April 2, 2007:
Last week, an airliner thought it
almost got hit by pieces of a Russian satellite, while approaching New Zealand. A Chilean Airbus 340 was
approaching Auckland airport, when it spotted several flaming objects a few
kilometers away. At first, it was thought to be space satellite debris. The
Russians had warned New Zealand that one of its satellites would "de-orbit"
nearby. At first it was believed that the Russians miscalculated the exact
location, and arrival time. Then the Russians pointed out that space satellite
debris would have not been visible, since it would have burned up before
reaching the altitude (about 35,000 feet) the airliner was at. The fiery items
the crew and passengers saw were clearly headed for planetfall.
Most satellites have enough mobility to allow ground
controllers to order the satellite to move lower and burn up in the atmosphere
(to "de-orbit"), when the bird is worn out and no longer of use. This
is usually done over some isolated portion of the globe, like the South
Pacific, where there is little air or ship traffic. However, you have to do
your calculations carefully, so that the descending satellite does not arrive
at the wrong place, at the wrong time. Dozens of satellites, or parts of
launchers, are de-orbited each year. The owning nation is supposed to warn
mariners and airlines, operating in the area, as far ahead of time as possible.
Meteorites are also tracked, but not as carefully as orbital items. Many more
untracked meteorites enter the atmosphere each year, than do satellite debris.