TELE-X - a Satellite System for TV and Data Communication ...

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60 Fig. 2 An example of the impact area of EMP from a high-altitude nuclear explosion over Europe EMP generation region (altitude 20- 40 km) Electrons in spiral paths along the earth's magnetic field The direction of propagation of the EMP field The earth s magnetic field The EMP impact area at ground level the same time circuit-breakers on the power lines started blowing like popcorn. Not a cloud in the sky, so lightning could not be blamed. The power company failed to trace any gigantic electrical surge able to blow out virtually the entire systems simultaneously. The mystery was solved later - then promptly sealed under a "top secret" stamp. The culprit: A high altitude nuclear test burst more than 500 miles away. More than twenty years have passed since then, and society has developed and changed in such a way that the nuclear EMP threat has grown. The development in electronics has gradually led from transistors to large and very largescale integrated circuits (LSI, VLSI) that work with low signal and power levels in the range 10~ 3 to 10 8 W per transistor. Susceptibility thresholds are increasing and the pulses and energy surges need not be very high in order to cause damage (junction burnout), only of the order of 10 3 to 10 6 J. At the same time society has become much more dependent on electronics. For example, telecommunication networks, high-voltage power supply networks, railway networks, air traffic, water supplies and process industries are all controlled and regulated by equipment which usually contains susceptible semiconductor components. The increasing anxiety about nuclear EMP has recently been mirrored in the increase in newspaper articles and TV reports on the subject. The greater vulnerability makes EMP attacks more attractive. It is quite possible that special EMP weapons already exist. An attacker could find it profitable to start military operations with an EMP attack. This would create such chaos that subsequent measures would be more effective and counter-offensives made more difficult. A high-altitude explosion can be triggered at a large distance from the borders of the country to be attacked and still have a great impact on that country. The country attacked might not even realize that a nuclear explosion had occurred, let alone who set it off. With a high-altitude explosion (at above 30 km) effects other than EMP could be negligible at ground level, and perhaps be impossible to detect without special equipment. Large sums have been invested in EMP protection. Ten years ago the US was spending over 250 M US$ a year on EMP protection and testing. In October 1981 president Reagan stated that the US defense project with the highest priority was not the MX system or the B1 bombers but "to strengthen and rebuild our communications and control systems -
Fig. 3 The electrical and magnetic EMP field from a high-altitude explosion, plane wave and horizontal polarization. The time dependency is generalized a much neglected factor in our strategic deterrent". 20 billion (10 9 ) US$ was earmarked for this project, a large part of which is intended for EMP hardening. In the Soviet Union EMP protection has even been provided for facilities of less than top priority for about 20 years. Telecommunication networks that still function after high-altitude explosions are vital if diplomatic and political communication between nations is to be possible so as to avoid the military escalation of a limited nuclear confrontation into a total nuclear war. In the case of a nuclear war elsewhere a country needs a working telecommunication network, partly in order to be able to collect and process weather and nuclear radiation reports It must be possible to inform the population of the country about the situation if chaos and exposure to nuclear radiation are to be limited. This could save many lives. Without a secure telecommunication network it would also be very difficult to rebuild and reconnect the country's electric power system before chaos arises and spreads. Disruption of electric power would seriously affect pumping of water and fuel supplies, and many other vital functions. The generation of nuclear EMP From a nuclear explosion an intense gamma radiation pulse propagates at the speed of light. The gamma radiation consists of photons (radiation quanta) which collide with air molecules or other matter and release free electrons. The so-called Compton electrons leave positively-charged ions behind and move on in the direction of propagation. They are slowed down by collisions, and each Compton electron thereby generates tens of thousands of secondary electron-ion pairs. The charge separation causes a strong electric field and the charging movements produce a current. For explosions close to the ground, conditions are strongly asymmetrical. There is a net electron current with a strong upward component from ground zero. Electrons travelling outward in the air from the burst return toward the burst point through higher-conductivity ground and ionized air paths. The current loops generate very large azimuthal magnetic fields. For exo-atmospheric explosions Compton electrons are not generated until the gamma rays that travel downward reach the denser atmospheric layers, at a height of 20 to 40km above ground. This is known as the deposition layer. The electrons encounter the earth's magnetic field and are deflected, producing a transverse electric current. This results in electromagnetic radiation which is directed radially out from the explosion point, adding in phase. This EMP has a tremendous coverage. In the case of large explosion yield, the higher frequency part of EMP extends to the horizon. The lower frequencies will follow along a duct between the earth and the bottom of the ionosphere as well as along the surface of the earth far behind the horizon. For example, with a height of burst of 100km, large parts of Europe could be covered (impact radius approximately 1200 km along the surface of the earth; 400 km altitude would give a radius of approximately 2200 km). The EMP effect would be noticeable even outside this area. Fig. 4 The spectrum of the electrical field and the corresponding normalized cumulative energy density of EMP from a high-altitude explosion Magnitude of the EMP The EMP from a high-altitude explosion consists of a plane wave (E/H = 377 ohms), which is propagated along the line of sight from the explosion point. The E and H fields are perpendicular to each other and to the direction of propagation. A part of the pulse is reflected by the ground, and the rest is propagated into the ground and is gradually attenuated. The strength and polarization of the field vary within the impact area due to various factors. Vulnerability and
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ERICSSON REVIEW Integrated Maintena
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ERICSSON REVIEW Number 1 1983 Volum
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The unique facility of a satellite
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Technical data for a station Antenn
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Technical data for the feeder link
Page 13 and 14: 9 Fig. 7 Mixer and preamplifier The
Page 15 and 16: MATS ENEBORG Fibre Optics and Line
Page 17 and 18: 13 Fig. 6 The structure of system Z
Page 19 and 20: 15 Fig. 9 Part of the junction netw
Page 21 and 22: Fig. 11 Part of an urban and trunk
Page 23 and 24: 19 MATS ENEBORG BJORN JOHANSEN Depa
Page 25 and 26: Fig. 6 An example of a printout of
Page 27 and 28: Technical data for ZAN 101 Maximum
Page 29 and 30: Fig. 14 The Transmission maintenanc
Page 31 and 32: 27 BJORN LENGQUIST PER AKE WIBERG E
Page 33 and 34: 29 Supervision of the digital inter
Page 35 and 36: 31 ules can be used to successively
Page 37 and 38: BENGTJANSSON KENT JOHANSSON TOMMY O
Page 39 and 40: 35 The control individuals are divi
Page 41 and 42: 37 Fig. 10 LPB 110 used in an AXE 1
Page 43 and 44: 39 BENGT LAGERSTEDT Public Telecomm
Page 45 and 46: 41 Fig. 6 With multiplexer ZAH 1.5/
Page 47 and 48: Fig. 10 In this example of the use
Page 49 and 50: 45 HARALD BRANDT ALEKSANDER MARLEVI
Page 51 and 52: 47 Fig. 5 Stored program controlled
Page 53 and 54: 49 quency jumps and no transmission
Page 55 and 56: Hotel Communication System Robert D
Page 57 and 58: 53 Fig. 3 The answer telephones at
Page 59 and 60: 55 The capacity of the hotel PABX i
Page 61 and 62: 57 Fig. 7 The hotel computer, Erics
Page 63: Hardening of Telecommunication Netw
Page 67 and 68: 63 Rise Duration time Time Fig. 7 D
Page 69 and 70: 65 Component Microwave diodes Digit
Page 71 and 72: 67 electrical safety regulations, a
Page 74: ERICSSON ISSN 0014-0171 Telefonakti
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