by DAVID KAHN
The end link consists of a 3 × 5-inch card, sealed in clear plastic and framed in metal, which the two launch control officers wear on chains around their necks. They are forbidden to take them off while they are on duty in their concrete missile-control capsule deep underground. The message to go to war would come over the red telephone of the Primary Alert System, which rings with a high, warbling whippoorwill tone, in a crackly voice reciting letters in the phonetic alphabet: “TANGO MIKE PAPA YANKEE ROMEO …,” with a monotone “Break, break” after each group of five. Both officers must take down the message, decode it individually, and confirm each other’s reading before commencing the countdown.
Further codes give the “Go” signal in the fail-safe system to manned airplanes. Should the alert be sounded, jet bombers of the Strategic Air Command would immediately streak toward preassigned targets. But they may not pass a certain point—the “fail-safe” point—until they receive positive instructions. The code for these instructions is kept in the “red box”—actually a belge box with a bright red door about 18 inches square on the wall of the S.A.C. headquarters at Offutt Air Force Base and in the flying command posts. It is changed at random intervals. The headquarters controller would remove the code documents, each covering a different contingency, from their sealed X-rayproof “unique device.” The information, fitted into the proper context, is radioed to the planes, preceded by verification and acknowledgment. “They have separate pieces of the pie, and we have the whole pie,” said an S.A.C. senior controller. “Until we send out the whole pie, their pieces mean nothing.” Three members of each crew must individually copy down the go-to-war message, match this “whole pie” to the slices that each one carries, and agree with the others that it is the real thing. Only then, according to the system, can they “go.” This is part of the overall control that, President Johnson has said, the nation has imposed to prevent accidental war. In it, COMSEC plays a vital role.
Far and away the largest of N.S.A.’s three operating branches is the Office of Production, or PROD, with a little more than half of N.S.A.’s entire headquarters personnel. What PROD produces is communications intelligence. The term must be taken in the broadest possible sense. For although it includes cryptanalysis, traffic analysis, and analysis of cleartext traffic, it is not confined to studies of man talking to man. Communications intelligence in the Cold War includes machines talking to machines—the self-interrogations of radars, the remote-control systems of guided missiles, the telemetry of artificial satellites, the I.F.F. or identification-friend-or-foe systems. All these are communications devices, usually radios modified in one way or another, and a great deal can be learned from their location and operation. N.S.A. entered this electronic field in the 1950s, and began monitoring Soviet missiles in 1958, the year after Sputnik, largely due to the initiative of PROD’S Joseph P. Burke, a former traffic analyst.
PROD is always headed by a military man. The deputy at one time was Abraham Sinkov, one of Friedman’s original three assistants. For many years the office was divided into eight sections. Four handled cryptanalysis and associated traffic analysis. ADVA (for “ADVAnced”) attacked high-level Soviet cipher systems and diplomatic codes. GENS (for “GENeral Soviet”) attacked Soviet military code systems and medium-level ciphers; its chief at one time was Francis A. Raven, who recovered the key-pattern of the Japanese PURPLE machine in 1941. ACOM (“Asian COMmunist”) attacked the code and cipher systems of those nations, and ALLO (“ALL Others”) attacked the cryptosystems of neutrals, Communist satellites, and the nations of the free world. A section called MPRO (“Machine PROcessing”) provided computer services to the cryptanalysts. The section called Communications handled the intercept organization. The two other sections may have analyzed clear-text intercepts and studied the electronic material.
After Martin and Mitchell exposed this arrangement, however, PROD was reorganized into three big sections. These were set up on a geographical basis, and each analyzes all communications within its area, from human clear text to coded mechanical “messages.”
To gather the raw material for these sections, N.S.A. and the armed forces have cast a fine-meshed net over the world of electrical communications. Around the globe they have spotted more than 2,000 intercept positions (one man listening at one radio set). Most are on U.S. military bases overseas, but some are on planes or aboard ship. More than 8,000 soldiers, sailors, and airmen, accompanied and supervised by N.S.A. personnel, type out on four-ply paper the Morse code messages that peep incessantly in their earphones. Other personnel tend the equipment that intercepts radioteletype messages and the tape-recorders for voice communications. Still others forward the intercepts to Fort Meade. Interception goes on around the clock, at every wavelength, for every audible transmission, of every single country.
