Word: radar
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...Safeguard system has four key elements. PAR (perimeter acquisition radar) detects an enemy ICBM at long range some time after it has been launched, calculates its path, and then passes the missile track along to the less powerful but much more complex MSR (missile site radar). MSR then directs two types of ABMs against the incoming warheads. The long-range Spartan is designed to make an intercept above the atmosphere, at altitudes between 200 and 400 mi. The smaller Sprint would seek out and destroy warheads that penetrated the Spartan screen by intercepting them within 40 miles of the target...
...question about how well the U.S. ABM would work-or if it would work at all-turns on the vulnerability of its radar guidance. Without it, Spartan and Sprint would journey blind. A nuclear blast outside the atmosphere can create radar blackouts lasting critical tens of seconds, as both U.S. and Soviet tests demonstrated in the early 1960s. A "precursor warhead," launched just ahead of a missile attack and detonated as a kind of nuclear smoke screen for the following ICBMs, could black out U.S. perimeter acquisition radar and disrupt the ABM defense...
Cornell Physicist Hans Bethe, a Nobel laureate who believes Safeguard to be sound in principle but not yet necessary to U.S. defense, replies that it is possible to intercept the enemy warheads with Sprints at altitudes below 30 miles, where radar blackout is not a serious problem. Further, the PAR installations are designed to overlap enough for one to take over the functions of another -at least in theory-if the second is blacked out or even physically destroyed by a missile that penetrates the ABM defenses...
...tested under conditions accurately simulating a nuclear attack. Wiesner also contends that any ABM is limited by the defender's guessing about the technology of the weapons it is designed to intercept. The attacker can add chaff and decoys as "penetration aids" to confuse the defender's radar and exhaust the supply of ABMs. Says Wiesner: "I do not think the defender is ever going to know really what to expect; the variety of techniques available to a nation planning an offensive system is great enough to keep an anti-ballistic-missile system totally off balance...
...anticipated. Most food flights flown by civilian crews have been grounded until flight rules can be worked out that are agreeable to both combatants. Planes that do make the flight are targets for the newly unleashed MIGs or for antiaircraft fire that appears to be directed by five radar-equipped Russian trawlers lying off the coast. Flying into Uli aboard one such flight last week, TIME Correspondent James Wilde found Biafrans grim. The struggling country had a good harvest recently, but supplies will last no longer than three months. Food rationing has already begun...