Partnership with Worcester Polytechnic on Project CHIRP

Partnership letter for Project CHIRP (Cognitive Hardware Identification of Radar Pulses).

Most radar sends out a short, powerful pulse and listens for the echo. That is easy to detect, because anyone with a receiver can hear the shout.

A different class of radar was built to avoid exactly that. Instead of shouting, it whispers across a very wide range of frequencies, almost continuously. Any single sliver of the spectrum carries so little energy that it blends into the background hiss that every receiver already lives with. The radar still works, because it knows the pattern it sent and can reassemble the echo. Anyone listening in does not know the pattern, so there is nothing obvious to grab onto. Engineers call these low probability of intercept waveforms.

These signals "chirp" much like a ball rolling around on a stretched surface into a hole, or if you have ever played with spherical magnets you will notice the "chirping" sound they make as they come together. This particular kind of signal is also one that is found when objects rotate and fall into a black hole or as black holes rapidly evaporate as the frequency emission from the object rapidly increases.

CHIRP signals from LIGO.

Finding these signals is possible and using them as a communications channel is the aim of Project CHIRP. You have to listen for a long time and look for structure rather than volume, the way you might pick out a repeating rhythm inside a noisy room. Researchers have gotten good at this. Published work routinely reports accuracy above ninety percent using machine learning on visual representations of the signal.

Here is the part that gets less attention. Almost all of those results come from a workstation running unhurried calculations on stored data. The situation that actually matters is a small circuit board flying on an aircraft at more than twice the speed of sound, with a fraction of a second to identify what is illuminating it and choose a response.