March 22,2008: The U.S. Army has ordered another $130 million worth of the AN/PAS-13 thermal sights. This device enables infantry to see through darkness, mist and dust storms, because it can make out differences in heat.

The AN/PAS-13 actually comes in three sizes, to accommodate the different ranges of infantry weapons. The smallest one, weighing 1.8 pounds, is used on your basic M-16 or M-4 assault rifle. This sight has a range of 550 meters. I uses 4 AA batteries (lithium, as used in cameras), which gets you about 5.5 hours of use.

The next version weighs 2.8 pounds, has a range of 1,100 meters and is used in 5.56mm and 7.62mm machine-guns. This sight requires six AA batteries (for 6.5 hours). The heaviest version weighs 3.9 pounds, has a range of 2,200 meters, and is used by heavy machine-guns and snipers. This one also requires six AA batteries (for 6.5 hours).

The AN/PAS-13 began showing up in Iraq and Afghanistan about a year ago, and now everyone wants one. About 20,000 have been delivered so far, and production is headed for 3,000 sights a month. Unless there is a much improved new version in the next few years (no one is sure, engineers can be unpredictable), the army plans to buy as many as 150,000 AN/PAS-13 sights (at a cost of over $10,000 each).