To See the Unseen: A History of Planetary Radar Astronomy (review)

Radar astronomy has played an important role in solar system research ever since it grew out of the development of radar during World War II. Ever more powerful radars and sensitive receivers were employed to bounce radar off the moon (first done in 1946), nearby planets (early 1960s), asteroids (1968), the rings of Saturn (1973), the moons of Jupiter (1974), and comets (1980). By the mid-1960s the earth-sun distance had been measured to unprecedented accuracy (149,600,000 ±1,000 km), and general relativity had “passed” a fourth important test (the time-delay test of Irwin Shapiro). As computer power grew, improved signal analysis techniques allowed increasingly detailed mapping of planetary surfaces. In the end, the radar technique was itself launched into space, and two National Aeronautics and Space Administration (NASA) missions to cloud-shrouded Venus (Pioneer Venus in 1980 and Magellan in 1990) masterfully mapped out its previously hidden topography.

In To See the Unseen, Andrew Butrica lays out this history in a thoroughly researched volume written under contract to NASA. The emphasis is on institutional and administrative history rather than on science and engineering. Through interviews with the participants and extensive archival digging, Butrica tells the story of how radar astronomy always remained a “little science,” albeit closely allied with, and dependent on, the “big equipment” (and big budgets) of “big sciences” such as space science, radio astronomy, and ionospheric research. Radar astronomy remained “little” as gauged by the number of publishing participants (peaking at only a few dozen in the 1960s), the investment in equipment, and the field’s secondary status at its leading institutions such as the Jet Propulsion Lab, Jodrell Bank, Arecibo Observatory, and the Massachusetts Institute of Technology’s Lincoln Labs. Although Butrica does not ignore developments in England and the Soviet Union, the book focuses on the American scene, where most radar astronomy has always been conducted. In the United States, radar astronomy was done “as an aside” using NASA spacecraft-tracking antennae (at Goldstone, California) and cold war technology, such as the distant early warning (DEW) missile-warning radar system, the ballistic missile early warning system (BMEWS), or the Arecibo 1,000-foot dish.

The book is annoyingly dense, both in terms of words per square inch (seven lines per inch for the main text and nine for the footnotes) and viscous style. A typical example: “Harry Messel, head of the University of Sydney School of Physics and joint director, with Gold, of the Cornell-Sydney University Astronomy Center, protested to Donald F. Hornig, the special presidential assistant for science and technology, that any change in the AO management structure would affect the Cornell-Sydney arrangement, too” (p. 99). Unfortunately, the writing rarely captures the excitement of the chase or, what is vital for any good history, the uncertainty, at any given time, of the future. The index is erratic, the abbreviated citations in footnotes frustrating (for instance, referring to a citation one hundred pages earlier and now impossible to find), and the layout of illustrations amateurish (frequent, large blank spaces).

If you have an interest in topics that bear on radar astronomy and its milieu over the past half-century, then you should read this book, for it is the only overview that exists and is full of intricate detail. Butrica has obviously done good research and organized it into a coherent story, but his attempts at a broader interpretation often go astray. One case involves his argument that planetary radar astronomy dealt with two classes of problems: those related to the distances, orbits, and rotation rates of planets (dynamics), and those concerned with deriving maps of the physical properties of planetary surfaces. The first he calls “science,” and the second “engineering”; the second (alone) are also called epistemological in nature. But these distinctions are not justified at all, nor could they be. Both types of...