IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. COM-22, NO. 4, APRIL 1974 359

INTERFERENCE AND ENVIRONMENTAL IMPACT

Valentino and his colleagues recognize the Navy’s proposed ELF communications system that uses an earth- return circuit to excite the earth-ionosphere cavity repre- sents a potential electrical interference problem. As they point out, the electromagnetic fields produced by Sanguine could influence other systems such as power distribution lines and telephone circuits, and other very long electrical conductors. They describe this interference potential and the techniques useful in mitigating it.

Benedick and Greenberg provide an overview of their laboratory and field studies, completed and in progress, designed to disclose possible effects on organisms of a Sanguine system. They indicate that the ELF electric and magnetic field levels associated with a Sanguine system are about 0.07 V/m and 0.2 gauss, respectively, a t the surface of the earth directly above a buried Sanguine antenna. They have attempted to determine whether adverse biological or ecological effects could be expected from exposure to these low levels. Research results to date show no indication that exposure to ELF field levels associated with a Sanguine system would have any e$ect on biological or ecological systems.

AN ALTERNATIVE TO PROJECT SANGUINE

Davis and Willis propose an alternative low-data-rate system that could operate a t an even lower frequency. For example, at about 0.5 Hz, attenuation in seawater to a depth of 100 m would be only 2.5 dB.compared with 25 dB for 50 Hz. A communications system operating a t this ultralow frequency thus would enjoy an advantage of more than 20 dB over even a Sanguine system in the criterion of loss in seawater. For receivers a t 300 m depth, which may well be reasonable for foreseeable submarine technology, this advantage’would be nearly 70 dB and could outweigh any advantage in information bandwidth possessed by the ELF system. The authors describe how the generation of waves in this band might be possible. Methods involve the modulation of ionospheric conduc- tivity from the injection of plasma clouds into the iono- spher and heating of the lower E region with powerful radio transmitters. They also consider nonlinear processes in the magnetosphere resulting from cold plasma injection and VLF/ULF three-wave interactions. Rather than travelling in the earth-ionosphere waveguide, most of the energy in the generated ULF signal would be ducted more or less along the geomagnetic field lines in the magnetosphere.

Some Early Historical Aspects of Project Sanguine

JOHN MERRILL

Abstract-Early extremely low-frequency (ELF) research and the implementation of Project Sanguine to meet the Navy’s need for secure transmission to submerged fleet ballistic missile (FBM) submarines are outlined. The 1963 “Intensive Test,” which proved the feasibility of ELF reception by a submarine at operational depths, is highlighted.

I INTRODUCTION

N April 1963, the Navy conducted a communication demonstration between a shore-based extremely low-

frequency (ELF) (30-300 Hz) radio transmitter located in North Carolina and a nuclear submarine operating, a t a range of 3200 km, with its receiving antenna near keel depth. Termed the ‘Tntensive Test,” this event estab- lished the fact that a deployed submarine could receive messages from the continental United States (CONUS)

Manuscript received December 6, 1973. The author is with the Naval Underwater Systems Center, New

London Laboratory, New London, Conn. 06320.

without severe reductions in the submarine’s operational capability during reception. This was a most important “first” in the history of subma.rine communications, and this paper describes some of the technical and organiza- tional developments that made the 1963 communication demonstration possible.

HISTORICAL ORIGINS OF ELF (TO 1958)

This section, taken directly from a paper [l] by Wait of the University of Colorado, briefly summarizes the development of the ELF concept prior to the Navy’s interest in ELF transmission as a submarine communica- tions technique.

“The current Sanguine transmitting antenna is to be powered by a series of generators located along a parallel array of insulated cables buried a t depths of the order of 6 ft. These cables are to be up to 160 mi in length, and (‘grounded’’ a t their endpoints. In order to achieve omnidirect,ionality, a second array is envisaged that

