he expounded on its use in his doctoral dissertation decades ago, Maccone now advocates the KLT for this esoteric application, shows how it can improve SETI signal-to-noise ratio by three orders of magnitude as compared to the more conventional Fast Fourier Transform (FFT), and introduces improved algorithms to finally make its implementation feasible on available computational platforms. Finally, given the high velocities of relative motion involved for space missions to 550 AU and beyond, relativistic corrections become an important consideration, which Maccone explores in the present work.

Two decades in the making, Deep Space Flight and Communications is the result of merging two previously published, smaller books by the author. The first, The Sun as a Gravitational Lens: Proposed Space Missions, corresponds to Part I, and the second, Telecommunications, KLT and Relativity, corresponds to Part II of this revised and updated book. The extensive revision process has brought Maccone's two 20th Century works firmly into the 21st Century, and beyond.

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