PR · Overwatch
One sensor.
Two ways of listening.
Overwatch is a passive acoustic threat-detection system. A transient engine captures the Mach shock of a supersonic projectile the moment it passes. A harmonic engine listens beneath it for the propulsion signatures of helicopters and drones, and classifies what it finds. Both run concurrently on the same microphones.
Entirely passive — no emissions, no signature. Detections publish within tens of milliseconds to Slipstream, to any MAVLink ground station, or to your own systems.
System summary
| Sensing | Passive acoustic |
| Engines | Transient + harmonic |
| Targets | Shock · heli · drone |
| Sensors | 1 / 2 / 4 microphone |
| Output | JSON over UDP · MAVLink |
| Latency | < 30 ms event-to-trigger |
01 · Architecture
Two engines,
one feed.
A shock is over in milliseconds; a propulsion signature builds over seconds. The two demand different listeners, so Overwatch runs both — fully isolated from each other, on the same microphones, publishing to the same event channel. A fault in one can never silence the other.
Acquire. Analyse. Publish.
One illustrative sequence, followed through both engines to the event channel.
01 / ACQUIREMicrophone array1 / 2 / 4 microphonesSHARED AUDIO FEED
02 / ANALYSE CONCURRENTLY
Harmonic engine
Accumulating03 / PUBLISH
or your own systems.
Event channel
TRANSIENTShock detectedArrival direction*
EVENT PUBLISHED
HARMONICRotorcraftClassified track
TRACK PUBLISHED
JSON / UDP · MAVLink
To Slipstream, ground stationsor your own systems.
TWO CONCURRENT LISTENERS*Direction depends on microphone configuration.ILLUSTRATIVE SEQUENCE
One passive microphone feed goes to independent transient and harmonic engines. The transient engine detects shock events; directional information depends on the microphone configuration. The harmonic engine accumulates propulsion harmonics into classified tracks. Both publish to a shared event channel. Animation timing and waveforms are illustrative, not live measurements.
02 · Transient engine
The Mach shock.
A supersonic projectile announces itself with a shock wave — the N-wave radiated from its Mach cone. The transient engine detects that event against an adaptive model of the environment's own noise, so thresholds hold up in wind and engine wash. The microphone count sets how much direction you get with it.
Single
FIELDED
Detection
One microphone. A shock event is detected and scored for confidence — enough to trigger an undirected manoeuvre or warn the pilot on the sticks.
- Yes · detection
- — · direction
Dual
FIELDED
Left / right
Two microphones add a directional decision. Overwatch commits to a side only when the geometry supports it — head-on arrivals are reported as uncertain rather than guessed. Enough to break the right way.
- Yes · detection
- L / R · direction
Quad
FIELDED
Full direction
Four microphones in a compact array resolve the full arrival direction of the shock front — azimuth and elevation — for a directed response.
- Yes · detection
- Az + El · direction
Validated on live supersonic fire at instrumented ranges — and re-validated against those recordings on every build.
03 · Harmonic engine
Hear them coming.
Every rotor and engine writes a comb of harmonics into the spectrum — a propulsion fingerprint. The harmonic engine lifts that comb out of the noise, tracks it over time, and matches it against a signature library you control. Unknown contacts are reported as unknown — the system never guesses.
A signature in the noise.
AccumulatingHARMONIC SERIES / f → 7fILLUSTRATIVE · FREQUENCY →
A stylised spectrum shows regularly spaced propulsion harmonics rising above background noise as a track is classified. Not measured data.
Rotorcraft
Helicopters
Kilometre-class
Rotor systems write a strong harmonic signature into the low band. Overwatch detects, tracks and classifies rotorcraft types against a signature library — through wind, engine noise, and even the sensor platform's own rotors.
Fixed-wing UAS
Engine-driven drones
Multi-kilometre
Combustion-engine aircraft project the loudest propulsion signature in the class. Detected and tracked at standoff ranges in quiet ambient, with closing-speed estimation on approach.
Multirotor UAS
Small multirotors
Hundreds of metres
Electric multirotors are the quietest targets. Overwatch holds detection through their rapid throttle changes and manoeuvring — a terminal-warning capability for the last line.
Ranges are indicative figures in quiet ambient conditions; a field calibration campaign is in progress. Classification validated against live aircraft audio.
04 · Outputs
Built to be
built on.
Every detection — shock, helicopter, or drone — publishes as a structured event on a versioned contract: JSON over UDP for integrators, MAVLink for autopilots and ground stations. Live dashboards ship with the system for bring-up, tuning, and operator display.
Linked capability · Slipstream
Paired with Slipstream, an Overwatch detection becomes an evasive manoeuvre without an operator in the loop — the supervisor takes control authority, flies the break, and returns the aircraft to its mission.