Word: orbit
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...Challenger's crew learned that a dust storm had developed across the Atlantic at an emergency landing facility near Dakar, the capital of Senegal. Under NASA's tight safety rules, a shuttle cannot go up unless it has a place to land if something goes wrong before it reaches orbit. Such facilities have never been needed, but every risk had to be minimized. Challenger's crew would have to wait another 24 hours...
...problem, as outlined in a classified report from the Defense Intelligence Agency, is the possible development of a new Soviet weapon--the "fast-burn" rocket. According to the report, such a device could speed into orbit and shut down its engines before the heat-seeking sensors of SDI satellites could home in on its jetstream. The report predicts that the Soviets could "develop, produce and deploy" fast-burning rockets as early...
...next two centuries of cometary science were relatively uneventful. In 1823 German Astronomer Johann Franz Encke, who calculated the orbit of a periodic comet that bears his name (it reappears every 3.3 years), insisted that the orbit of "his" comet could not be explained solely by gravity. He proposed that "ether," an invisible theoretical substance that at the time was believed to pervade space, exerted drag on the nucleus, slowing it down. After observing flares streaming from Comet Halley's surface in 1836, another German astronomer, Friedrich Wilhelm Bessel, conceived a more plausible concept, the fountain theory. Bessel proposed that...
...time the most powerful telescopes first catch a glimpse of a comet, the coma already obscures the nucleus beneath. For every revolution a typical comet makes around the sun, its diameter is estimated to shrink about 6 ft. Hence the original size of the comet, the length of its orbit and how close it gets to the sun will determine its life-span. Astronomers estimate that Halley's, which has a relatively short period, will probably last another 225,000 years, a mere wink of astronomical time...
...most important contributions from the Vega program will be what is called the Pathfinder concept. Together the probes will attempt to reckon the position and orbit of Halley's nucleus with a precision impossible from ground-based observations and then beam the data back to the Soviet Union, which will in turn relay the information to European mission control in Darmstadt, West Germany, in time for Giotto's rendezvous on March 13. Precision is of the essence: zeroing in on a nucleus that scientists estimate measures only two to six miles in diameter and is traveling some 154,000 m.p.h...