The IDF has set up a joint command center at the base in the Negev that is home to the American X-Band radar, deployed in Israel last October to bolster defenses in the face of Iranian threats. When the radar was first set up, Israel was told that it would not be allowed to maintain a presence at the base. Several months ago, the Americans changed their position and allowed an Air Force major from the Air Defense Division to maintain a permanent presence at a joint command center inside the base. The base is operated by some 100 American soldiers from the European Command. The X-Band radar participated in the successful test of the Arrow anti-missile weapon last month. Defense officials said the radar played an important role in Israel's defense architecture because, while incapable of directing the Arrow toward its target, it could successfully track a so-called "split warhead," which employs decoys. Once a warhead of this type comes apart, officials said, several targets appear on the radar screens of Arrow controllers, who then must work to identify the actual warhead. The X-Band radar, they explained, can readily do this and then transmit relevant data to the Arrow command center at Palmahim or Ein Shemer. "We are preparing for future threats that will fly at higher altitudes and have split warheads," one official said. Iran is believed to be developing a split-warhead capability for its long-range Shihab missile arsenal.