AP Photo

Sometime on Friday, a 6.5-ton satellite the length of a small bus will plunge back to Earth. Deployed from the space shuttle Discovery in September 1991 and decommissioned in December 2005, the Upper Atmosphere Research Satellite (artist's concept in image) measured chemical compounds found in the ozone layer, wind and temperature in the stratosphere, and energy streaming from the sun. According to NASA analyses, as many as 26 components weighing a total of 532 kilograms could survive reentry and strike Earth at scattered sites from 500 kilometers to nearly 1300 kilometers ...