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Artist rendering of gravity tractor - image courtesy of B612 Foundation
DailyTech's International Space Updates for January 2007

Some experts seem to agree that it is only a matter of time before an asteroid or meteor strikes Earth in the future. While millions of them are aimlessly floating around in space, 200,000 to 400,000 of them come within range Earth, according to reports. That is why NASA astronaut Edward Lu wants NASA to deploy a spacecraft which would be able to divert asteroids so they will not run into the planet. In theory, the craft's gravitational pull would change the asteroid's orbit. UK researchers are planning on using a superior telescope located in Hawaii to help locate Earth-threatening asteroids.

India has successfully recovered the Space capsule Recovery Experiment (SRE-1), a capsule that has been orbiting around the Earth at an altitude of 637km. The SRE-1 floated in space for 11 days before splashing into the Bay of Bengal earlier in the week. The Indian space agency used the SRE-1 to test its ability to accurately track and recover a space capsule landing back on Earth. The head of the team that created the capsule said that “the mission is a great success.”

Chinese space officials still continue to claim that its anti-satellite test is not a hostile act. The Chinese government confirmed that on Jan. 11 it launched a missile aimed at destroying an aging weather satellite, and the test has the United States and Japan worried. While the Chinese previously discussed its plans with U.S. Officials, both the Japanese and U.S. Governments want clarification on the future intentions of the Chinese.  With some form of a space war on the minds of many government officials, this recent incident only has more people worried.



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Mine field
By Shadowself on 1/25/2007 12:19:31 PM , Rating: 2
"With some form of a space war on the minds of many government officials, this recent incident only has more people worried."

This is not the bottom line issue at all. The issue is debris.

Yes, there is a significant amount of debris already up there, but most of it is below about 600km. There were a very limited number of fragments at the approximately 800km orbit of the Chinese satellite China "shot down". Virtually all those pieces are too small to destroy a satellite and cause more debris.

In reality it was not "shot down". It was hit and broken up by the weapon. Now there is a cloud of debris orbiting at 800km. This cloud is slowly dispersing. It is kilometers in diameter now and will be several 10s of kilometers in diameter long before the first piece comes back and burns up which will take decades, not years. Some of the objects in the cloud are very significant in size and mass. The debris field has effectively created a mine field at 800km. Remember, this was a polar orbiter. Its path took it (an now the debris field's path takes is) over the entire Earch creating a "shell" at approximately 800km.

Many satellites use the 800km orbit and peacefully coexist by maneuvers which keep them from hitting each other. Little maneuvers are used because moving as little as 20-50 meters is plenty to miss another satellite and 20-50 meters is almost nothing in propellant used. Now these satellites will have to move 10s of kilometers and use much more propellant to be certain to avoid crossing paths with this cloud.

And what if they don't completely avoid the mine field? What if at 780km a satellite gets hit with a piece and it gets destroyed and creates more debris? It just compounds the problem.

What satellites use 800km (approximately)? Oh, just the NOAA birds, the DMSP birds, the future NPOESS birds, commercial sats such as Orbcomm, etc. Now all of them will have to dance around this mine field for several decades to come.




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