American electronic reconnaissance is carried out mainly by airplane. “Ferret” airplanes patrol the vast edges drear of the Communist world. Their guts are packed with complicated electronic gear for the use of their electronic specialists, called “ravens,” in recording and analyzing radar signals. The ferret receivers pose interesting problems in design. On the one hand, they must be able to accept unexpected signals emitted by new Soviet radars. On the other hand, they must be able to measure the radar’s pulse rate and its frequency with great precision. Ideally, they should always be ready to accept another signal and not dwell too long on the signal passing through their circuits. Since no one receiver can perform all these functions, the ferrets must carry many types of receivers. In addition to simply picking up the signals, the ravens try to locate their source: it is obviously more valuable to know that six new radars are operating around a region north of Moscow than just somewhere in Russia.
All signals are not always heard. The ferrets may not be in range. The ravens may not be operating the right equipment. The Russians may have turned some radars off so as not to show all their cards. To tease one another into turning on some of their silent and probably special ones, nations could direct a squadron of bombers at the enemy’s territory on a mock raid. One can imagine the flurry of electronic activity that would be created if a dozen Soviet bombers headed toward the United States. Though this dangerous game is not played by the two great powers, a modification of it is. Individual six-jet RB-47 ferrets fly dangerously close to the Soviet frontiers and sometimes actually cross them—though such practices are of course denied by the United States government. Russian fighters and antiaircraft rockets attack and sometimes down them. Thus international incidents result.
Such was the case of the RB-47 shot down on July 1, 1960, in the arctic waters of the Barents Sea, killing four of its six-man crew. The Soviet Union protested in the United Nations that the aircraft had violated Russia’s territorial rights—a charge that the United States denied. Later the newly elected President Kennedy negotiated the release of navigator Captain John McKone and co-pilot Captain Bruce Olmstead. Perhaps the best-known penetration flight of all was that of Francis Gary Powers, whose U-2, like all those that had preceded his, carried “black boxes” that recorded Soviet radar signals on magnetic tape for analysis by N.S.A.
The Soviets engage in electronic reconnaissance, too. They send their TU-16 Badgers day after day against the American radar picket fence in Canada’s far north called the DEW (Distant Early Warning) Line. They depend more heavily, however, upon their trawlers. Most of the 3,000 ships of Russia’s fishing fleet that regularly ply the waters of the North Atlantic are legitimate, but almost 90 during some major American exercises in 1961 were getting their best catch from the airwaves. The trawlers often roam the fish-poor but intelligence-rich waters off Cape Kennedy. Before a missile firing, tracking and guidance radars must be checked, communication links tested, telemetry circuits energized. All these give the Russian eavesdroppers a good picture of what is going on. The trawlers also lurk near the Army signal center at Fort Monmouth, New Jersey. Their appearance off the New England coast once caused a slowdown of experimen
tal radar tests at M.I.T.’s Lincoln Laboratory in Lexington, Massachusetts.
The most sophisticated and most secret reconnaissance and intercept tools that serve N.S.A. are the satellites that eavesdrop upon communications. These are a subseries in the SAMOS (for “Satellite And Missile Observation System”) satellites, other subseries of which photograph and televise the pictures of missile bases, encampments, and the like. The ferret satellite hears the faint whisperings of Communist radios and radars as it orbits high over the windy steppes. Its sensors, developed by Lockheed Aircraft Corporation and R.C.A., can tap microwave telephone links and can pick up the radio guidance signals of missile launch sites. When commanded by a signal from the ground, its tape recorders spew out these signals in what is probably an incredibly compressed spurt of information to a waiting ground station. With the attached second-stage Agena rocket, SAMOS satellites stand 22 feet tall and 5 feet in diameter; they weigh 4,100 pounds, and circle the globe upright like a giant cigar, carrying a 300-to-400-pound instrument package. The Soviets have their own COSMOS spy satellite, which probably includes a ferret series.
