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Some fragments can be tracked from earth
and a spacecraft can be warned about a possible collision. Once
warned, it can change course and avoid damage. But the problem is
the presence of fragments that are too small to be detected by
radar; these are the ones that damage spacecrafts. Besides, the
resultant fragments from the collision add to the amount of debris
floating around in the earth’s orbit.
Will the debris stay forever?
Well no, an estimated 400 bits of debris do plunge back
downwards to the earth every year. This is unlikely to cause damage
to the earth, as the process of reaching the earth burns them up if
they are small. In the case of big objects like an abandoned space
mission, they can be tracked by radars and the place where they will
fall can be foretold. Until now, such a thing has happened only in
uninhabited areas of the world. In fact, according to experts, at
least one piece of debris falls on earth every day.
How much now?
Estimates say that around 9000 objects that are larger than 10
centimeters are floating around in the orbit. Besides these, smaller
objects that do not show up on the radar may also exist. An estimate
puts the number of particles smaller than one centimeter in size at
more than tens of millions.
Space surveillance networks routinely track
the earth’s orbit for debris. Estimates of extremely small pieces of
debris are made by examining the surface of spacecrafts returning
from space. The collision with small particles would have left
telltale marks on them.
Which portion of the earth’s orbit
contains more debris?
Most of the debris present in the earth’s orbit lies within 2000
kilometers of the earth’s surface. Early space missions and certain
experiments conducted during the cold war period have left a large
amount in space, as the awareness then, about the damages that can
be caused, was very less. Space missions undertaken now are executed
with due care taken to ensure that the debris they generate is kept
to a minimum. Whenever abandoning something in space cannot be
avoided, it is done in the lower altitude region of the earth’s
orbit. This ensures that the debris will fall back onto earth soon.
Debris that is higher in the earth’s orbit
remains for a very long time in the orbit. It has been estimated by
scientists that debris that lies above 1000 kilometers in the orbit
will circle the earth for almost a century. Does it make you wonder
whether these pieces collide with each other? In the last 40 years,
only one such incident has been recorded. |
