Explanation:
How often do satellites collide?
Although minuscule space debris may strike any satellite on occasion, the first known
collision between time two full satellites
occurred only last week.
Even though thousands of
satellites have been launched, the low collision rate is caused by the great vastness of space.
Last week, however, a defunct Russian communications satellite named
Cosmos 2251 smashed right into an operational US communications satellite named
Iridium 33 over
Siberia,
Russia.
Both satellites were destroyed.
The sheer number of massive particles in a
dispersing debris cloud, depicted in an inset
image above, increases the risk that other operating satellites might be struck by a harmful fast-moving projectile.
The collision occurred in
low Earth orbit only 750 kilometers up, a height shared by many
satellites but significantly higher than the 350-km high human-occupied
International Space Station.
Since satellites may disintegrate when struck by fast-moving
space junk, the crash focuses concern that a future
dramatic satellite collision may one day start an
ablation cascade
of increasingly more collisions.
The result
could then render future human space flights increasingly risky and expensive satellite lifetimes increasingly short.
digg_url = 'http://apod.nasa.gov/apod/ap090218.html'; digg_skin = 'compact';
