Open Skies: The National Radio Astronomy Observatory and Its Impact on US Radio Astronomy

by Kenneth I. Kellermann, Ellen N. Bouton and Sierra S. Brandt

We dedicate the book to the memory of Dave Heeschen, whose wise and forceful leadership and commitment to Open Skies led NRAO to become the world’s premier radio astronomy observatory.

An optical telescope is visual and interesting. A radio telescope is an electronic instrument and you can’t really see a lot of what makes it work. When it’s done all you get is a computer printout.
Comments from an anonymous NSF referee.

Foreword

I know Ken Kellermann, well. We both did our PhDs in radio astronomy in the 1960s, supervised by the famous radio astronomer John Bolton. Ken got his lessons on how to build a telescope and do research when John was building the Owens Valley Observatory at Caltech while I started building the interferometer at Parkes when John and Ken moved from Caltech to Australia. Many years later I spent a challenging but rewarding 7 years working for NRAO as the first director of the newly completed VLA radio telescope in New Mexico. This was sandwiched between my time at Westerbork and the Australia Telescope. To Ellen Bouton, we owe a great debt for the legacy of NRAO’s extensive archives of historical material which underpin the impressively detailed source material used in this book. Sierra Brandt’s background as a historian of twentieth-century science nicely complements the contributions of the other two authors.

While this book is very clearly focused on the development of the US National Radio Astronomy Observatory (NRAO), it touches on many more broader issues, including the birth of a national facility, the open access policy for scientific research, the wider societal implications of searching for extraterrestrial intelligent life, and lessons learned from major construction projects. It is far more than just the history of NRAO. By discussing the development of NRAO in an international context the authors have also written a history of the development of radio astronomy as seen from a US perspective. They start from the well-covered ground when Karl Jansky of the Bell Telephone Laboratory discovered radio emission from the Milky Way in 1933, through the somewhat idiosyncratic but innovative experiments over the next decade by one individual, Grote Reber, to the major technology developments during World War II.

Radio astronomy had started in the USA, but in the immediate postwar period, other countries, notably the UK and Australia, embarked on vigorous programs of exploration of the radio sky, taking advantage of the influx into astronomy of the high caliber scientists and engineers who had developed the radar technology. Quoting the authors: “Early American radio astronomy did not have the same big impact as the programs in the UK and Australia.” This external pressure was a major factor galvanizing the US scientific community into activity. In this time period, the obvious way forward was to build an even bigger dish than the British (250 foot) or the Australian (210 foot) radio telescopes. With the vision of building a very large antenna of perhaps 600 foot diameter this was “big science.”

The establishment of a national radio astronomy facility in the USA is a fascinating story with many obstacles and detractors. The authors provide excellent context for the formation of NRAO by including detailed archival research on the steps that were involved. This is a well-informed and deep analysis of how decisions were being made. The National Science Board had already made a declaration for government support of large-scale basic scientific facilities (i.e., support for big science) and had given the construction of a major radio astronomy facility as an example. This impacted NSF policy and was the beginning of the national facility concept. A concept which was pioneered by the USA and later adopted in many other countries. However, establishing a national facility was not supported by all parties and throughout the book we can read lively accounts of the ongoing debate for and against the “big science” national facility concept instead of smaller groups of young innovative scientists based in the universities. This reached an extreme in the ongoing disagreements and confrontations between Merle Tuve (DTM) and Lloyd Berkner who was the president of AUI, the organization that ran the Brookhaven National Laboratory, a “big science” national facility for particle physics research.

Lloyd Berkner had a huge impact on the development of the National Radio Astronomy Observatory. The authors note that Berkner may not have the name recognition as some of the other American postwar science policy leaders such as Vannevar Bush, Robert Oppenheimer, or I.I. Rabi, but perhaps no one had a broader impact on mid-twentieth-century science policy. They include one extraordinary example: Berkner became the first Chair of the National Academy of Science Space Studies Board and he sent a strongly worded memorandum to NASA Administrator James Webb stating that “Scientific exploration of the Moon and planets should be clearly stated as the ultimate objective of the U.S. space program. ... Scientific exploration of the Moon and planets must at once be developed on the premise that man will be included. Failure to adopt and develop our national program upon this premise will inevitably prevent man’s inclusion, and every effort should be made to establish the feasibility of manned space flight at the earliest opportunity.” Less than 2 months later, in a special address to joint session of Congress, President John F. Kennedy conveyed Berkner’s message stating that “this nation should set as a goal before this decade is out, of landing of a man on the moon and returning him safely to the Earth.”

