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by staff writers
Bethesda MD (SPX) Jun 21, 2012
Last week there was an event that tells us the "end" is nearing; the end of BIG SPACE. Ever since the first satellite was launched some 55 years ago, the space community has thought of space as being big, so big that there was almost no chance that two objects in orbit would ever collide.
In fact, this myth held true for the first 50 years. But in the last five years people have begun to doubt the vastness of space.
There was the Chinese ASAT test about five years ago when an interceptor hit an expired Chinese weather satellite. This event by itself is not a big deal. However, the explosion occurred at about 865 km altitude, right in the zone of the highest satellite and debris population.
The result was a significant increase in space debris in near-earth orbits. About two years later, the expired Kosmos 2251 collided with the operating Iridium 33.
The two spacecraft met at an altitude of 789 km with a relative speed of 11.7 km/sec. The resulting two debris fields effectively added hundreds of additional debris objects to the already densest zone of near-earth space.
The total number of dangerous debris objects in the 700 - 1100 km altitude range is estimated to be in the hundreds of thousands, if not in the millions. Of course, there is debris all over space.
For example, the International Space Station (ISS) resides at about 400 km. As debris decays from higher altitudes, each piece invariably passes through the ISS's altitude. Thus, we can expect that the station is going to experience at least occasional hits from debris. Near misses of large objects are recorded almost every week. Last week there was a small hit.
Window 2 on the ISS's Cupola module was hit by a minor debris object. Fortunately, the window's protective shutter was closed at the time.
The Cupola has provided ISS crewmembers a stunning view of our planet and allows the viewing of arriving vehicles. Nevertheless, this incident does remind us of the ever increasing threat from debris hits. Ultimately, the debris population in the high-density band will overwhelm all satellites in the region, rendering that zone a denied region of space.
No one will be able to fly a satellite safely between 700 km and 1100 km. This is not an "if", but a "when" situation. The denial process has already begun and will one day accelerate in an exponential manner toward the end.
The question is: "What are we to do about it?"
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