The Secret of Plesetsk

A short train ride from London, in Britain's dreary industrial Midlands, the town of Kettering was long distinguished solely for its output of inexpensive shoes, produced by the millions at local factories. Now the town has won new honors. Using makeshift equipment, a physics teacher and a group of bright high school boys at Kettering Grammar School have discovered the location of a new and previously unannounced rocket-launching site in Russia.

Kettering's senior physics master, Geoffrey Perry, began to suspect the existence of a new Russian launch site last March after his teen-age students recorded signals from the newly launched Cosmos 112 reconnaissance satellite and plotted its orbit. Instead of being inclined to the equator at 65DEG--the inclination angle of earlier Cosmos orbits--112's orbital path had an angle of 72DEG. Also, the satellite had been launched at a later time of day than previous Cosmos shots and had returned to earth after 122 revolutions, instead of the usual 124. In a letter to the Brit ish magazine Flight International, Perry reported that Cosmos 112 could not have been launched from either Tyuratam or Kapustin Yar, the two known Russian launch sites, both of which are in the southern part of the Soviet Union. Instead, he suggested, it had been launched from a more northerly site--perhaps the southernmost tip of Novaya Zemlya, an island in the Barents Sea.

Two later Cosmos shots, 114 and 121, had orbits inclined at 73DEG, strengthening Perry's belief that rockets were being launched from a new site. But their paths were too nearly parallel to Cosmos 112's to calculate precisely where their initial orbits all intersected over Russia -- which would be the location of the launch site. The Russians themselves provided the needed data in October with the flight of Cosmos 129. Though its orbital inclination was 64.57DEG, it was launched later in the day than typical 65DEG Cosmos satellites and landed only 6 3/4 days later, instead of the usual eight.

63DEG North, 41DEG East. Using a computer belonging to a Kettering firm, Perry quickly confirmed that Cosmos 129 had also been launched from a new site. With his students, he plotted its orbital path and determined that it intersected the others at 63DEG north latitude and 41DEG east longitude, a point near the town of Plesetsk, about 140 miles south of the White Sea port of Archangel. It was from this site, he was convinced, that all four of the mysterious Cosmos satellites had been launched. Though neither Russia nor any U.S. Government source has officially confirmed existence of the new launch site, the U.S. has known of its existence for months. Noting that the new base is astride one of the paths that U.S. missiles could follow in an attack on Russia, Aviation Week speculated last week that it might be intended primarily as a launch site for long-range Russian anti-missile missiles.

Perry and his students use only rudimentary devices to listen in on satellites: a 24-ft. dipole antenna strung between two school buildings, a $70 war-surplus radio receiver, a surplus radio-frequency-signal generator, a tape recorder, a small world globe and a desk calculator. To produce an audible tone from the 20-megacycle Cosmos telemetry picked up by their receiver, they combine it with the output of the signal generator.

Because of the Doppler effect, the resulting tone decreases steadily in pitch, or frequency, as a satellite approaches and passes beyond the Kettering antenna. At the moment that the satellite reaches its point of closest approach the frequency of the tone becomes identical with the difference between the frequencies of the satellite transmitter and the signal generator. By recording the closest approach time on successive days, determining when Russian controllers turn on satellite transmitters, and noting when signals suddenly change pitch (during the firing of retrorockets) or are permanently silenced, there is little that Perry and his students cannot deduce about a satellite's origin, orbit and landing site.

22 1/2DEG Miss. Even their latest coup, the Kettering boys had a list of impressive accomplishments, many of which were reported in modest letters to British science publications. In 1964, Perry predicted re-entry time for Cosmos 32 more accurately than did NASA's sophisticated space-tracking network. Before the Russians announced the launch of the three-man Voskhod 1, and before it was detected by the mighty Jodrell Bank radio telescope, Perry blandly telephoned word of the flight to the British space-tracking network. When Voskhod 2 returned to earth, the Kettering trackers calculated that it had landed some 22 1/2DEG in latitude or about 700 miles from its intended touchdown point; the Russians did not admit until a year later that the craft had landed far from its intended target.

Perry originally established Kettering's space-tracking project to demonstrate the Doppler effect to his physics class. Its purpose nowadays is to help stimulate student interest in physics and mathematics. "When you talk space and rockets to these kids," he explains, "they listen." But the teacher clearly enjoys the project just as much as the youngsters. He proudly allows visitors to riffle through pictures of satellites photographed as they passed over the school grounds, then plays tapes of telemetry signals and voice conversations picked up from space on the Kettering receiver. His favorite is the voice of Lady Astronaut Valentina Tereshkova calling "Seagull, over and out" to an entranced ground controller.

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