When David Heeschen became Director of NRAO in late 1962 he presented a clear view of the role of a National Facility. NRAO’s multiple r­esponsibilities included providing equipment and aid for visiting scientists, anticipating the need for future developments in radio astronomy, and playing a leading role in developing new instrumentation. As Director of one of NRAO’s facilities (VLA) in the 1980s, I came to appreciate the value of Heeschen’s vision, and I later implemented similar policies when establishing the CSIRO radio telescopes in Australia as a National Facility.

The book is most appropriately titled Open Skies, a concept which values open access to research facilities as the most effective way to make scientific progress. The NRAO has been the leading advocate for this concept in astronomy and has set the path which has been followed by almost the entire radio astronomy community worldwide. One of the authors, Ken Kellermann, has been a visionary advocate for Open Skies so it is no surprise that it features both in the title and throughout this book.

At the inception of the National Facility concept, Berkner and his deputy Richard Emberson proposed the open access model: “all qualified scientists without regard to institutional affiliation would have access to the facility,” thus “insuring maximum scientific progress.” This was the policy adopted by NRAO and is referred to as “open skies,” following the nomenclature adopted by the international airlines governing reciprocal landing rights. In October 1959, Heeschen famously wrote to the editors of the three main astronomy journals in the USA requesting that they publish the following statement: “The facilities of the Observatory are open to any competent individual with a program in radio astronomy, regardless of institutional affiliation.” NRAO then took this a step further by not requiring previous radio experience and by including international as well as national institutes.

For over 50 years almost all radio observatories in the world have obtained mutual advantage from this policy but, sadly, as discussed in the last chapter, the SKA participating countries are now questioning whether to continue this tradition.

When reading the account of the construction of the first big dish in Chap. 4, I was struck by the various comments about the need to finish construction before the telescope was obsolete. Similar comments had been made during the construction of the Parkes 210 foot telescope, and there seemed to be a feeling that there were only a few projects that the single dish would do well, so after a short burst of activity the big dishes would have no lasting impact. At the time, there seemed to be almost no realization that in reality it was these flexible instruments that would go on to study many of the new unanticipated discoveries.

Many of us in the broader radio astronomy community had heard about the problems encountered in the construction of the NRAO 140 Foot Telescope in the USA and the practical limitations that were imposed by some poor design decisions, such as the use of an equatorial mount rather than an alt-az mount. However, this is the first time we can read a frank and detailed account of how it overran its budget by a factor of 3, was 5 years late on a 2-year construction timescale, and still did not reach the specifications of the larger and cheaper 210 foot Parkes telescope completed in Australia a few years earlier. Bernard Burke described the 140 Foot radio telescope as having “served well, but its equatorial geometry is antique, its structural flexure is dreadful, its surface quality is inferior, its maintenance is expensive and man-power intensive, and its pointing is substandard.” An interesting quote, and measure of the times, was related to the use of computers for coordinate conversion if using an alt-az mount: “... the operation of a precision scientific instrument should not be trusted to a computer.” This is almost identical to the view that Bernard Mills expressed in Australia at that time when he suggested that aperture synthesis would never be practical if it depended on the use of an electronic computer.

But this book goes further; the authors have analyzed, like a scientific research paper, the reasons behind the decisions and the implications of the management structure that had been established. This concludes with an excellent summary of lessons learned; some written by Dave Heeschen, who was the senior member of the NRAO Scientific Staff during most of the 140 foot construction, and others summarized by the authors. Since it is clear that we have still not learned from these mistakes in our subsequent and even current management of big projects, I repeat them here in this Foreword for maximum impact.

In 1992, Dave Heeschen summarized the 140 Foot project as follows:

The 140 Foot is a classic example of how not to design and build a telescope. The design specs were set by a committee of outside consultants who had no responsibility or accountability for the final result, and who gave liberally of poor advice. The 140-foot project leader, a very nice gentleman who was [assistant] to the president of AUI and responsible for the entire feasibility study that led to the establishment of NRAO, uncritically accepted all this advice. The telescope was originally going to have an alt-az mount because the consulting engineers thought that was the most feasible…. But the steering committee membership changed from time to time and finally had on it a prominent and outspoken scientist who insisted the mount should be equatorial…. Then the solar astronomer on the steering committee decided that the telescope should be able to observe the Sun from sunrise to sunset on June 22 each year. The errors made in bidding, contracting, and construction were even worse…. AUI wound up with a fixed price contract, for $4 million, with a company—E W Bliss—that really didn’t want the job, except for one enthusiastic vice [president] who apparently bullied them first into accepting the final contract. He quit shortly afterward and AUI was left with a semi-hostile contractor.

