Israeli weapons developers traced the paths of hundreds of rockets fired by militants during the recent Gaza fighting, hoping the data will help perfect a planned interception system, defense officials said Monday.

Rockets fired by militant groups like Hamas and Hezbollah are among the most potent threats facing Israel, with the majority of the country's population now in range from either Gaza or Lebanon. Southern Israel has faced rocket fire from Gaza since 2001, while to the north, thousands of rockets from Lebanon were fired during Israel's war against Hezbollah guerrillas in 2006.

During the Gaza offensive, which ended on Jan. 18, Israeli teams collected data on how the homemade rockets and the military-grade Katyushas fired by Gaza militants behaved in different weather conditions and how they were picked up by the interception system's radar, which is already operational, the officials said.

The data will be used to assist in the construction of the so-called "Iron Dome" system, the officials said.

They spoke on condition of anonymity because the system's details remain classified. The Iron Dome, which is supposed to protect Israeli towns from rocket fire, is set to be operational in 2010.

The system is being designed as an answer to the Gaza rocket fire, which so far has eluded Israel's sophisticated military.

Iron Dome has been criticized by some experts because of its cost — each interceptor will cost between $30,000 and $40,000 — and because it needs 15 seconds to respond, too long to stop rockets from hitting targets adjacent to Gaza.

Iron Dome's first intercept test is slated for the end of 2009.