July 18, 2006

About that Hezbollah cruise missile

A correspondent who regrettably no longer blogs pointed me to the dialogue here which refers to the possibility of Lebanon Armed Forces radars being used to direct the attack on the INS Hanit missile boat by a Hezbollah cruise missile on the weekend. A couple off-the-cuff observations.

The C802 missile, built by China and sold to Iran (and used to take out an American-built missile ship in Israeli service, since we're at it), which Israel says was used in the attack on the Hanit, is believed to use the same method of most anti-ship missiles, combining inertial guidance, and active radar homing* onto a target. In lay-speak, that means the missile initially flies to a given set of co-ordinates, then turns on its own terminal radar guidance, acquires its target for itself, and flies into it. This is standard in anti-shipping missiles because of their very long range, which tends to limit their ability to home in on a radar signal from another source, such as a launching ship. Ship radar systems supporting these missiles are generally only used to detect targets to plot the intercept courses for the missiles, but the missile is not wholly dependent on those radars to function. This is the method used to fire the Exocet and Harpoon missiles, as well as the C802.

What this means is that, in theory, one can just fire such a missile at just about any set of coordinates, and, if it finds anything in its path after it arrives there and turns on on its radar beam, it will likely attack it, without the firer ever knowing what the target was.

The ocean's a pretty big place of course, so that would normally be a waste of a missile. Generally you want to fire the missile at a place where it is highly probable it can acquire something you want to kill, which for long distance kills means you need radar or sonar or some other indication that a target is present at that spot.

For short range, close-to-shore kills, that may not even be necessary. The IDF boat was said to be 10 nautical miles off shore, at the edge of visual detection. In theory, Hezbollah could have fired the missile in question on an intercept course at that range without using shore-based radar at all. Evidence that a second missile fired at the same time that hit a tanker nearby would tend to support that, either because it was the result of an incorrect visual ID, or it was sent to slightly different coordinates, missing the intended target and hitting the next ship in its path (which these missiles tend to do). But there is no evidence so far that a shore radar was required to execute this attack (and good evidence that there wasn't... it's highly unlikely the IDF ship would have cruised with its anti-missile systems off if it knew it was actively acquired by an active shore radar system, which its own electronic countermeasure systems would have been able to detect.)

A very similar attack (a missile launched off a trailer on shore probably on the basis of a visual ID) wrecked the HMS Glamorgan in the Falklands War in 1982. The Glamorgan was also about the same distance offshore as the Hanit when the trailer-based Argentinian Navy Exocet was fired in its general direction, killing 13 British sailors upon impact.

*typo corrected, thanks to correspondent John D.

Posted by BruceR at 01:07 PM