Some important lessons were learned, or should have been learned, from the 140 Foot experience:

1. Beware of the lowest bidder
2. Be sure the contract is clear about who is responsible for what
3. Finish the design before starting construction
4. Establish clear points of contact, authority, and responsibility on both sides
5. Have a firm understanding of when the antennas will be delivered, with penalties for late delivery
6. Do not take committee advice too seriously
7. Have good in-house expertise

In October 1961, Joe Pawsey, from the CSIRO group in Australia, was offered the directorship of NRAO. He visited in March 1962 and started making plans for the future of NRAO, including the use of interferometers to increase angular resolution. Pawsey was diagnosed with a brain tumor in May 1962, returned to Australia, and died in November 1962. Dave Heeschen, from the NRAO staff, had been acting director and became director on October 19, 1962.

The concept of a radio telescope with angular resolution comparable to that obtained in the optical emerged in the early 1960s. While it was clear that a single dish could never achieve this, the radio interferometers certainly could, and this was already being demonstrated in Australia and in the UK. NRAO started down this path in competition with Caltech and its proposed Owens Valley Array based on John Bolton’s highly successful interferometer. In 1970, NRAO finally won this competition (described as the period of the NRAO-­OVRO wars) after they had hired some of the best young radio astronomers from Caltech.

Dave Heeschen certainly learnt from his own list of lessons and under his leadership NRAO brought the VLA project to completion in 1980, on schedule and close to the planned $78M budget appropriation. The VLA exceeded almost all its design specifications and has been by far the most powerful and most successful radio telescope ever built and, arguably, the most successful ground-based astronomical telescope ever built.

“The Bar is Open” was a well-known Heeschen alternative to an after-­dinner talk which is used as the title for a chapter on one of the most productive periods of radio astronomy research at NRAO. When Dave Heeschen retired, he gave a talk: “advice to future directors and managers”:

1. Hire good people, then leave them alone.
2. Do as little managing as possible.
3. Use common sense.
4. Do not take yourself too seriously
5. Have fun

I also recall another item of wise advice I received from Dave as I embarked on my first serious management role as VLA Director: “It’s sometimes more important to make a clear decision than to get the decision right—but do try to get it right more than half the time!”

The chapter on millimeter wavelength (mm) astronomy is not just a summary of NRAO’s involvement in mm astronomy, a field which was opened up and led by the USA, but an overview of all international mm astronomy efforts. The radio astronomy millimeter field developed in a very different way compared to the meter and centimeter wavelength astronomy. In the beginning millimeter wave receivers were bolometers with no spectroscopic capability and with poor sensitivity. As a result, there was a very limited scientific case with few observable sources, so the NRAO 36 foot at Tucson was a high-risk exploratory development. But with the unexpected discoveries of a plethora of spectral lines, millimeter radio astronomy became one of the hottest topics in radio astronomy, leading eventually to the billion-dollar ALMA project.

The book includes a great sequence of stories about building big telescopes for radio astronomy. These are all linked to NRAO, but reach well beyond NRAO as a result of NRAO’s strong influence on developments in radio astronomy throughout the world.

The authors analyze in some detail the actual US funding process for a number of major proposals: 140 foot, VLA, VLBA, GBT, and ALMA. In particular, one author (KIK) was directly involved in the VLBA proposal and associated funding process. These actual situations illustrate the difference between the simplistic notions of proposal, review, and funding decision, with the real-life process. This chapter on the VLBA is not just a part of NRAO history but a great historical overview of all VLBI developments by an expert who lived through this era. VLBI experiments, especially those involving space missions, are among the most complex international projects that ever succeeded, involving different institutes, countries, and science agencies. These firsthand stories provide exceptional examples of successful scientific collaboration. Kellermann recounts his involvement in a VLBI collaboration with Russia in the peak of the Cold War.

The Sugar Grove 600 foot radio telescope, referred to by Harvard radio astronomer Edward Lilley as “a radio telescope fiasco,” is also included. It is a story about a classified defense telescope being built near the Green Bank Observatory that has not been told before.

To maintain its viability through the period of traumatic delays in the construction of the 140 Foot dish, NRAO built a simpler, inexpensive 300 Foot transit antenna. At this time this 300 Foot Radio Telescope was one of the most powerful radio telescopes in the world and became an immediate success. For the first time, NRAO had a world-class instrument that was attractive to both visitors and NRAO staff. The successful completion of the 300 Foot transit radio telescope probably saved Green Bank from a premature closing resulting from the continued debacle with the 140 Foot antenna project. From the start of 300 Foot observations, the observatory operated as the first true visitor facility for radio astronomy.