360 IEEE TRANSACTIONS ON COMMUNICATIONS, APRIL 1974

is located a t right angles to the first. The principle of operation of such groundtype antennas has been known for a long time. The basic theory goes back to Sommer- feld [a], who in 1.909 and 1926 published a pair of remarkable papers on the exact integral solutions for the fields of dipoles. Of course, the Sanguine antenna is not a Hertzian dipole, but it can be conceived of as a superposition of such dipoles laid end-to-end. In fact, the radiation from such a structure was demonstrated by Beverage and his colleagues in the early twenties, and their results were published in an important but often overlooked paper [SI. Contrary to simple in- tuition, such a grounded dipole radiates predominantly vertically polarized groundwaves. In the ‘LBeverage wave antenna,” the excitation is of a traveling-wave nature, so the pattern is directional. For a center-fed structure, the familiar figure-of-eight pattern results. The horizontally polarized radiation, while always pres- ent, is orders of magnitude smaller than the verticaly- polarized radiation-at least, this is the case for VLF and ELF. An interesting feature of these grounded antennas is that they radiate best over poorly conduct- ing ground. (‘NOW in the Sanguine system, the ionosphere plays a dominating role. Thus, the vertically polarized radiation from the grounded antenna structure couples into the terrestrial waveguide formed by the earth’s surface and the lower portions of the ionized layers in the upper atmosphere. As envisaged by Schumann [4], the whole air-earth-ionosphere space acts as a resonant cavity. The fundamental frequency is approximately 8 Hz when account is ,t.aken of all the complicating influences. “The remarkable propagation characteristics of ELF waves were exhibited in a very significant study by Chapman and, Rtacario [SI. They used the audio- frequency electromagnetic signals from lightning as their source. Such signals, when received a t a distance, are known as atmospherics, or just simply “sferics.” The manner in which the frequency spectra change with distance can be used to ascertain attenuation rates. Chapman and Macario found, for example, that , at 100 Hz, the attenuation rate was only of the order of of 1 dB per 1000 km of path length. No wonder such signals will envelope the globe and lead to cavitylike resonances! Using more refined techniques employing multistation observations, Jean et al. [6] confirmed these results. Only simple waveguide theory was used to in- terpret these early data. But even then, it was recog- nized that a homogeneous and sharply bounded isotropic ionosphere model was not adequate. Thus, Wait [7] in- troduced exponential models for the electron density and considered the influence of the earth’s magnetic field and antipodal focusing effects. A more refined exponential model was then considered by Galejs [SI. Many related investigations were reported in the literature for the next ten years. The reader is referred to two textbooks [9], [lo] that include summaries and bibliographies for the propagation theories.”

NAVY RESPONGE TO POLARIS COMMUNICATION NEEDS

From 1958 to 1962, a wide spectrum of technical efforts were sponsored by the Na+y to improve submarine com- munications for the then forthcoming fleet ballistic missile (FBM) submarines’. Since these submarines were to be deployed a t great distances from the United States, they required reliable transmission of strategic orders in order to ensure their survivability as a deterrent force. Some of the objectives of the new communications needs in- cluded the following.

1) Error-free one-way communication from the Na- tional Command Authority to submerged submarines in their operating areas.

2) Hard copy in the submarines within a fixed period of time.

3) Facilities located within CONUS. 4) No disclosure of the locations of the submarines or

exposure to detection. 5) A system meeting a specified submarine speed

and depth. 6) No severe reduction in the speed or maneuverability

of the submarines. The exploratory development work was supported by

the Bureau of Ships, the Polaris Special Projects Office,’ and the Office of Naval Research (ONR). The scope of the contracted work included analysis, laboratory, and field work for a diverse variety of potential communication techniques.

The Polaris Command Communications Committee (PCCC) was established as a reviewing, evaluating, and recommending authority for the Navy-sponsored in- dustrial effort. The PCCC was part of the Polaris Steering Task Group and, from 1962 to 1964, was under the spon- sorship of the Polaris Communications Office (SP204 of the,,Polaris Special Projects Office). The committee was chaired by a Navy officer and included a broad representa- tion from Government, industrial; and educational activi- ties. The PCCC met at two-month intervals, with more frequent meetings by the various panels and working groups as required.

In the summer of 1958, N. Christofilos of the University of California, Livermore, Calif., during a briefing by the Polaris Special Projects Office, became aware of the Navy’s requirement to communicate from CONUS to a deeply submerged submarine. In August 1958, he pro- posed the use of an ELF electromagnetic wave in the range 10-100 Hz. In this first approach, the idea was to resonate the earth-ionosphere cavity at its natural modes. At that time, information on the Q of the cavity and data on the atmospheric noise level at the frequencies of in- terest were scarce.

The Navy immediately took an intense interest in ELF

Navy Department in 1955 to manage the development of a sea- 1 The Polaris Special Projects Office was established within the

based ballistic missile weapon system.

MERRILL: HISTORICAL ASPECTS OF PROJECT SANGUINE 361

transmission because of the following characteristics of such a system.

