…well disrupted at least.

The US Department of Defense today released a statement describing how the US Navy Triconderoga class Aegis Guided Missile Cruiser USS Lake Erie (CG-70) fired a single, modified RIM-161 Standard Missile 3 (SM-3) from the Pacific ocean and hit the errant spy-satellite which, they say, was travelling at “over 17,000mph”. Arleigh-Burke class Aegis Guided Missile Destroyers USS Decatur (DDG-73) and USS Russell (DDG-59) also took part in the operation as backups for USS Lake Erie.

It is reported that in another Pentagon statement, the speed of USA-193 was 22,783mph when shot at about 133 miles altitude (71 miles into ’space’ which officially begins at 62 miles in altitude). The DoD statement says that the debris from the satellite will mostly burn up within 24-48 hours and the rest within 40 days. However, a Professor Richard Crowther, a ’space debris expert’ with the STFC, was quoted in a BBC article stating that in his opinion, up to 25% of the satellite’s mass could still survive re-entry.

“USA-193″ as it is called by amateur satellite trackers or NROL-21 by it’s launch number, was believed to be a radar reconnaissance satellite launched in December 2006 but which failed to deploy into proper operation. The orbit of the satellite had been decaying ever since and the US government stated their reason for ‘destroying’ the satellite was to protect humans from the risks of the satellite’s near half-ton of hydrazine fuel stored on board. Unfortunately, US officials no cannot say whether the fuel tank was properly destroyed by the AEGIS missile and, as such, there could now be 450kg of hydrazine ice flying around the planet pending re-entry. If you happen to see a spacecraft fuel-tank lying around some time soon, don’t go near it.

Of course, Russia and China have immediately accused the USA of ASAT willy-waving. The fact that the interception and destruction occurred outside the atmosphere means that at least part of the Outerspace Treaty on weapon use in space has been violated. China is calling for more information about the operation as (presumably) they believe this to have been a deliberate ASAT technology test and it doesn’t help the USA’s position much that they decried China’s recent ASAT test. Russia is just out-and-out calling this an ABM test and you can see their point. If Aegis can hit an object flying at 17,000mph + at 133 miles, it can probably hit slower, lower ICBMs. Aegis is after all, by design, an Anti Ballistic-Missile defence system.

Ultimately, all is fair in international love and cold war

Update: Fixed km/miles mistake.

Update 16:49: I’ve just watched the intercept video and the press officer states that the intercept occurred at 153 nautical miles altitude. This is equivalent to the 133 ‘international’ standard miles that I mention.

The US pentagon has announced that the failed reconnaissance satellite speculated around the web to be USA-193/NROL-21 is to be shot down to prevent a possible atmospheric discharge of nearly half a ton of hydrazine monopropellant contained on board.

The ’spy’ satellite, speculatively identified by satellite tracking enthusiasts across the world as USA-193 apparently failed to deploy correctly when it was launched back in December 2006. It would have been in a gradually decaying, uncontrolled orbit thereafter.

US officials say that they will use a RIM-131 Standard Missile 3 (SM-3) to destroy USA-193 before it enters the atmosphere so that the hydrazine propellant will be dispersed safely in space. The SM-3 is a fairly hefty 4-stage missile and part of the Aegis Anti Ballistic Missile System. The missile will be fired from an Aegis cruiser or destroyer. US President George Bush has given approval for one missile to be fired but a further two Aegis ships will be standing-by downrange. In case of a miss by the first ship, a decision will be made on whether or not to fire again from one of the other ships.

General James Cartwright, the Vice Chairman of the Joint Chiefs of Staff stated that the optimum time frame for the destruction of the satellite would be in a window opening for about one week beginning in four days time. If successful, the satellite would be reduced to small components of debris which would largely burn up on re-entry.

I haven’t been able to find out yet what altitude the satellite will be traveling at yet (perhaps the orbit tracking buffs will come up with it) but with the DoD already playing down any similarities with China’s recent destruction of a satellite with an ASAT missile, it’s possible that it may be over the 100km mark and that could mean a curfuffle with Russia, China and the UN over the outerspace treaty which bans the use of weapons in space.

In the mean time, mind your heads

According to press reports, a US reconnaissance satellite is expected to make an uncontrolled reentry after communication and control with the satellite was lost.

The uncontrolled nature of the reentry means that while the satellite is expected to reenter the atmosphere in the next month or so, it can’t be said for sure where the remains of the satellite will land. A large enough chunk of satellite landing in a populated area could cause damage to property or even injuries or fatalities. The greatest probability, however, is that it will hit an ocean area but this may still present a hazard to shipping or aircraft.

Knowing what sort of satellite chunks to expect is really about knowing the construction of the satellite itself. Unfortunately, the satellite in question is highly classified so the best we can do is speculate.

There’s  at least a couple of types of spy satellite up there, radar survey and optical. The US optical reconnaissance are often said to resemble the hubble space telescope (pointing down not up!). Referred to as ‘Keyhole’ or ‘Misty’ by the general public, this series of optical satellites is said to carry a mirror 2-3 meters in diameter which would probably be somewhat heavy and thick and I would guess liable to survive reentry.

Then there’s the radar satellites which I can’t think of having any single massive component although in the interests of ’stealth’ (if such a thing is possible for satellites) they may forgo highly-observable solar arrays and instead use RTGs. An RTG may release some radioactive fuel upon reentry but it would likely be released over such a wide area that it would be barely detectable above background. In the 1970s, an RTG on the Apollo 13 LEM survived reentry from lunar-return velocities and the subsequent impact without releasing any radioactive material. The biggest risk to your health from a Satellite RTG it would seem, would be if it hit you on the head.

Having looked around the web at this story, there is some discussion among amateur satellite tracking enthusiasts that this may be NROL-21 / USA 193, a satellite launched in December 2006 which failed to deploy correctly. Due to the low orbit, it is speculated that this is a radar reconnaissance rather than an optical satellite.

Gordon Johndroe, a spokesman for the National Security Council declined to comment as to whether the satellite may be ’shot down’. The USA has successfully tested ASAT weapons in the past but could be very hesitant to use them for a few reasons I can think of:

• It may contravene the Outer Space Treaty
• The debris from a ‘kill’ would spread out and become harder to track while also presenting a hazard to other satellites / spacecraft.
• The net result of a ‘kill’ would be that you still had the same amount of mass going in roughly the same direction at the same speed but it would all be coming down in different places (depending on the drag coefficient of each fragment)

I’ll be interested to see whether we get any more news on this reentry. It really could be the case here that ‘no news is good news’