But the 300 Foot story does not stop there. In 1988, NSF planned that the 27-year-old NRAO 300 Foot transit telescope be closed in order to provide funds for operating other new astronomical facilities. But when the 300 Foot Telescope unexpectedly collapsed in November 1988, it was reported in the media as a national disaster for US astronomy. West Virginia’s Senator Byrd demanded that the telescope be replaced. The NSF had other plans, but Byrd was able to include $75M in the 1989 Emergency Supplemental Appropriations Bill, which funded the world’s largest (100-m) fully steerable dish for the Green Bank Telescope, and its chequered story makes another fascinating chapter.

As we approach the end of this book about the genesis of a national big science facility with all the fascinating stories about the many projects it engendered, we again return to the theme of collaboration at an international level with the construction of ALMA and the US involvement in the beginning of the SKA. The book concludes with discussions of closures and divestments, but this is offset by a vision for the Next Generation VLA (ngVLA) which is the US-proposed incarnation of the originally conceived SKA-high.

After 60+ years of progress we still find many lessons that still have not been learned, but this book may go some way to redressing this with its eloquent discussion of what happened in one field, coauthored by one of the experts who has participated directly in many of these developments.

Preface

On April 27, 1933, at the annual meeting of the US National Committee for the International Union of Radio Science (URSI) in Washington DC, less than 50 years after Heinrich Hertz had demonstrated the propagation and detection of radio waves, Karl Guthe Jansky reported that he had detected radio signals from the center of the Milky Way. Jansky had no background in astronomy and was not searching for extraterrestrial radio signals, but was working for the AT&T Bell Laboratories to locate the source of interference to transatlantic telephone circuits. Only about 30 people were present to hear Jansky’s dramatic announcement, one that would change the course of twentieth-century astronomy and lead to at least eight future Nobel Prizes. Although Jansky’s discovery aroused great public interest, nearly two decades would pass before the American scientific community became sufficiently interested to invest in this emerging new field of astronomy. By that time, scientists trained in wartime radio and radar technology, primarily in Britain and Australia, had made a series of spectacular astronomical discoveries, and the USA was in danger of falling behind in this rapidly growing field, with obvious implications for technology, for military use, and for national prestige.

Prior to Jansky’s discovery, astronomical research was confined to the narrow optical window between 4000 and 7000 Angstroms (400–700 nm), only about a factor of two in wavelength. With the spectacular postwar development in electronic instrumentation and the resulting march toward shorter and shorter wavelengths, radio observations today cover the broad spectrum between less than 1 mm to more than 10 m, a range of about 105 in wavelength. The subsequent rapid growth of space programs extended astronomers access to the entire electromagnetic spectrum from the infrared to the ultraviolet, X-ray, and gamma-ray, all of which are obscured by the earth’s atmosphere. However, radio astronomy was the first outside the traditional optical window and resulted in the discovery of a wide range of previously unrecognized cosmic phenomena and many new previously unrecognized constituents of the universe. These included solar radio bursts, electrical storms on Jupiter, the s­o-­called greenhouse effect on Venus leading to its extraordinarily hot surface temperature, precise tests of general relativity, the rotation of Mercury, the first exoplanets, radio galaxies, quasars, pulsars, cosmic masers, and cosmic evolution. The discovery of the microwave background by Arno Penzias and Bob Wilson in 1965 revolutionized cosmology and, interestingly, was made at the same AT&T Bell Laboratories as the initial discovery by Jansky of cosmic radio emission some three decades earlier.

The early pioneering radio astronomy observations were largely carried out by a single individual or small group who conceived of an experiment, designed and built the equipment, carried out the observations, and analyzed the resulting data. The 1956 establishment in the USA by the National Science Foundation (NSF) of the National Radio Astronomy Observatory (NRAO), operated by Associated Universities, Inc. (AUI), changed the culture and ultimately impacted all astronomy, not just radio astronomy. Before NRAO, US astronomical observatories were primarily privately funded through generous gifts from wealthy individuals like Charles Yerkes, James Lick, Percival Lowell, Andrew Carnegie, and John D. Rockefeller, and the philanthropic foundations which they established. The European-based observatories were often state supported, but they, like their private American counterparts, were used nearly exclusively by their own staff members.

