Is there a 20th century sensor more iconic than radar? In massive Doppler domes or forever-circling dishes at airports, radar installations scream massive infrastructure and far-reaching perception. Miniaturizing the technology has moved it from fixed installations to inside planes and even smaller versions in cars. This week, the Department of Homeland Security awarded $200,000 in funding for the final testing phase of radar tiny enough to fit on small drones.

Produced by Echodyne of Bellevue, Washington, the radar system is more specifically a Metamaterials Electronically Scanning Array (MESA). In function, it mimics a phased array radar, concentrating on tracking an object precisely as it moves. In a short, silent video, Echodyne demonstrates a MESA system tracking the flight path of a DJI Phantom 4 drones for over 3,300 feet. The tracking traces a path through three-dimensional space and above the tree line, rendering the flight of the basketball-sized drone intelligible.

Phased-array systems can draw immense power and be themselves tremendously large. The Sea-Based X-band radar, for example, sits on an oil rig, is towed into place, has a range limited in theory only by the curvature of the Earth, and exists to track the movement of launched missiles. Consider MESA that opposite end of that spectrum, with a smaller range but designed for much smaller targets, tracking quadcopters along the border instead of ICBMs in space.

“Cost, size, weight and power (C-SWaP) is always a concern when deciding on technology investments,” said Tim Bennett of DHS Science and Technology in a release.

“Legacy radar arrays require an expensive, complex and often heavy phase shifter to direct radar beams. Echodyne developed MESA to electronically steer a radar beam with high fidelity and fast directional changes with lower C-SWaP.”

So far, Echodyne has tested the MESA in scrubland and plains, with the promise that this next phase will see more wooded areas and other environments. This is important as, even if a border wall gets built, drones and other light aircraft provide an easy way to cross the border and either scout paths or drop contraband across multiple terrains. Knowing where the targets are is at least half the battle, and that’s the value in having drones that could track the flight paths of other drones, even if it is currently unclear what range the system will have or what anti-drone countermeasures Border Patrol agents will have that take advantage of the new tracking capabilities.

Besides crossing borders, drones are also used to deliver supplies or contraband into other, difficult-to-access places, like prisons. If MESA becomes a standard feature on small drones used by Homeland Security along the border, it may have to track flights into places like the tent city in Tornillo, Texas, where migrant children are interned by the Department of Health and Human Services.

While currently designed for a border security application, it’s not hard to imagine the same system adopted for use on small military drones. We have already seen the effect of cheap commercial drones in the hands of insurgent forces. Giving Army or Marine drones the ability to track rogue phantoms in flight could protect forces in the field, and lead troops back to the insurgent drone operators.

Echodyne’s award to develop MESA includes training and a class for field agents. There, the agents will learn the extent of what the system can do, and perhaps even about the limitations of what it cannot effect.

Watch the system track a quadcopter below: