Invariant Corporation has announced the successful integration of the FireFLY passive acoustic sensor and its artificial intelligence-driven EO/IR architecture with the Surface to Air Kinetic Engagement (STAKE) counter-unmanned aircraft system, establishing a completely passive sensor-to-effector kill chain for the detection and defeat of unmanned aerial systems. FireFLY is a passive acoustic sensor developed jointly by Invariant Corporation and Hyperion Technology Group.
Danny Levis, Invariant President, stated: “Small UAS have created an urgent need for distributed sensing and affordable defeat capabilities that can operate with maneuver forces in contested environments. FireFLY adds passive acoustic coverage where radar and RF are challenged. By integrating that passive acoustic detection directly with a proven kinetic effector, we’ve completed a sensor-to-effector kill chain that detects and defeats unmanned aerial systems without ever emitting a signal. It gets us from detection to defeat faster, with less equipment and a smaller electromagnetic footprint.”
The integrated capability uses acoustic signatures generated by UAS to detect, classify, and determine the location and altitude of an approaching aircraft without transmitting radar or radio-frequency energy. Track-quality detection data is passed directly to the kinetic system’s command-and-control architecture, providing operators with an actionable track.
The acoustic detection system automatically cues Invariant’s passive EO/IR sensor toward the area of interest. An onboard AI stack, named Drone Vision, then searches the live video, locates the UAS within the image, fuses the data, and maintains target lock as the aircraft moves through the environment, without any operator input required. The resulting track data is passed to the kinetic system’s fire control to develop a refined firing solution.
This layered approach combines the broad-area awareness of passive acoustic sensing with image-based EO/IR AI-enabled identification and tracking performance. Detection, classification, sensor cueing, visual target acquisition, and precision tracking can occur at the edge without an active sensor transmission, reducing the electromagnetic signature of the force.
Unlike traditional radar-dependent architectures, the Invariant solution can maintain continuous awareness without creating an electromagnetic signature that may reveal the location of friendly forces. The system is designed to complement, not replace, radar, electro-optical/infrared, and radio-frequency sensors, allowing commanders to construct a layered architecture appropriate to the mission, terrain, threat, and available resources.
In addition to supporting fully passive engagements, FireFLY can serve as a complementary sensor layer inside broader counter-UAS architectures. When active systems are constrained by radar masking, low-altitude flights, terrain, clutter, or RF-silent control methods, passive acoustic detection can provide an independent alert and cue other sensors or effectors toward the threat.
The integration directly addresses emerging Department of War priorities. Recent DoW experimentation efforts have emphasized combinations of passive and active sensors, portable shooters, AI-enabled command and control, and live data networks. STAKE is an integrated C-UxS system capable of kinetic defeat of Group 1-4 UAS at range utilizing the Advanced Precision Kill Weapon System, providing a cost-effective defeat mechanism at approximately $30,000 per shot.
FireFLY is an acoustic sensor deployed globally that provides acoustic detection of gunshots, rocket and mortar fire, and aircraft, including unmanned aircraft. Utilizing a Sensor Open Systems Architecture, FireFLY is capable of being integrated into any C2 or integrated system.
