Shooting Satellites

You may have seen stories in the news lately about the U.S. DoD satellite that was falling to Earth and was destroyed by DoD as it neared the atmosphere. Being in the space policy world, I heard quite a bit about this situation. I thought I'd try to write a brief summary of what happened.

The US Satellite, USA-193 was put into orbit, however, operators lost control of the satellite, meaning they had no way to maneuver it. This meant the satellite would have an uncontrolled de-orbit. This is not a particularly unusual occurrence - hundreds of items de-orbit every year. Since 70% of the Earth is water, there is a good probability it wouldn't end up on land. However, USA-193 was large - about the size of a bus, and had frozen hydrazine fuel - which is a hazardous material. According to UN Space Treaties, the United States (as the launching state) would have full liability for any damage caused by the satellite - this would mean helping with clean-up and paying all costs to return things to normal.

Given the slightly unique situation of this large satellite with hazardous material, the US government had to decide whether to engage the satellite or not. (One space policy official mentioned that people had recommended sending the shuttle to rendevous with the satellite and somehow snatch it out of the sky, but he said that since Bruce Willis and Clint Eastwood weren't available, this probably wouldn't work.)

The standard option would be to not engage. This would risk possible (but somewhat unlikely) damage to people or property. There was also a slightly higher than average risk of fatality because exposure to the hydrazine fuel, if the satellite landed on ground, could cause fatalities.

If the satellite was engaged, the fuel tank could be destroyed so that the hydrazine would dissipate in the upper atmosphere and the large satellite would be broken into smaller debris that would be more likely to burn up in the atmosphere or cause less damage hitting the Earth. However, creating more space debris is bad in general, because it endangers other items in space.

And now we're getting to the political aspect of things. To engage the satellite, we would have to alter one of our missile systems for this purpose. Once we use a missile system to engage a satellite, it proves that we have ASAT (anti-satellite) capability. This is an issue, because in January 2007, China tested an ASAT weapon - destroying a decaying Chinese weather satellite. This action was denounced by many of the other world powers. Some (particularly China and Russia) are arguing that the US is only engaging the satellite to make a show of power and respond to China's ASAT test. The US Government denies this allegation.

As you may be aware, the United States did choose to engage the satellite - it was a presidential decision. The satellite was destroyed, including the hydrazine tank. It seems that this issue is now passing, and the operation has gone smoothly.

However, this has once again raised the issue of ASAT weapons and the creation of space debris. Though this fits into that category, it is important to note the distinctions between the Chinese ASAT test in 2007 and the U.S. engagement of USA-193.

In January 2007, China destroyed an aging weather satellite, but did not provide any warning to other countries. In fact, they did not acknowledge that the test had occurred until more than a week afterwards. They still have not provided detailed information on the purpose of the test. The Chinese satellite was in a high orbit, so the thousands of pieces of debris will take hundreds of years to de-orbit. In the meantime, it increases the amount of space debris orbiting the Earth and is a hazard to other satellites and space assets.

The United States, on the other hand, notified other nations of its plans weeks before the final decision to engage the satellite was made. The satellite was destroyed very close to Earth atmosphere, so that all debris should de-orbit within about a week. Also, the technology used to destroy the satellite is being returned to its original purpose. It is also interesting to note that the technology used by the U.S. would not have been capable of destroying a satellite in a high orbit - like the Chinese weather satellite.

This was an interesting issue to see unfold in the media, as ASAT capabilities and space debris are topics often discussed in my space policy classes. Hopefully this was a helpful summary to anyone interested in the basics.