The Science Behind Israeli Sirens

Warning sirens have sounded over 4,000 times in Israel over 45 days of fighting with the Gaza Strip. When do sirens sound automatically and when manually? Why do false alarms occur and why do sirens sometimes not sound when rockets are fired?

Gili Cohen
Gili Cohen
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Israelis take cover as siren sounds warning of incoming rockets near the Gaza border.Credit: Reuters
Gili Cohen
Gili Cohen

Warning sirens have sounded over 4,000 times in Israel over 45 days of fighting with the Gaza Strip. It only takes a few seconds to operate the sirens; sometimes it is done manually by soldiers while at other times it is automatic.



When an Israel Air Force or Artillery Corps radar identifies a rocket or mortar launch from the Gaza Strip, data such as launch speed and trajectory are transmitted in hundredths of a second to a joint command post of the Home Front Command and the air force. The information makes it possible to determine whether a rocket or a mortar has been launched and where it is likely to fall.

When a launch is identifed as being in the direction of communities near the Gaza Strip, where the warning is only 15 seconds from launch, a siren is sounded automatically. That is the reason the area near the Gaza Strip experiences a relatively high number of false alarms. In other areas, a soldier stationed at a command post decides whether to sound the alarm in a particular area or not.

The Home Front Command currently has 204 siren zones, or “polygons” as the army calls them. They are all residential areas or areas surrounding strategic installations.

A probe into last Tuesday’s strike in Be’er Sheva, which broke the cease-fire, found that the command post responded properly in not sounding the alarm, because the rockets landed near a “polygon” on the edge of the inhabited part of the city. “There were two [rockets] fired at Be’er Sheva and we saw there was no real threat to the city, so we realized there was no reason to sound the siren, “ Maj. Aharon Levy, who is in charge of siren warnings in the Home Front Command, said.

So far, the army says, only a small number of rockets that endangered human life did not lead to the sounding of a siren. The air force notes that the rate of identification of a launch leading to the sounding of the siren is over 99 percent. In some cases during the fighting, sirens were sounded in certain cities because of the danger of falling shrapnel after rockets were intercepted.

With regard to the rocket strikes on unrecognized Bedouin communities, in which Oudeh el-Wadj was killed and two girls and a toddler were injured, a senior Israel Defense Forces officer said, “We protect every gathering of people that we know of, not every Bedouin encampment throughout the Negev.”

As Haaretz published last month, the state does not provide protection against rockets to tens of thousands of Bedouin living in unrecognized communities. When there is no electricity in a village, no siren is sounded and a warning is not always given before a rocket lands in a residential area. The Home Front Command has discussed the possibility of providing additional protection, such as sandbags and small mobile shelters, for unrecognized communities.

The south has more than 65 of the 204 warning zones, about a third of the total. Thus, people living within 40 kilometers from the Gaza Strip receive a more specific warning than residents of the center, for example. That means that a rocket falling in an open area in the center of the country will set off an alarm, while a rocket falling in an open area in Ashdod will not. Moreover, the farther the range of the rocket, the less precise the prediction of where it will explode.



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