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      <h3>
	Beyond the Cuban Missile Crisis</h3>
<p>
	The Cuban missile crisis is the best-known example of narrowly avoiding nuclear war. However, there are at least four other less well-known incidents in which the superpowers geared up for nuclear annihilation. Those incidents differed from the Cuban missile crisis in a significant way: They occurred when either the U.S. or Soviet or Russian leaders had to respond to false alarms from nuclear warning systems that malfunctioned or misinterpreted benign events.</p>
<p>

            <figure class="richtext-image full-width"><img alt="TOPOL M, in a test firing" class="richtext-image full-width" height="290" width="507"
            src="https://www.pbs.org/wgbh/nova/media/images/nuclear-false-alarms-01.width-800.jpg"/><figcaption>In the past quarter century, Russia and the U.S. each have come close twice to launching nuclear missiles like this Russian ICBM to counter a perceived attack.<div class="credit">&copy; WGBH Educational Foundation</div></figcaption>
            </figure>
            </p>
<p>
	All four incidents were very brief, probably lasting less than 10 minutes each. Professional military officers managed most of them. Those officers had to decide whether or not to recommend launching a "retaliatory" strike before possibly losing their own nuclear first strikes. In three of the four incidents, the decision not to respond to the alarm was made when space-based early-warning sensors failed to show signs of massive nuclear attacks. The fourth incident was caused by an inadequate early-warning satellite system that was fooled into thinking that reflected sunlight was the flames from a handful of ICBMs.</p>
<blockquote>
	Russia was poised, for a few moments at least, to launch a full-scale nuclear attack on the United States.</blockquote>
<p>
	As the following brief history of those four incidents makes clear, space-based early-warning systems played a major role in avoiding nuclear war. During the 1980s, a few specialized articles in the media hinted at the presence of those systems. However, it was only during the Gulf War that the American public truly became aware of U.S. capability to detect missile launches using space-based assets. During that crisis, U.S. Defense Support Program (DSP) satellites, first orbited in 1970, detected the launch of every Iraqi Scud missile. The satellites made the detections from their orbits by "seeing" the infrared light that the missiles' motors gave off during powered flight. The warning of launches was transmitted to Patriot air defense missile batteries in Israel and Saudi Arabia to support attempts to shoot down the incoming warheads.</p>
<p>
	The association with the fighting of conventional war has obscured the more important strategic role those systems have played: reassuring leaders of the United States and Russia that they were not under nuclear attack. A review of the four nuclear crises will better highlight that role.</p>
<h3>
	The training tape incident</h3>
<p>
	Shortly before 9 a.m. on November 9, 1979, the computers at North American Aerospace Defense Command's Cheyenne Mountain site, the Pentagon's National Military Command Center, and the Alternate National Military Command Center in Fort Ritchie, Maryland, all showed what the United States feared most—a massive Soviet nuclear strike aimed at destroying the U.S. command system and nuclear forces. A threat assessment conference, involving senior officers at all three command posts, was convened immediately. Launch control centers for Minuteman missiles, buried deep below the prairie grass in the American West, received preliminary warning that the United States was under a massive nuclear attack.</p>
<p>

            <figure class="richtext-image full-width"><img alt="American Minuteman missile" class="richtext-image full-width" height="471" width="434"
            src="https://www.pbs.org/wgbh/nova/media/images/nuclear-false-alarms-02.width-800.jpg"/><figcaption>Minuteman missiles similar to this one, shown in a test firing from Cape Kennedy, Florida, could deliver a nuclear payload as far as 8,000 miles away. 
<div class="credit">AP Photo/Jim Kerlin</div></figcaption>
            </figure>
            </p>
<p>
	The alert did not stop with the U.S. ICBM force. The entire continental air defense interceptor force was put on alert, and at least 10 fighters took off. Furthermore, the National Emergency Airborne Command Post, the president's "doomsday plane," was also launched, but without the president on board. It was later determined that a realistic training tape had been inadvertently inserted into the computer running the nation's early-warning programs.</p>
<p>
	However, within minutes of the original alert, the officers had reviewed the raw data from the DSP satellites and checked with the early-warning radars ringing the country. The radars were capable of spotting missiles launched from submarines close to the U.S. shores and ICBM warheads that had traveled far enough along their trajectories to rise above the curvature of the Earth. The DSP satellites were capable of detecting the launches of Soviet missiles almost anywhere on the Earth's surface. Neither system showed any signs that the country was under attack, so the alert was canceled.</p>
<p>

