For the early history of radar astronomy, a number of archival sources were consulted. The Historical Archives, U.S. Army Communications-Electronics Command, Ft. Monmouth, NJ, have several boxes of material on the pioneering lunar radar work of John DeWitt, but no such archival material was found on the radar work of Zoltan Bay, with the exception of the documents in the possession of his widow. The Naval Research Laboratory Historical Reference Collection, Office of the Historian, was not a ready source of information on the lunar radar work carried out there; much of the Laboratory's records remain classified. In contrast, the archives of Jodrell Bank, housed at the University of Manchester, contain a wealth of open information on radar astronomy, and a computerized index is available.
Radar research on meteors began at Stanford University as early as the 1950s. The university archives, however, hold no records relevant to either the early or later work done there. The only records available are those of the Stanford Center for Radar Astronomy, which for the most part consist of a large collection of offprints that document the Center's research results. Von Eshleman, the Center's director, was a far more important source of documentation.
Records relating to radar astronomy at the Arecibo Observatory are located for the most part in filing cabinets at the National Astronomy and Ionosphere Center (NAIC) offices on the Cornell University campus and are not normally open to researchers. Among the most useful of those records are the quarterly reports to the NSF and copies of Center for Radiophysics and Space Research (CRSR) research publications. The NAIC library retains copies of dissertations completed at the Arecibo Observatory. The CRSR, located in the same building, has the earlier ARPA reports. The library of the Arecibo Observatory contains additional reports, program plans, dissertations, and other materials. The minutes of the open sessions of the National Science Board were helpful, as were the archives of the AFCRL at Phillips Laboratory, Hanscom AFB, although the amount of documentation at each place was lean.
In contrast, an overwhelming abundance of documents relating to the history of radar astronomy were found at MIT and Lincoln Laboratory. The Lincoln Laboratory Library Archives contain both documents and photographs, while the MIT Institute Archives and Special Collections is a treasure trove of documentation, including NEROC materials. The Pusey Archives, Harvard University, hold additional NEROC documents. In general, the MIT, Lincoln Laboratory, and Harvard materials are available to researchers; examination of the Pusey papers requires written permission from the director of the Harvard College Observatory, though. A small building near the Haystack Observatory named for its first director, Paul Sebring, holds logbooks and other records relating to the Millstone and Haystack facilities, but those records normally are closed to researchers.
Documents relating to radar astronomy at Goldstone can be found in the Jet Propulsion Laboratory archives. Magellan materials, although somewhat organized, have not been fully integrated into that portion of the archives open to researchers. Also, a smaller batch of materials, initially removed from document storage for a history of the Deep Space Network and slated for integration into the JPL archives as the Peter Lyman Collection, was especially useful.
 For further documentation of the NEROC saga, see the Archives of the Smithsonian Institution, in particular, the Office of the Secretary and the Under Secretary collections. The papers of William Brunk, at the NASA History Office, and the Historian's File, at the National Science Foundation, held valuable materials on the first upgrading of the Arecibo facility. The library of the National Science Foundation and the archives of the National Academy of Sciences also held useful secondary sources.
A significant number of documents relating to radar astronomy are in the possession of individuals who made the materials available exclusively for the writing of this history. Until the day arrives when (and if) those documents are entrusted to an archive, the above noted depositories will be the chief source of documentation for the history of radar astronomy. In addition, materials gathered or created in the process of writing this history, including photocopied documents, notes, and oral history transcripts, have been deposited with the NASA History Office for consultation by researchers.
Because planetary radar astronomy is a relatively new field, virtually all of the founders, even those active during the 1940s, and practitioners are still with us. This project has been fortunate, too, in that with only one exception everyone approached agreed to be interviewed. Two-thirds of the interviews were taped and transcribed. The author alone conducted all interviews with the exceptions of Schaber, Soderblum, and Shoemaker, which were carried out jointly with Joseph Tatarewicz, as noted below. Copies of all transcripts are held by the NASA History Office and the JPL Archives; interviews of individuals formerly with MIT Lincoln Laboratory are also maintained at their archives.
Those interviews not transcribed, as well as the telephone interviews, consist of either notes or tapes on file at the NASA History Office and the JPL Archives. Additional interviews, carried out by dose Alonzo and housed at the JPL Archives, were consulted; they are listed below, too.