I ) Low attenuation in sea water. 2) Low propagation attenuation. 3) Comparatively low sensitivity to atmospheric dis-

turbances caused by nuclear blasts. 4) Better survivability against nuclear attack (ELF

transmitters and antenna arrays lend themselves to dis- persion and hardening). The impact of Christofilos' early concept had several results.

1) ONR supported some immediate investigations of various parameters of the Christofilos concept.

2) The Institute of Defense Analysis called a con- ference in June 1959 to discuss the credibility and feasi- bility of the hypothesis. The central idea of the Christofilos concept passed the scrutiny of those present.

3) The Bureau of Ships, in its negotiation of the PANGLOSS2 contract with RCA Laboratories, in- corporated work aimed a t exploring the potentialities of ELF transmission. The work included atmospheric and submarine noise measurements and an intermediate-scale experiment.

Under the PANGLOSS contract, RCA was to provide technical and administrative services and prototype equip- ment in support of the examination of current and future communications systems for the rapidly evolving Polaris program. The program at RCA involved the full-time assignment, on a task force basis, of up to 100 senior RCA scientists and engineers. The primary forces leading to the 1963 Intensive Test were this ELF work conducted under the PANGLOSS contract and various system con- cept refinements introduced by Christofilos, whose efforts continued to stimulate the submarine communications community until his untimely death in September 1972. The Navy Underwater Sound Laboratory, New London,

Conn., by direction of the Bureau of Ships, was designated Lead Laboratory for PANGLOSS and participated closely with RCA during the life of the contract. The PANGLOSS effort was well documented and was disseminated broadly within the Government and private industry. There were frequent reviews and presentations to the many activities involved in the Polaris effort, with the .PCCC the chief forum of technical exchange, debate, and clarification.

NAVY-SPONSORED ELF RESEARCH

At the beginning of 1959, when the PANGLOSS con- tract started, although there was awareness of the ad- vantages and possible feasibility of the use of ELF for. Navy communications, much data were needed to support the concept:

1 ) Data regarding ELF signal propagation losses; 2) Data regarding the Q of the earth-ionosphere cavity

3) Estimates of the atmospheric noise at ELF. resonances; and

2 PANGLOSS is an arbitrary designation without intrinsic meaning.

To evaluate the signal propagation characteristics of ELF, propagation measurcrnents were made to obtain estimates of the attenuation as a function of frequency. From March to June 1960, the Navy VLF transmitting antenna at Oso, Washington (,Jim Creek), was excited in the frequency range 600-4000 Hz with a 120-kW trans- mitter (radiating 1-100 W). The Jim Creek antenna is a catenary suspended over a valley. The signal measure- ments verified the zero-order-mode propagation model and provided a signal attenuation estimate.

The Jim Creek antenna presented a capacitive load to the experimental transmitter, and the upper value of operating current was limited by corona considerations. From this and other considerations, i t was concluded that looptype transmitting ELF antennas would be su- perior to either short vertical or capacitive impedance types. One lo'optype could be a horizontal wire grounded at the ends and center fed. For this configuration, the radiated field would be determined by the length of the horizontal wire, the current through it, and the conduc- tivity of the earth beneath it.

During June 1960, at an MIT Lincoln Laboratory field site in Ipswich, Mass., radio noise was measured in the frequency band 5-45 Hz. The Q of the earth-ionosphere cavity obtained from these measurements indicated a value of the order of 4 at the fundamental mode [ll].

In August 1960, based on the results of the Jim Creek experiment and the MIT-LL findings, the Navy ELF community rejected the concept of using the earth- ionosphere cavity resonance since the Q from both field measurements was too low (4-5) to provide communica- tion by exciting cavity modes. The Navy now visualized a traveling-wave mode excitation and the use of a more efficient transmitting antenna, i.e., a. horizontal wire grounded at the ends over a poorly conducting ground. Christofilos agreed with these changes, but perhaps more importantly, he examined ELF from the standpoint of a complete system. His investigations established that, at a comparable cost, an ELF system consisting of a series of wires erected over poorly conducting earth can achieve a performance substantially greater than VLF (-15-25 kHz) normalized to ELF data rates.

In October 1960, the concept of an ELF communication signal source using a grid of horizontal center-driven end- grounded transmitting antennas was unanimously recog- nized as an avenue for further investigation. This con- clusion was reached after experimental and theoretical investigations performed primarily by the RCA David Sarnoff Research Center a t Princeton, N. J., and work done by Christofilos at the University of California.