            <figure class="richtext-image full-width"><img alt="missle launch" class="richtext-image full-width" height="424" width="652"
            src="https://www.pbs.org/wgbh/nova/media/images/nuclear-false-alarms-03.width-800.jpg"/><figcaption>In the "training tape" incident, Defense Support Program early-warning satellites saved the day. Pictured is a DSP satellite going aloft in April 2003.<div class="credit">Courtesy Lockheed Martin</div></figcaption>
            </figure>
            </p>
<h3>
	The computer chip incident</h3>
<p>
	On June 3, 1980, less than a year after the incident involving the training tape, U.S. command posts received another warning that the Soviet Union had launched a nuclear strike. As in the earlier episode, launch crews for Minuteman missiles were given preliminary launch warnings, and bomber crews manned their aircraft. This time, however, the displays did not present a recognizable or even a consistent attack pattern as they had during the training tape episode. Instead, the displays showed a seemingly random number of attacking missiles. The displays would show that two missiles had been launched, then zero missiles, and then 200 missiles. Furthermore, the numbers of attacking missiles displayed in the different command posts did not always agree.</p>
<p>
	Although many officers did not take this event as seriously as the incident of the previous November, the threat assessment conference still convened to evaluate the possibility that the attack was real. Again the committee reviewed the raw data from the early-warning systems and found that no missiles had been launched. Later investigations showed that a single computer chip failure had caused random numbers of attacking missiles to be displayed.</p>
<h3>
	The autumn equinox incident</h3>
<p>
	On September 26, 1983, the newly inaugurated Soviet early-warning satellite system caused a nuclear false alarm. Like the United States, the Soviet Union realized the importance of monitoring the actual launch of ICBMs. However, the Soviets chose a different method of spotting missile launches. Instead of looking down on the entire Earth's surface the way U.S. DSP satellites do, Soviet satellites looked at the edge of the Earth—thus reducing the chance that naturally occurring phenomena would look like missile launches. Missiles, when they had risen five or ten miles, would appear silhouetted against the black background of space. Furthermore, when the edge of the Earth is viewed, light reflected from clouds or snow banks has to pass through a considerable amount of the atmosphere. That view reduces the chances that clouds and snow may cause false alarms.</p>
<p>
	A satellite has to be in a unique position to view a recently launched missile silhouetted against the black of space. To get that view, the Soviet Union picked a special type of orbit that it had used for its communications satellites. Those orbits, known as Molnyia orbits, come very close to the Earth in the Southern Hemisphere but extend nearly a tenth of the distance to the moon as the satellite passes over the Northern Hemisphere. From that position high above northern Europe, the Soviet Union's Oko ("Eye") early-warning satellites spend a large fraction of their time viewing the continental U.S. missile fields at just the right glancing angle. However, shortly after midnight Moscow time on September 26, 1983, the sun, the satellite, and U.S. missile fields all lined up in such a way as to maximize the sunlight reflected from high-altitude clouds.</p>
<p>

            <figure class="richtext-image full-width"><img alt="orbit diagram" class="richtext-image full-width" height="480" width="429"
            src="https://www.pbs.org/wgbh/nova/media/images/nuclear-false-alarms-04.width-800.jpg"/><figcaption>A Russian Oko early-warning satellite's hypothesized view of U.S. missile fields at the time of the so-called "autumn equinox" incident<div class="credit">Geoffrey Forden, MIT</div></figcaption>
            </figure>
            </p>
<p>
	Whether that effect was a totally unexpected phenomenon is hard to know. That may have been the first time this rare alignment had occurred since the system became operational the previous year. Press interviews with Lt. Col. Stanislav Petrov, the officer in charge of Serpukhov-15, the secret bunker from which the Soviet Union monitored its early-warning satellites, indicated that the new system reported the launch of several missiles from the U.S. continental missile fields. Petrov had been told repeatedly that the United States would launch a massive nuclear strike designed to overwhelm Soviet forces in a single strike.</p>
<p>
	Why did that false alarm fail to trigger a nuclear war? Perhaps the Russian command did not want to start a war on the basis of data from a new and unique system. On the other hand, if the sun glint had caused the system to report hundreds of missile launches, then the Soviet Union might have mistakenly launched its missiles. Petrov said that he refused to pass the alert to his superiors because "when people start a war, they don't start it with only five missiles. You can do little damage with just five missiles."</p>
<h3>
	The Norwegian rocket incident</h3>
<p>
	Early on the morning of January 25, 1995, Norwegian scientists and their American colleagues launched the largest sounding rocket ever from Andoya Island off the coast of Norway. [Sounding rockets collect data on atmospheric conditions from various altitudes.] Designed to study the northern lights, the rocket followed a trajectory to nearly 930 miles altitude but away from the Russian Federation. To Russian radar technicians, the flight appeared similar to one that a U.S. Trident missile would take to blind Russian radars by detonating a nuclear warhead high in the atmosphere.</p>
<p>

