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Science Frontiers ONLINE No. 25: Jan-Feb 1983 |
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Lageos Falls Too Fast
In May of 1976, NASA launched a geodetic satellite into an orbit over the poles about 3700 miles out. The satellite, called Lageos, is covered with laser reflectors so that it can be tracked with high precision. At its altitude of 3700 miles, the earth's atmosphere is supposed to be so thin that friction will bring the satellite only 1/250th of an inch closer to the earth each day. The trouble is that Lageos actually falls at ten times this rate. In 1979 it descended 60% faster than it does now. Lageos will stay in orbit several hundred thou-sand years, but space scientists are understandably concerned about their theories about the upper atmosphere. Many suggestions have been made to explain this anomaly. Some say the atmosphere is thicker than expected; others prefer to think there is more helium than predicted; but the "plasma drag" effect seems to fit the situation the best. Lageos may, in fact, be electrically charged and interacting with the surrounding cloud of electrically charged particles and is ever so slightly braked by the electrical forces.
(Maran, Stephen P.; "Fall from Space," Natural History, 91:74, December 1982.)