[T] he Global Positioning System (GPS) of orbiting satellites on which they rely was originally—and, indeed, remains—a military technology. The system is, for instance, relied upon by the JDAM (joint direct-attack munition) kits that America’s air force attaches to its free-fall bombs to turn them into smart weapons that can be guided with precision to their targets.
But JDAM and similar systems work only when they can receive signals from GPS satellites. And such signals are weak—approximately as powerful as a standard television transmission would be if the transmitter were five times as far away as the Moon is. They are thus easily jammed. For obvious reasons, details of the capabilities of jammers are hard to come by, but a Russian system called Pole-21, for instance, may be able to suppress GPS signals as much as 80km (50 miles) away.
One way to get around this—and to guide weapons automatically to their targets without relying on satellites—is to give weapons a map…. Israel is in the forefront, with a system which it calls Spice. Like JDAM, Spice is an add-on kit that turns unguided bombs into smart ones. It is designed and built by Rafael Advanced Defense Systems, an Israeli weapons company, and comes into service this month.
Spice contains an “electro-optical scene matching system” … [I]ts memory is loaded with pictures of the target area, taken beforehand by aircraft (piloted or unpiloted) or by satellite. …Spice can operate in darkness, and can penetrate smoke and fog. Moreover..Spice stores enough data to cover the entire route to a target.
Spice’s claimed performance is impressive. Rafael says it can guide a bomb released 100km from a target to a strike point within two metres of that target. The firm says, too, that its device is not confused by minor changes in the scenery around a target, which it can find even if some nearby areas have been obscured—say, by camouflage. Spice also has the advantage over GPS-guided weapons of working when a target’s exact position is unknown, or if the co-ordinates have been misreported. All you need is a picture of what is to be hit, and an approximate location, for Spice to find and hit it.
Other countries, in particular America, are following Israel’s lead. In January of this year, America’s air force signed a contract with Scientific Systems, a firm in Woburn, Massachusetts, to develop what that company calls its Image-Based Navigation and Precision Targeting (ImageNav) system….The initial plan is to fit ImageNav to the air force’s Small Diameter Bomb, a free-fall weapon at present guided by GPS. If this is successful, deployment on cruise missiles and drones will follow.
Meanwhile Lockheed Martin, the world’s biggest aerospace firm, is working on an optical-navigation system called Northstar.
Fitting bombs and missiles with vision in this way thus looks like the future. That does not mean GPS will not be used as well—a belt-and-braces approach is often wise in war. But bombs that can see their targets, rather than blindly following their noses to a set of co-ordinates, are always likely to have the edge.
Excerpts Bombs that can recognise their targets are back in fashion, Economist, Dec. 3, 2016