TECH, aoaot Mii22 PB 151387 ^0.28 ^5oulder laboratories A HISTORY OF VERTICAL - INCIDENCE IONOSPHERE SOUNDING AT THE NATIONAL BUREAU OF STANDARDS BY SANFORD C. GLADDEN U. S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS IE NATIONAL BUREAU OF STANDARDS Functions and Activities The Functions of the National Bureau of Standards are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent with these standards: the determination of physical constants and properties of materials: the development of methods and instruments for testing materials, devices, and structures; advisory services to government agencies on scientific and technical problems; in- vention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes basic and applied research, development, engineering, instrumentation, testing, evaluation, calibration services, and various consultation and information services. Research projects are also performed for other government agencies when the work relates to and supplements the basic program of the Bureau or when the Bureau's unique competence is required. The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover. Publications The results of the Bureau's work take the form of either actual equipment and devices or pub- lished papers. These papers appear either in the Bureau's own series of publications or in the journals of professional and scientific societies. The Bureau itself publishes three periodicals available from the Government Printing Office: The Journal of Research, published in four separate sections, presents complete scientific and technical papers; the Technical News Bulletin presents summarv and preliminary reports on work in progress; and Basic Radio Propagation Predictions provides data for determining the best frequencies to use for radio communications throughout the world. There are also five series of nonperiodical publications: Monographs, Applied Mathematics Series, Handbooks, Miscellaneous Publications, and Technical Notes. Information on the Bureau's publications can be found in NBS Circular 460, Publications of the National Bureau of Standards (SI. 25) and its Supplement ($1.50), available from the Superintendent of Documents, Government Printing Office, Washington 25, D.C. NATIONAL BUREAU OF STANDARDS technical ^iote No. 28 A HISTORY OF VERTICAL- INCIDENCE IONOSPHERE SOUNDING AT THE NATIONAL BUREAU OF STANDARDS by Sanford C. Gladden Central Radio Propagation Laboratory September 1959 NBS Technical Notes are designed to supplement the Bu- reau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be listed or referred to in the open literature. They are for sale by the Office of Technical Services, U. S. Depart- ment of Commerce, Washington 25, D. C. DISTRIBUTED BY UNITED STATES DEPARTMENT OF COMMERCE OFFICE OF TECHNICAL SERVICES WASHINGTON 25, D. C. Price $2,00 National Bureau of Standards OCT 3 1960 103,555 QC \0D M51S3 Copy £ . Preface This is an attempt to treat in chronological order the devel- opment of vertical incidence ionosphere sounding at the National Bureau of Standards through 1957- Of necessity many phases of the radio work of the Bureau have been omitted or treated lightly as not being germane to the principal purpose of this history. With the exception of early workers in the field, names of individuals are to be found only in the references Source material includes the monthly, quarterly, and annual reports of Section 6, Division 1 (the old Radio Section), and of the Central Radio Propagation Laboratory; reports of the Interservice Radio Propagation Laboratory; the declassified reports of the International Radio Propagation Conference; the Bureau of Standards Journal of Research; the NBS Technical News Bulletin; published and unpublished reports of NBS; periodical literature, such as the Proceedings of the Institute of Radio Engineers, the Physical Review, Nature, Journal of Geophysical Research (formerly Terrestrial Magnetism and Atmospheric Electricity), and Science. Times of service of NBS personnel in charge of field stations have been verified through station correspondence as well as in many instances by personal contact with the individuals concerned. CQ U CO & CO -P CQ Ch O P« 03 CD pq H CO o •H -P CO OJ -p O CQ •H OSh +3 CO u o § 1-3 £h dcu H oPi pq ii ACKNOWLEDGMENTS Department of Terrestrial Magnetism, Carnegie Institution of Washington, for the photographs of the equipment used by Breit and Tuve, photographs of the records obtained with this equipment, and details of operation of the manual and automatic sounding