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How Israel's 'Iron Dome' intercepts incoming rockets in Gaza conflict

Iron Dome
An Iron Dome launcher fires an interceptor rocket in the southern city of Ashdod, Israel on Nov. 16, 2012.Amir Cohen / Reuters

As the conflict between Israelis and Palestinians continues along the Gaza border, Israelis have been putting to use an anti-rocket defense system called "Iron Dome" meant to intercept Palestinian rockets that are headed for major population centers. Along with its tally of "terror target" strikes, the Israel Defense Forces' Twitter feed has announced the number of incoming rockets grounded by the system.

Iron Dome is actually a nickname for the "Dual-Mission Counter Rocket, Artillery and Mortar and Very Short Range Air Defense System," a missile battery that works with sensors to detect and intercept short- to medium-range threats like rockets. It was commissioned by Israel in 2007 following a year in which the country endured thousands of missile attacks, mainly concentrated in the country's northern region.

Iron Dome infographic
Iron Dome infographic from a Rafael Advanced Defense Systems promotional brochure.Rafael Advanced Defense Systems Ltd.

Built by Rafael Advanced Defense Systems, the full  system is made up of three parts, all of which are relatively portable. 

A radar unit watches for threats in a radius up to about 40 miles. 

Information on spotted projectiles is passed to a Battle Management and Control truck, where the information is evaluated and the command is given to either intercept or ignore. The projectile data is then passed to the interceptor unit, which launches a missile programmed to cross paths with the incoming rocket or shell, and detonate it in a way that is as harmless as possible. 

This week, Iron Dome has been up against the rockets fired by the Qassam Brigades, the military faction of Hamas, the Islamist political party and militant group that has been governing the Gaza Strip separately from the West Bank-based Palestinian Authority since 2007.

The rockets are crude, technologically speaking: Little more than an explosive charge attached to the end of a tube of propellant. While this means the rockets can be manufactured and deployed in great numbers, it also means that they have a relatively slow, ballistic trajectory that is an easy target for a fast-moving, guided missile.

Each missile fired from an Iron Dome unit costs around $40,000, but the cost appears to be offset by effectiveness. The Israel Defense Force has previously stated that as high as 85 percent of the enemy rockets can be intercepted — although its effectiveness was tested under significantly less intense bombardments. As of Friday evening, current estimates. based on IDF reports. place rockets fired into Israeli territory at just over 600, with nearly 250 reported to be shot down by Iron Dome missiles.

Iron Dome blasts apart a rocket fired from the Gaza Strip by Hamas as it approaches Sderot, southern Israel, 15 November 2012.Jim Hollander / EPA

That may sound like a far cry from 85 percent accuracy, but the Iron Dome batteries simply ignore projectiles that are predicted to land in unpopulated areas like farmland or water. So while hundreds of rockets have been allowed to strike Israeli soil, comparatively few of them are causing serious damage or casualties.

The U.S. partly bankrolled the development of Iron Dome, beginning with $200 million requested by President Obama in 2010 and later approved by Congress. As much or more is currently being considered for inclusion with other defense spending, though it may be contingent on Israel consenting to a technology-sharing agreement. The Iron Dome was first deployed in March 2011, and it intercepted its first enemy rocket that April.  

Devin Coldewey is a contributing writer for NBC News Digital. His personal website is coldewey.cc.