At the request of the PCCC, an ELF committee was formed in January 1961 to assess the research and de- velopment plans for ELF. This ad hoc committee included members from the Stanford Research Institute, the Navy Underwater Sound Laboratory, the Development En- gineering Corporation (DECO) , the Naval Research Laboratory, and the Bureau of Ships.

In May 1961, the ELF committee recommended a

362 IEEE TRANSACTIONS ON COMMUNICATIONS, APRIL 1974

“decisive experiment” that would provide the most realistic technical and economic approach for an opera- tional systcm. The experiment specified the implementa- tion of a complete ELF radio system consisting of a transmitter located in a region of low earth conductivity (2.5 X O/m), a 100-mi (161-km) antenna, and sufficient input power to provide an electric field of 58 pV/m a t a distance of 1000 km. The PANGLOSS ,contract was extended to include a system study for the radiation and reception of ELF signals and a site survey for an experimental transmitting ant]enna. In support of the experiment, ONR sponsored studies of atmospheric noise and earth conductivities to determine the characteristics of these phenomena, develop instrument criteria, and set standards for measurement methods. The decisive experi- ment was scheduled to be completed by March 1964.

Concurrent with the ELF transmitting facility built and tested under Project Sang~ ine ,~ ONR sponsored the lease of a 60-Hz high-voltage transmission line as a signal source for a propagation experiment. The power line ex- tended from Cheyenne to Laramie, Wyo., a distance of about 70 km. At night, the line was disconnected from its normal loads, suitably grounded, and driven a t 60 Hz. A farfield receiving site was located in the Los Padres National Forest, Calif., about 1500 km from the power line in Wyo. Nearfield measurements and correlat.ion of radiation with earth conductivity measurements at the transmitting antenna were also part of this investigation. This work was performed by DECO of Boulder, Colo.

THE INTENSIVE TEST The Intensive Test was that portion of the ELF decisive

experiment in which a concerted effort was made by numerous activities to obtain the data necessary to verify theoretical predictions and provide increased confidence in specifying design parameters.

A site c0nductivit.y survey made for the test in western Virginia and western North Carolina resulted in a 176-km antenna design. The south ground of the transmitting antenna was located in a lake at Lookout Shoals, N. C., and the northern ground was located in a large tobacco field a t Algoma, Va. This antenna was actually in use periodically from 1963 until 1970 and was referred to as Site Alpha (Fig. 1). The antenna was center fed by a transmitt.er consisting of a 120-kW shaker-table amplifier driven by a special keyer-modulator unit. The antenna and transmitter were completed in December 1962, and during the following weeks, various local compatibility problems were resolved. The transmission frequencies used were primarily between 4 and 500 Hz; above 1.50 Hz, power was drastically reduced to minimize interference with local telcphone service. The antenna current for most operations a t or below 1.50 Hz was a nominal 60 A.

Sanguine or Project Sanguine is an arbitrary designation first applied to ongoing ELF research by the Bureau of Ships, Com- munications Systems Branch, in 1962. The term continues to designate work directed toward the implementation of an ELF shore-ship radio communication system.

r - -

Fig. 1. Site Alpha (in use 1962-1970).

TABLE I

Early Sanguine Chronology

1955

1958

1959

1960

1961

1962

1963

Polaris Special Projects Office established.

First Nicholas C. Christofilos ELF concept (August). Industrial briefings for new communication systems.

PANGLOSS starts at RCA. Institute of Defense Analysis conference on Christofilos concept (June).

Jim Creek 600 to 4000-Hz propagation experiment. Baker-Wagner measurements of earth-ionosphere cavity resonance (June). Second Nicholas C. Christofilos ELF concept (August).

Ad hoc ELF committee makes its decisive experiment recommendation (May). Decisive experiment implementation starts.

DECO ONR-sponsored ELF propagation experiment, using 60-Hz power line; reception at 1500 km (June- August). Sanguine decisive experiment ELF system operative (December).

Intensive Test measurements (January-April).

Intensive Test report completed (April 17). Intensive Test a t sea measurements (January-February).

Three receivers, each with an integration time of 5 min, were constructed to use in fixed, in land-portable, and in submarine installations. The data collected during the Intensive Test resulted in further validation of the zero-order-mode propagation model a t frequencies below 600 Hz and provided accurate attenuation data down to 78 Hz. Fig. 2 presents the various Intensive Test site locations.