Following the lead of the physicists who had created the Brookhaven National Laboratory (BNL), the NRAO was established to provide scientific instruments that were too costly for individual universities to build and operate. Although originally intended to provide opportunities for American radio astronomers to compete in the rapidly developing new field, with the availability of its first instrument, the 85 Foot Howard E. Tatel Telescope, NRAO developed a more broadly welcoming policy and announced its visiting scientist program on page 1179 of the October 30, 1959, issue of Science:

The National Radio Astronomy Observatory was established by the National Science Foundation to make available to scientists from any institution facilities for research in radio astronomy…. The facilities of the observatory are open to any competent scientist with a program of work in radio astronomy, regardless of institutional affiliation.

Under the wise leadership of its young Director, Dave Heeschen, as additional telescopes were completed—the 300 Foot, the 140 Foot, the Green Bank Interferometer, the 36 Foot millimeter telescope, and eventually the Very Large Array (VLA)—NRAO facilities continued to be available to any scientists with a good program, independent of their institutional or national affiliation. This concept, which has become known as “Open Skies,” after the Open Sky agreements which regulate international airline traffic, ultimately was adopted by nearly all major ground- and space-based American as well as international astronomical facilities. When two of us (Kellermann and Bouton) interviewed Dave Heeschen on July 13, 2011 (see https://science.nrao.edu/about/publications/open-skies), we asked, “What was the best thing you did during your years as Director, the thing that had the biggest impact?” Heeschen responded, “I think it’s the establishment of the concept of the national observatory and the free use of the telescopes by people … [T]hat I think was a really good thing that came out of it, and it’s something which is persisting, you know, till this day. Everybody uses everybody else’s telescopes in one way or another.”

In his definitive book, Cosmic Noise (Cambridge: Cambridge University Press, 2009), Woodruff T. Sullivan III documented the explosive growth of radio astronomy from Jansky’s unexpected discovery to the exciting postwar programs in Australia, in the UK, and, to a lesser extent, in the USA. Sullivan’s book ends in 1953, 20 years after Jansky’s discovery. The first discussions leading to the establishment of a national radio astronomy facility started in the early 1950s, and began the evolution of astronomy to a user-based, hands-off, big-science culture. In Open Skies, we have tried to pick up where Sullivan left off, describing the tumultuous circumstances leading to the creation of the NRAO, the difficult years which almost led to the closing of the observatory before it really got started, the later construction of the VLA, the Very Long Baseline Array (VLBA), and the Green Bank Telescope (GBT), along with the pioneering explorations into millimeter wavelength astronomy. It was a period which saw an unprecedented series of astronomical discoveries, mostly made possible by the explosive growth in radio astronomy techniques during the latter half of the twentieth century.

In planning the organization of Open Skies, we opted against a strictly chronological story, but instead deal with each major area of NRAO’s contributions, arranged in separate chapters in approximate time sequence with each chapter organized in roughly—but not completely—chronological order. As background for those readers not familiar with the extensive literature on the early development of radio astronomy, we have included two introductory chapters about events which led to the start of discussions about establishing a national radio astronomy facility. A more detailed account of the people and activities during the early years in Green Bank is given in But It Was Fun, ed. J. Lockman et al. (Green Bank: NRAO). We have included a listing of Abbreviations and Acronyms, which includes abbreviations used in the text and in endnote citations (Appendix A) as well as a Timeline (Appendix B) at the end of the book.

Two of the authors of Open Skies, Ellen Bouton and Ken Kellermann, have had a long association with NRAO. Bouton began work in the NRAO library in 1975; in 1983, she became the NRAO Librarian and since 2003 has been the NRAO Archivist. Kellermann joined the NRAO scientific staff in 1965. He was involved in most of the activities described in Open Skies since that time, especially the development of VLBI and planning for the VLBA, and from 1995 to 2003 was the NRAO Chief Scientist. Sierra Brandt brought her background in the history of astronomy to the NRAO/AUI Archives between 2011 and 2013 and has been a consultant since.

In researching the growth of NRAO and American radio astronomy, we have been aided by the collections in the NRAO/AUI Archives. Holdings include the formal records of NRAO, papers of many early NRAO staff members, as well as the personal papers of some of the pioneers of US radio astronomy, especially Grote Reber, as well as Ronald Bracewell, Bernard Burke, Marshall Cohen, John Kraus, and Gart Westerhout.

