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Successful Military Satellite Destruction:
Two U.S. Experts Publish Important Details
David Wright, senior scientist at the Global Security Program and James A. Lewis, Center for Strategic and International Studies delivered background information about the reasons for the U.S. military to particularly target the Hydrazine tank: It is "tough enough to survice catastrophic reentry into the atmosphere. Other space vehicles typically carry not more than just a few pounds, and the reentry point can be planned with reasonable accuracy. In this case, the tank was full, and no one knew what could happen. The risk was, that the equivalent of a 1000 pound bomb could have exploded in a populated area on earth, causing death and destruction."
Comment by David Wright, Sr. Scientist, Global Security Program, UCS
Missile defense and ASATs:
I am frequently asked what the intercept of satellite US193 indicates about the effectiveness of the Aegis system against an actual missile strike. The answer is "very little", since intercepting a satellite is very different in important ways from intercepting a missile warhead. The biggest difference is that the satellite was not accompanied by decoys or other countermeasures, which would be the case for a missile warhead in a real-world attack. Decoys keep the interceptor from identifying which object to home on. Moreover, in a real-world missile attack, the defense will not know in advance the timing and trajectory of the target, which it did know in advance of intercepting the satellite.
A second question is whether there is a downside to demonstrating that U.S. missile defense systems have the ability to destroy satellites. Unfortunately, yes. The intercept will make it much more difficult to convince other countries that they should not develop a similar anti-satellite capability.
Satellites are vulnerable to attack and disruption because they can be seen and easily tracked in space. Because the United States is reliant on satellites for a wide range of purposes, it would greatly benefit by working to prevent the deployment and use of ASATs by all countries.
The testing or use of weapons that destroy satellites can also create large amounts of orbital debris, which can stay in orbit for decades or even centuries. This debris can threaten satellites in orbit and can ultimately hinder the use of space for all countries.
The satellite shoot down will also complicate relations with Russian and China. They have been pushing for international negotiations on banning anti-satellite weapons, which the United States has resisted. These countries will regard U.S. missile defense systems as de facto ASAT systems. If the number of U.S. missile defense interceptors grows, so will the apparent U.S. offensive ASAT capability.
Comment by James A. Lewis, Center for Strategic and International Studies
Satellite Shootdown Comments - Feb 20, 2008
People are looking for ulterior motives for the shootdown because the official explanation – preventing 1000 pounds of hydrazine falling from the sky. Hydrazine is highly dangerous stuff. It's unstable, corrosive and explodes easily. That means that the fuel tanks for hydrazine are made extra tough. Unfortunately, the strength that lets the fuel tank carry hydrazine safely into space also means that the tank is tough enough to survive catastrophic reentry. When the shuttle broke apart on reentry a few years ago, the hydrazine tank was one of the few items to survive the fall unscathed. In that case, however, the tank contained only a few pounds of hydrazine. In this case, the tank is full. The risk is that the equivalent of a 1000-pound bomb could end up crashing down into a populated area.
Lots of debris falls from space every year – the boosters that carry satellite up come down pretty quickly. Elderly satellites are deorbited without much notice. The difference is that these are usually controlled reentries, where the impact point is planned (usually in water) and there is a degree of control as to the timing. This is an uncontrolled reentry. It's possible to predict where impact will occur with some accuracy, but a number of factors can through the prediction off. Presumably, the U.S. predicts it will fall near or close to a populated area. Usually these things fall into water – it covers ¾ of the planet's surface – or an unpopulated area. I know of only one reported case where someone was hit by a piece of a falling satellite, when a 20 pound chunk of aluminum from a Chinese CBERS satellite hit a boy in Shaanxi province – the press reported that he suffered a "fractured toe."
The hydrazine explanation seems far-fetched, but the alternative explanations make even less sense. The U.S. doesn't need to do this to impress the Chinese. They were already impressed by earlier successful tests, including the last one where an SM-3 missile launched from an Aegis cruiser hit a warhead 87 miles above the Pacific Ocean. This didn't get a lot of public attention, but the Chinese military was sure to have followed it closely, if only because the U.S. has a cooperative missile defense program using Aegis with Japan, which the Chinese think could be used to defend Taiwan.
This test and China's ASAT test really aren't comparable. This is a ballistic missile defense test rather than an anti-satellite test. An anti-satellite test would have attacked the target while it was in orbit. A BMD test attacks when the target is in reentry. Hitting the target at a lower altitude reduces the risk of debris. One of the problems with the China ASAT test (aside from not telling anyone in advance) is that it left a large debris cloud orbiting the earth. The debris from this Aegis test will be at a lower altitude and be more quickly drawn into the earth's atmosphere, where they will burn up.
Success is likely in this effort, but not assured. Of the ten Aegis tests, eight resulted in hits. There is also the possibility that the satellite will behave erratically as it hits the atmosphere, making it a more difficult target. Variants of the SM-3 missile can be used against aircraft or ships, but these variants carry explosive warheads with proximity fuses (meaning the warhead only as to get near the target, not actually hit it). The missile defense variant uses a 'kinetic' warhead, basically a large lump of metal that crashed into the target. It will be moderately embarrassing if it misses.
The notion that secret high tech gizmos would fall into the wrong hands has some merit, but not enough to justify a shoot-down. There are always pieces of wreckage when a satellite falls to the ground. When they fall in the Canadian Arctic, the U.S. and Canada collect the pieces. When a nuclear powered satellite built by the Soviet Union crashed in Canada in the 1970s, the Soviets said they didn't want the pieces back. When a Chinese rocket carrying a Western-owned communications satellite blew up shortly after launch, the Chinese carefully collected all the pieces and tried to examine them before turning them back, but the most sensitive items were charred and cracked beyond recognition. The probability of gaining useful information from the crash is low, as the best technology would have to survive reentry and the debris would have to fall in an opponent-controlled area. The probability of surviving reentry and landing in a hostile controlled area are too low to explain the decision to shoot down.
The one scenario that doesn't get as much attention is planetary defence, possibly because it sounds silly. The notion that the U.S. should add intercepting meteorites or asteroids before they strike the earth to its defense missions seems pretty far-fetched. These events are so rare as to be improbable. On the other hand, supporters say, an asteroid strike wiped out the dinosaurs, drastically changed the environment, created a year-long winter and so on. It still sounds far-fetched. On the other hand, a 200-foot wide meteorite that struck Tunguska Siberia in 1908 had the effect of a nuclear explosion (without the radiation aftereffects). If there was warning that a similar event was about to occur over a populated area, it would be nice to have the ability to stop it. It's not worth spending much time worrying about being hit by asteroids, however, or even by satellites, but having spent all that money on missile defense, it's nice that it finally has some practical use.
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