Japan is upgrading its 24 Patriot missile batteries and will have it completed by the end of the decade. The main improvement is to increase the range of the PAC-3 anti-missile missile to 30 kilometers. The upgrades will be performed in Japan under license from the American manufacturer.
Japan began expanding, redeploying and upgrading its Patriot forces in 2007, in response to the growing threat posed by North Korean ballistic missiles and nukes. This was trial and error at first. For example Japan had to move one of its Patriot anti-missile launching sites because a 38 story building going up nearby threatened to become an obstacle if any missiles were fired. Initially Patriot anti-missile missile batteries were set up inside Tokyo. This had to be done because the anti-missile version of Patriot (the PAC 3) can only defend out to about twenty kilometers. These launching sites were considered "emergency launching sites." The Patriot system is mobile and built to be moved quickly and set up in new locations.
Normally, Patriot, or any other type of anti-aircraft missile is positioned in a wide open space, to avoid missiles colliding with anything but their intended targets. Missiles are not really guided at take-off, just pointed in the general direction of the target. The guidance system kicks in within a few seconds, but by then the missile may have gone several kilometers. That's because the solid fuel rocket motor is basically a slow burning explosive. The fuel is often all gone very quickly.
Patriot missiles are also very noisy when they launch. Basically it's a sudden, and very loud, explosion. If you are at home asleep when that happens, you will definitely wake up. This was the experience of civilians living within several kilometers of Patriot batteries in northern Saudi Arabia in 1991. The Japanese can live with the loud noise of a Patriot missile taking off, but not with the after-effects of said missile colliding with a nearby skyscraper. The Japanese solved the tall buildings problem by moving some batteries to high ground, usually in a park.
Each Patriot battery is manned by about a hundred troops, and each contains a radar and four launchers. A battery can fire two types of Patriot missile. The $3.3 million PAC 3 missile is smaller than the anti-aircraft version (PAC 2), thus a Patriot launcher can hold sixteen PAC 3 missiles, versus four PAC 2s. A PAC 2 missile weighs about a ton, a PAC 3 weighs about a third of that. The PAC 3 has a shorter range (about 20 kilometers) versus 160 kilometers for the PAC 2 anti-aircraft version used against low flying UAVs. Patriot can also take down cruise missiles or larger UAVs.