Israeli nuclear researchers have developed a micro-copter capable of tracking nuclear radiation in difficult terrain.

The palm-sized drones, developed with funding from the US Department of Energy, were invented in Israel’s Negev Nuclear Research Center, better known as the Dimona nuclear facility, where foreign governments believe Israel developed and may house a nuclear arsenal, Haaretz reported Tuesday.

The micro-copters are essentially undetectable and can collect data on radioactivity emanating from underground sites, even in rugged terrain that can be difficult to reach on the ground or view from space.

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While the miniature drones were developed to track radiation levels at radioactive sites without risking the lives of human technicians, and Israeli officials say they were developed purely for defensive purposes, the applications for Western enforcement of Iran’s nuclear program are clear.

The current model’s built-in travel range is limited. The Israeli drone can travel up to 55 kilometers per hour (34 miles per hour) for up to 20 minutes. But Dimona officials are reportedly working on additional models that could offer greater range.

Citing a scientific paper, Haaretz quoted Dimona officials as saying, “The advantage in the system is in data collection over a large area with problematic topography, synchronized by GPS. Such data can serve to identify anomalies on the ground and to track radiation. The data enable us to distinguish between natural and artificial radiation, and to identify specific isotopes, natural or artificial.”

A test of the system was reportedly conducted in the Nevada desert in 2013, pitting the Israeli detector against an American helicopter equipped with radiation measuring equipment.

Its six propeller arms can carry up to 300 grams (10.5 ounces) of detection equipment.