Although it originated in the 1930s, radio astronomy reached maturity during the latter half of the 20th century. One of the major sites of radio astronomy during that period was the US National Radio Astronomy Observatory (NRAO). In Open Skies: The National Radio Astronomy Observatory and Its Impact on US Radio Astronomy, Kenneth Kellermann, Ellen Bouton, and Sierra Brandt tell the story of that august institution, warts and all: from the NRAO’s genesis in the mind of NSF’s first director, Alan Waterman; through the growing pains it faced during its early years; to its current status as a world-class radio astronomical facility.
To minimize interference in the radio spectrum, the National Radio Astronomy Observatory employs a fleet of electronics-free vintage cars, such as the Checker Marathon pictured here, for site maintenance.
To minimize interference in the radio spectrum, the National Radio Astronomy Observatory employs a fleet of electronics-free vintage cars, such as the Checker Marathon pictured here, for site maintenance.
A weighty tome of over 600 pages, the book begins with three chapters describing the early history of radio astronomy before delving into the NRAO’s history in chapter 4. In that section, the authors introduce us to the first radio telescope erected at the NRAO’s site in Green Bank, West Virginia: a 30 MHz interferometer that saw first light a year before the Green Bank site officially opened in October 1957.
From the start, the plan was to erect 85-foot and 140-foot radio telescopes at Green Bank. But a turf war quickly broke out between two committees involved with the observatory’s design. Even after they agreed on the size of the larger telescope—140 feet—there were heated arguments about the type of mounting to be used and the surface accuracy of the parabola. Construction of the 140-foot telescope wasn’t finished until 1965, five years later than planned.
While that project was stalled, the NRAO managed to secure about $1 million in funding from NSF for a simple 300-foot radio telescope with an inexpensive altazimuth mounting. Funding was approved in 1961, and in record time the 300-foot telescope was finished. The NRAO finally was an international-class radio astronomical facility.
Given the focus on instrumentation, people, and politics, Open Skies contains little discussion of the major research accomplishments of the NRAO and its staff. Nevertheless, the authors highlight a few examples of scientific discoveries made at Green Bank, including supernova remnants, planetary nebulae, radio galaxies, and quasars. They also discuss the discovery of radio recombination lines and interstellar molecules.
Perhaps the most famous NRAO instrument is the Very Large Array (VLA), discussed in chapter 7. It comprises 27 mobile parabolas, each 25 meters in diameter, which are arranged in a Y-shape at a radio-quiet site outside Socorro, New Mexico. Construction of the VLA began in late 1972, and in July 1980—18 years after it was first proposed—the VLA was fully operational. It was not only the most powerful radio telescope in the world but also the most complex one ever built.
Another area of radio astronomy for which the NRAO is justly famous is very long baseline interferometry (discussed in chapter 8), which involves electronically linking separate radio telescopes located across Earth, and even in space, to achieve resolutions that greatly exceed those possible using optical telescopes. Canadian and US radio astronomers (including Kellermann) were the early pioneers in that exciting new field.
Although the NRAO had from its founding intended to acquire a very large antenna, after the 140-foot debacle they couldn’t find support for such a program. But on 15 November 1988, the 300-foot telescope at Green Bank suddenly collapsed—fortunately with no loss of life. Senator Robert Byrd of West Virginia used the collapse, which the media described as a disaster, to lobby successfully for a replacement antenna. The result was a new 100-meter radio telescope, called the Green Bank Telescope, whose story is related in chapter 9.
Chapter 10 describes the NRAO’s first telescope dedicated to millimeter-wave radio astronomy, a 36-foot parabola sited in a dome at Kitt Peak National Observatory near Tucson, Arizona. It practically single-handedly gave rise to the field of astrochemistry. That chapter also discusses the NRAO’s role in the planning of the internationally run Atacama Large Millimeter/Submillimeter Array in Chile.
The final chapter in the book covers the NRAO’s contributions to 21st-century radio astronomy. It offers reflections on the love-hate relationship between the NRAO and university-based radio astronomy programs, the philosophical differences between the NRAO and optical astronomers at the Kitt Peak National Observatory, patterns of conflict and collaboration in US radio astronomy, and the management of frequency spectra. The authors round out the book by discussing the most ambitious international radio astronomy project ever devised: the Square Kilometre Array, currently under construction in Africa and Australia.
Well researched and well illustrated, Open Skies contains copious references at the end of each chapter for those wanting to learn more. It is also an open-access book, which means that the digital edition is freely available for anyone to download and read. Although it focuses on the US, Open Skies places the NRAO’s achievements in both a domestic and an international context. For those wanting to know about the development of post– World War II radio astronomy—and not just about the NRAO—Open Skies is essential reading.
Wayne Orchiston is an astronomer and historian of astronomy. He is the former president of the International Astronomical Union’s commission on the history of astronomy. His research focuses mainly on southeast Asia and on the international history of radio astronomy.