In addition to the propagation investigations, six weeks of communication tests (starting January 21, 1963) were made with a receiver installed on the USS SEAWOLF (SSN-57.5). The submarine was equipped with a 1000-ft trailing cable, at the end of which was an electric probe-

MERRILL: HISTORICAL ASPECTS OF PROJECT SANGUINE 363

Fig. 2. Intensive Test site locations.

pair sensor with a 75-m probe separation. Signals a t 78, 125, 156, and 250 Hz were measured a t ranges up to 3200 km with the trailing antenna a t keel depth. Signals were received a t a range of 850 km with the antenna at greater depths. The power radiated from the experimental transmitting antenna was of the order of 1 W.

Table I lists some of the key events that led to this successful demonstration of the feasibility of ELF trans- mission from CONUS to a submarine at an operational depth, speed, and range.

PRESENT STATUS Project Sanguine is now in the Validation Phase of its

implementation. This current phase of the Navy program for implementing the ELF system will result, in 1975, in a competitively derived system design suitable for entry into prototype development.

REFERENCES [I] J. R. Wait, “The Sanguine concept,” in 1976 Ocean ZEEE Znt.

Conf. Eng. in Ocean Environment, IEEE Publication 72 CHO

[2] A. N. Soy,merfeld, “The propagation of waves in wireless telegraphy, Ann. Phys., vol. 81, pp. 1135-1153, 1926.

[3] H. H. Beverage, C. W. Rice, and E. Mr. Kellogg, “The wave antenna; A new type of highly directive antenna,” AZEE

[4] W. 0. Schumann, “On the electrical oscillations of the cavity Trans., vol. 42, pp. 215-266, Feb. 1923.

space earth-air-ionosphere excited by lightning strokes,” 2. Angew. Phys., vol. 9, p. 373, 1957.

[5] F. W. Chapman and R. C. V. Macario, “Propagation of audio- frequency waves to great distances,” Nature, vol. 177, p. 930, 1956.

[6] A. G. Jean, A. C. Murphy, J. R. Wait, and D. F. Wasmundt, “Observed attenuation rates of e.1.f. radio waves,” J . Res. Nat. Bur. Stand., vol. 65D (radio prop.), pp. 475-479, 1961.

660-1 OCC, Sept. 1972, pp. 84-87.

[7] J. R. Wait, “Mode theory and the propagation of ELF radio waves,” J . Res. Nut. Bur. Stand., vol. 64D, pp. 387-404, 1961.

[SI J. Galejs, “ELF waves in the presence of exponential ion- ospheric conductivity profiles,’’ I R E Trans. Antennas Propag.,

[9] J. R. Wait, Electromagnetic Waves in Stratified Media. Oxford: vol. AP-9, pp. 554-562, Nov. 1961.

[lo] J. Galejs, Terrestrial Propagation of Long Electromagnetic Waves. Pergamon, 1st ed., 1962; 2nd ed., 1970.

[Ill M. ,Baker and C. Wagner, “Observations of earth-ionosphere Oxford: Pergamon, 1972.

cavity resonances,” Nature, vol. 188, pp. 638-641, Nov. 1960.

Groton, Conn. Othc :r

John Merrill was born in Buffalo, N. Y . , on February 12, 1917. He received the B.A. and M.Ed. degrees from Hillyer College of the University of Hartford, Hartford, Conn., in 1953 and 1956, respectively. He also studied engineering at the University of Connecticut, Storrs, and the University of Buffalo, Buffalo, N. Y.

From 1944 to 1951, he was an Instructor in Electronics at the U. S. Coast Guard Radio Engineering and Maintenance School, teachinn affiliations have included the De-

partment of Electrical Engineering of the University of Buffalo, Hillyer College, Mitchell College, and the Ward School of Elec- tronics, Hartford, Conn. He was an Electronics Scientist in the Electromagnetics Division of the U. S. Navy Underwater Sound Laboratory, New London, Conn., from 1954 to 1959. His work was primarily concerned with UHF and microwave antenna develop- ment. He was a Staff Member and Project Director a t the Research Division of Radiation, Inc., Orlando, Fla., from 1959 to 1960. He returned to the Underwater Sound Laboratory in 1960 as a Senior Project Engineer, investigating phenomena in the VLF spectrum. In 1967, he was appointed Program Manager for the Laboratory’s Sanguine effort, a position he currently holds.

Mr. Merrill is a member of Phi Delta Kappa and was chairman of the Connecticut Valley Section, IRE, from 1952 to 1953.