equipment developed by the organization. U. S. Army Signal Radio Propagation Agency, for the photographs of its field stations and details of their early operation. Geophysical Institute of the University of Alaska, for photographs of its field station and the DTM automatic ionosonde. The Department of Terrestrial Magnetism also furnished a photograph of the same ionosonde. Father J. J. Hennessey, S. J., of the Manila Observatory, for the photo- graph of the Baguio field station. A. A. Giesecke, of the Geophysical Institute of Huancayo, for photo- graphs of the Huancayo and Talara field stations. Dr. Jorgen Rybner, of the Danish URSI Committee, for the photograph of the Godhavn field station. S. Thorkelsson, of the Icelandic Post and Telegraph Administration, for the photograph of the Reykjavik field station. T. R. Gilliland, present field station engineer for NBS, for the photo- graphs of the first two ionograms made with the initial auto- matic multifrequency ionosonde of NBS, as well as much infor- mation concerning the early work at NBS. Dr. R. A. Helliwell, of the Radio Propagation Laboratory, Stanford University, for the photograph of the Stanford field station. At the Boulder Laboratories, NBS H. G. Sellery, in charge of the Field Operations Group, for making the station correspondence available for study. E. L. Kilpatrick, for the photographs of the ionograms made with the low- frequency ionosonde. A. H. Shapley, Chief, Sun-Earth Relationships Section, R. W. Knecht, and T. E. Van Zandt for critical evaluation of the text material. W. B. Chadwick and S. M. Ostrow, Regular Propagation Services Section, for reading the rough draft of the text. 111 —- INDEX Page I. Historical summary to 1927 1 II. Early work at the National Bureau of Standards (I929- 1946) 1. Measurements of virtual height at fixed frequencies 4 2. Early NBS ionosondes 12 III. The Interservice Radio Propagation Laboratory (1942-1946) 1. Organization and functions 12 2. The International Radio Propagation Conference (1944) — 18 3. Types of ionosondes used by stations affiliated with IRPL - 18 IV. Development of practical applications. 1. Determination of maximum usable frequencies 20 2. Sudden ionosphere disturbances 22 3- Predictions of ionospheric phenomena------ — ---------- 22 a. Prediction of critical frequencies 22 b. The longitude effect 24 c. Forecasting of ionospheric storms------------------- 24 d. MUF over long paths — 25 V. The Central Radio Propagation Laboratory (since 1946) 1. Organization and functions 25 2. Development of the CRPL Model C ionosondes 28 3. Antenna testing and design -_______- --____-__—-__ 29 4. Ionospheric field stations operated by or associated with NBS 31 5. Reduction of ionospheric data 32 6. Data inspection — 43 7- Improvement and extension of prediction methods — 44 8. Radio warning services — 45 9- Vertical sounding at low frequencies 46 10. Ionospheric research — -_ — __-_-_--____-_ 47 VI. International programs of ionospheric research 1. The Second International Polar Year-- 48 2. CRPL and the International Geophysical Year 49 a. The general program 49 b. World Warning Agency- — _ --_ 50 c. World Data Centers —— 51 d. Data processing 52 IV - APPENDICES I. Early NBS lonosondes Page 1. First NBS automatic mu It i frequency ionosonde 53 2. Model A ionosonde 55 3- Model B ionosonde — - 58 II. Type of ionosondes used by stations affiliated with IRPL a. Types developed by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington --- — 59 1. Automatic multi frequency equipment----- 59 2. Manual ionosphere recorder Model 1 59 3- Manual ionosphere recorder, modified Model 1 ------- 6l k* Manual ionosphere recorder Model 3 --— — 6l b. British frequency modulation Type 2^9 Sk c. Australian automatic multifrequency ionosonde (Model Mark V) 66 d. Ionosondes developed by various laboratories associated with NBS 68 1. Harvard University —— - — --------— 68 2. Leland Stanford University 68 3. Louisiana State University 73 k. Signal Corps Type AN/CPQ-T (XE-l) 73 III. Development of the CRPL Model C ionosondes 1. Model C-l - 76 2. Model C-2 76 3. Model C-3 -- 81 k. Model C-k - 83 IV. Details of operation of field stations ---------— - — —-— 85 V. Summary of information regarding stations established before 1957 - HI VI. Summary of information regarding stations established in 1957 and I958 - 116 VII. References Page 1. Section I --- - 118 2. Section II - — 119 3. Section III - 121 k. Section IV 123 5. Section V 125 6. Section VI 133 vi A HISTORY OF VERTICAL- INCIDENCE IONOSPHERE SOUNDING