The information collected by ferrets constitutes electronic intelligence. The detection of a cluster of radars in a remote part of Siberia may indicate the presence of a Soviet rocket base. The operating parameters of a radar—its “electronic signature”—can disclose its function—a search, height-finder, or target-guidance radar, for example. Analysis of Russian telemetry signals may yield important details about rocket instrumentation. But most of this electronic intelligence is studied to find ways of thwarting Soviet radars that would detect and locate U.S. bombers or missiles and direct their destruction. These ways are called electronic countermeasures, or E.C.M.’s. The electronic security that defends against enemy E.C.M.’s comprises emission security, which defends against electronic reconnaissance, and electronic counter-countermeasures, or E.C.C.M. ’s. In operation, E.C.M.’s and E.C.C.M. ’s are so intimately intertwined and mutually reliant that the whole field of electronic security and electronic intelligence is usually considered under the general heading of “electronic warfare.”
Electronic warfare began in World War II, when radar itself first emerged; in fact, the astonishing employment of electronics is one of the most notable features of that struggle. Winston Churchill, who was intimately involved with the warfare of these invisible radiations during the Battle of Britain, gave it the grandiloquent name of “The Wizard War.” “This was a secret war,” he wrote, “whose battles were lost or won unknown to the public, and only with difficulty comprehended, even now, by those outside the small high scientific circles concerned. No such warfare had ever been waged by mortal men.” It was vital. “Unless British science had proved superior to German, and unless its strange sinister resources had been effectively brought to bear on the struggle for survival, we might well have been defeated, and, being defeated, destroyed.” One of its battles was that of the KNICKBEIN, a German navigational beam whose two sections crossed over British cities and which the British scientists twisted so that the Luftwaffe bombers unloaded most of their high explosive during the Battle of Britain into empty fields and the Channel.
Later the British carried the Wizard War to the enemy. Radar, of course, operates by emitting pulses of radio energy which bounce off objects, such as airplanes, and return to the radar unit. The direction from which these echoes come gives the location of the object. And since radio waves travel at the constant speed of light, the radar unit can determine the distance of the object by measuring the interval between the transmission of the radar pulse and the reception of its echo. The British soon discovered that a strip of metal cut to half the length of a radar wavelength would return a much stronger echo than an untuned mass of metal, such as an aircraft. If these strips were dropped like chaff from airplanes, they would form an electronic smokescreen behind which British bombers could dispense death and destruction undisturbed by German night fighters and antiaircraft fire. Britain first tried this chaff, codenamed WINDOW, in a raid on Hamburg July 24, 1943. “Its effects surpassed expectations,” Churchill said. “For some months our bomber losses dropped to nearly half.”
After the war, as aircraft flew faster and guided missiles became common, radar, which alone could give sufficient warning of an attack, became increasingly important. So, then, did electronic warfare. Three technical developments intensified it: the transistor, which greatly lightened the reconnaissance equipment, giving planes greater range and allowing additional and more sensitive equipment to be carried; the traveling wave tube, which permitted rapid tuning over a broad frequency band; and the maser, which vastly increased receiver sensitivity. Today electronic warfare accounts for most of the huge defense electronics industry and costs the taxpayers well over half a billion dollars a year for research, development, and production—to say nothing of the operation of the equipment.
The tape recordings and the photographs of cathode-ray tubes that the ferrets bring back are subject in N.S.A. to intense analysis. This determines such radar operating parameters as frequency, type of modulation, pulse rate, pulse shape, power, type of scan, antenna rotation rate, and polarization. This information enables engineers to design techniques to blind or trick enemy radars.