            <figure class="richtext-image full-width"><img alt="diagram" class="richtext-image full-width" height="247" width="516"
            src="https://www.pbs.org/wgbh/nova/media/images/nuclear-false-alarms-05.width-800.jpg"/><figcaption>The trajectory of the Black Brant XII sounding rocket, which triggered the "Norwegian rocket" incident<div class="credit">Geoffrey Forden, MIT</div></figcaption>
            </figure>
            </p>
<p>
	That scientific rocket caused a dangerous moment in the nuclear age. Russia was poised, for a few moments at least, to launch a full-scale nuclear attack on the United States. In fact, President Boris Yeltsin stated the next day that he had activated his "nuclear football"—a device that allows the Russian president to communicate with his top military advisers and review the situation online—for the first time.</p>
<p>
	However, we can be fairly confident that Yeltsin's football showed that Russia was not under attack and that the Russian early-warning system was functioning perfectly. In addition to the string of radars surrounding the border of the former Soviet Union, Russia had inherited a complete fleet of early-warning satellites that, even by 1995, still maintained continuous 24-hour coverage of the U.S. continental missile fields. In the early 1990s Russia had still managed to launch replacement satellites for its early-warning system as the previous ones died out—thereby retaining continuous coverage. Because of those satellites, Yeltsin's display must have shown that no massive attack was lurking just below the horizon.</p>
<h3>
	Towards reliable early warning</h3>
<p>
	The danger posed by those incidents was not the unauthorized or accidental launch of a handful of nuclear-tipped missiles but the possibility that either country might misinterpret a benign event—a computer training tape mistakenly inserted into an operational computer or sunlight glinting off clouds during a rare lineup of the sun, Earth, and satellite—and decide to launch a full-scale nuclear attack.</p>
<p>
	Each incident caused officials to take steps to solve a specific problem. After the training tape incident, the U.S. Department of Defense constructed a separate facility to train operators so that a training tape could not again be inserted into the computer running the nation's early-warning system. Apparently, the Soviet Union launched a new fleet of early-warning satellites into geostationary orbit simply to provide a second angle from which to view U.S. missile fields. That expensive and redundant system ensured that at least one satellite could search for missile launches free from sun glint.</p>
<blockquote>
	Despite measures taken to prevent them, such accidents are inevitable.</blockquote>
<p>
	After three of the four incidents, the U.S. government maintained that steps were taken that would prevent any future false alarms. However, it had to wait only seven months after the first incident (the computer tape incident) to see that complex organizations, relying on even more complex machinery, can find new and unexpected ways to fail. In fact, a comprehensive study of nuclear accidents has shown convincing historical evidence that, despite measures taken to prevent them, such accidents are inevitable.</p>
<p>
	The most recent example of solving the "last problem" was the Clinton administration's initiative to share early-warning data with Russia. The jointly manned center has been presented by the American side as a solution to the decline of Russia's early-warning facilities. Russians familiar with the negotiations, however, maintain that the center has no military significance. That view is underscored by the choice of the site for the center: an old schoolhouse nearly an hour away from downtown Moscow. In fact, U.S. Department of Defense officials familiar with the Joint Data Exchange Center (JDEC) admit that, even if the center had been active during the Norwegian rocket incident, its only effect would have been to facilitate the launch notification issued before the NASA launch.</p>
<p>
	Any assistance the United States provides must increase Russia's confidence in the validity of its own early-warning systems. The JDEC fails that test. Russia would never believe that the United States would pass along launch indications if a U.S. nuclear attack had been launched.</p>

  



Russia and the U.S. have both come harrowingly close to launching nuclear missiles in response to a perceived attack.


Dr. Geoffrey Forden

Articles

False Alarms in the Nuclear Age