We are grateful to the AUI Board, and especially Patrick Donahoe and Robert Hughes, for making the records of AUI Board meetings available. We must also acknowledge the resources of many other institutional archives and of the Library of Congress. Shelly Erwin and Loma Karklins gave their generous help and support during many visits to the Caltech Archives to examine the papers of Jesse Greenstein, Lee DuBridge, Alan Moffet, and Gordon Stanley. Gordon’s children, Teressa and Luise, kindly made available some of their father’s personal papers. Janice Goldblum at the National Academy of Sciences Archives provided us with access to the records of the 1964 Whitford and the 1972 and 1973 Greenstein reviews of astronomy and astrophysics, as well as records of the early meetings of the USNC-URSI commission on radio astronomy. Elise Lipkowitz facilitated access to the records of the NSF’s National Science Board (NSB) during the critical period surrounding the establishment and early years of NRAO. Shaun Hardy helped us research the papers of Merle Tuve at the Carnegie Institution Department of Terrestrial Magnetism. Robin McElheny at the Harvard University Archives facilitated our access to the papers of Harvey Brooks, Ed Purcell, Bart Bok, Donald Menzel, and Leo Goldberg. Brian Andreen at the Research Corporation kindly gave us access to their files related to their long-term support of Grote Reber. Bernard Schermetzler at the University of Wisconsin Archives made available Karl Jansky’s letters written to his father in 1932 and 1933, which contain regular reports on the work leading to his remarkable discovery, along with snippets of life during those difficult depression years.

Tony Tyson and Bob Wilson provided much valuable information on Karl Jansky from the Bell Laboratories Archives. Karl Jansky’s widow, Alice, and their children, Ann Moreau and David, shared with us memories of Karl Jansky and the environment at Bell Labs during the 1930s. Miller Goss kindly made available his extensive research on Joe Pawsey, including privately held Pawsey family papers provided by Joe Pawsey’s son, Hastings Pawsey. Nora Murphy, MIT Archivist for Reference, Outreach, and Instruction, and Bonny Kellermann helped provide the recording of Otto Struve’s 1959 Karl Taylor Compton Lecture. Steven Dick kindly gave us copies of Frank Drake’s 1961 presentation at the Washington Philosophical Society, which led to the first conference on the search for extraterrestrial intelligence. We are also indebted to Richard Wielebinski for sharing with us his inside view of the activities leading to the construction of the German 100 m radio telescope.

Many of our colleagues read early versions of chapters, provided additional information, and made valuable suggestions for improvement. We thank Jaap Baars, Barry Clark, Marshall Cohen, Steven Dick, Bob Dickman, Pat Donahoe, Phil Edwards, Miller Goss, Dave Hogg, Tony Kerr, Jay Lockman, Jeff Mangum, Jim Moran, Vern Pankonin, Marian Pospieszalski, Jon Romney, George Seielstad, Richard Schilizzi, Jill Tarter, Paul Vanden Bout, Cam Wade, Craig Walker, and Sandy Weinreb, each of whom reviewed one or more chapters. We are especially grateful to Tony Beasley, Ron Ekers, and Peter Robertson, who reviewed the entire manuscript and made many helpful suggestions, and whose careful eyes caught numerous errors others had missed. Rebecca Charbonneau, Heather Cole, Michele Kellermann, Sheila Marks, and Nicole Thisdell gave us valuable editorial help and advice, and Jeff Hellerman helped prepare images for both content and cover. Ramon Khanna, our Springer editor, provided valuable advice and ­support throughout our project. Of course, any remaining errors are the responsibility of the authors.

We are especially grateful to Woody Sullivan, who generously donated to the NRAO/AUI Archives the audio recordings and available written transcripts of the interviews he conducted between 1971 and 1988 with 225 different radio astronomers, as well as the working papers he compiled on the interviewees and on other scientists. Author interviews of Mike Balister, Bernie Burke, Fred Crews, Frank Drake, Cyril Hazard, Dave Heeschen, Dave Hogg, Bill Howard, Harvey Liszt, Tom Matthews, Kochu Menon, Mark Price, Grote Reber, Ted Riffe, and Cam Wade gave us additional valuable insights which were important in writing Open Skies.

We wish to thank Tony Beasley and AUI for their long support of the NRAO/AUI Archives and, in particular, for funding to make this work available as an open access publication. And finally, but certainly not least, we also want to thank Michele, Ron, and Dana for their long-suffering tolerance and support of this project.

Charlottesville, VA, USA	Kenneth I. Kellermann
Charlottesville, VA, USA	Ellen N. Bouton
Providence, RI, USA	Sierra S. Brandt

Contents