The earliest and simplest E.C.M. was chaff. Modern radars winnow it out without much difficulty, largely because airplanes fly much faster than the drifting cloud of metal strips. To counter this, bombers fire rockets packed with chaff to explode well ahead of them to confuse the radars. Another E.C.M. uses decoys that enhance the radar echo, thus make the decoys appear larger on the radar scope than they really are, and so trick the operator into tracking them instead of the real bombers. One such device is the corner reflector. Its three metal plates are set at right angles to one another, and the corner formed by them returns a stronger echo than a flat surface. Another device is the Luneberg lens, a sphere that focuses a lot of radar energy onto a small surface that reflects it all back. One lens of 12 inches diameter produces a radar echo equivalent to a target with a cross section of 700 square feet. A swarm of them on decoy “penetration aids” accompanying an intercontinental ballistic missile could swamp out the enemy radar defense, making it almost impossible for it to discriminate the warhead and direct its antimissile missiles against it.
Diametrically opposed to the decoy technique are the materials that make an object invisible to radar. One kind is a two-and-a-half-inch thick sandwich of foam plastic. It absorbs and dissipates the radar energy, somewhat in the way that soundproofing material works. Since missiles can hardly be encased in this spongy material, they may use a special ceramic whose inner surface is lined with the radar-absorbent stuff.
These are all passive countermeasures. Active E.C.M.’s become much more sophisticated, although the simplest is crude—jamming. Jamming has the great advantage of disrupting much radar function. It does not require very much power, since the radar echo is so weak that it takes very little effort to overcome it. Modern radars can defeat jamming to an extent, however, by the E.C.C.M. called “integration.” The returns from several sweeps of the radar beam are piled up on the scope until eventually the combined pips from the target become strong enough to stand out even against the background of noise. Jamming’s real disadvantage is that it often disrupts one’s own radars and radios and prevents interception of valuable enemy communications.
Another active E.C.M., the multiple-target generator, emits many fake returns. On the scope of the enemy radar will appear a whole flock of blips, confusing the operator, who will not be able to pick out the true return from the many false ones. A third active E.C.M. forces a precision radar that has locked on to a target to “de-acquire” it. The target transmits a false timing signal that disrupts the radar’s function and prevents it from tracking him.
These three active E.C.M.’s are confusion techniques. They have the disadvantage that the enemy knows he is being confused. Subtlest of all E.C.M.’s are the deception te
chniques, which trick the enemy without his being aware of it. These usually rely upon two radar characteristics—that a target will sense that it is being “illuminated” by a radar long before the echoes are strong enough to return to the radar, and that radars usually follow the strongest echo. One deception technique sends out a strong fake echo timed to reach the radar earlier or later than the true echo. The radar will thus show a target much nearer or farther from it than the attackers really are. Another technique produces a false target moving at a false speed on the radar scope. Radars that depend on a Doppler shift to determine target speed can be tricked by E.C.M.’s that adjust their frequencies to indicate a false Doppler shift, showing a target moving more slowly than the real one is, or perhaps not moving at all.
Fighting these techniques are emission security and electronic counter-countermeasures, or E.C.C.M.’s. Radars can be made to respond only to a particular wave shape. They can shift frequency rapidly and irregularly, or change their pulse rates unpredictably. These constitute a kind of electronic code which the attackers would have to break. Electronic warfare has even invaded the infrared. Antimissile missiles that home in on their targets by the heat of the exhaust can be decoyed by extremely hot flares.
In an actual strike, a B-58 loaded with countermeasures equipment instead of explosives will convoy the attacking bombers to fight off the enemy with electronic bullets. The electronic warfare officer decides when to fire the varied weapons at his disposal. As he approaches the enemy radar limits and senses its illumination, he emits false range and speed data. With closer penetration, he launches chaff rockets and reflectors and generates multiple targets to deny information to the enemy. As the squadron nears the target area, he busily eyeballs his scopes and listens in his earphones for signal characteristics indicating that the precision radars have locked on to him. When they do, he pulls every trick in the book to nullify their threat. After determining their frequencies and pulse rates, he confuses the missile-control radars and jamstheir instructions to their missiles. He sends out small but big-looking decoys. In a few hectic minutes he must shelter his squadron under an impervious electronic canopy and shield it from the enemy radiations that can be as lethal to his mates as death rays. Upon him may rest the very success or failure of the mission.