UPDATE: There has been a briefing by the Pentagon which has video of the missile launch, the “kill,” and a brief analysis. The launch occurred on time with no delays due to weather (only 2-3 foot seas). It looks like the shoot down was successful and the hydrazine tank was, in fact, destroyed along with the satellite. The collision occurred at 153 nautical miles above the Earth (~283km).
UPDATEII: Also, what do you know… it looks like there is already amateur photography of the debris field and the hydrazine trail, courtesty of Rob in Maui, Hawaii.

As many of you may know the US military is planning on shooting down a rogue spy satellite in a decaying orbit. It is designated USA-193. The satellite failed immediately after launch and was reported by amateur satellite watchers to have a decaying orbit. The official reason for shooting down the satellite rather than allowing it to deorbit on its own is that the ~5000 pound satellite contains about 1000 pounds of frozen hydrazine propellant that could potentially deorbit into parts of North America. It has been confirmed that the USS Lake Erie, a Ticonderoga class guided missile cruiser, will fire a modified SM-3 missile to intercept the satellite. This may occur sometime within a couple hours of this post, but it looks like weather might delay the shot. Despite assurances from the US, there has been wide speculation that the reason for shooting down the satellite is to test US anti-satellite (ASAT) capabilities, specifically as a reaction to the unannounced test by the Chinese which destroyed a weather satellite dubbed FY-1C in early 2007.

The deployment of military weapons into space has been a matter of concern since the Cold War and the aptly named “Outer Space Treaty” has been ratified by 98 nations. The treaty specifically bans the deployment of weapons of mass destruction into space but does not make prohibitions against ASAT weapons. Both the US and China have tested ASAT technology using the “purposeful miss” method where a missile is fired with the intention of coming within a close distance of a satellite and recording the accuracy. But the last successful satellite “kill” was by the US in 1985 and the Chinese “kill” was after three probable prior attempts. Now the costs and benefits of having ASAT technology and testing it can be debated but the immediate concern is the debris created by such tests. The most significant difference between the planned US shoot down and the previous Chinese one is in the altitude of the satellites destroyed, which has a significant effect on the fate of the debris.

The company that has been tasked with doing simulations of the debris and their paths is Analytical Graphics, Inc. (AGI). They provide an enormous amount of analysis, modeling, and visualization software to the US military and NASA. They also have a lot of great visualizations that are available to the public. Specifically, they have made a bunch of press release and general interest material available about the US intercept of US 193 and the Chinese ASAT test. The biggest difference between the US and Chinese “kills” is going to be the fate of the debris. As this AGI simulation shows (sorry for the .wmv) the debris from the US “kill” will mostly degrade after only a few more orbits and are expected to only last a matter of days. This is because US 193 will be destroyed at ~250km in altitude. FY-1C was destroyed at ~650km which means its debris will not completely deorbit for literally hundreds of years. AGI has also done modeling of the Chinese “kill” and the resulting debris (see the above picture).

There is a cache of publicly available visualizations of the Chinese “kill” made by AGI here. The Chinese ASAT test is the largest orbital debris generating event in history and increased the amount of “trackable items” (larger than golf ball sized) in orbit by 22%. These debris are also going to be very long lasting considering the high altitude of the destroyed satellite. There is a simulation of the debris from this event here. (once again sorry for the .wmv) The difference in the two simulations is immediately obvious.

I would love to know more about the actual ability of people to model these type of events. Apparently we have the ability to detect objects the size of golf balls in orbit. The military is apparently planning on using sea based X-band radar to target and track the satellite and resulting debris. This radar can apparently detect the spin of a baseball from thousands of miles away (impressive eh?). The other really impressive part of this story is the ability of amateur satellite trackers to not only track but give pretty detailed information about classified US government (and I assume other nations as well) assets.