US Navy used vibration sensing to target silent ships for missile strikes
By Miriam Adler ·
Non-cooperative vessels were reduced to frequencies and 3-D state vectors for weapons fire control during a Navy demonstration program from 1993 to 1996.
Radiant Mist and Radiant Outlaw were not ships or aircraft, but the eyes attached to them. According to a program description mirrored by the FAS Intelligence Resource Program, these were "Low Probability of Intercept Sensors," a US Navy Advanced Technology Demonstration that operated between fiscal years 1993 and 1996. The goal was simple: to see without being seen, and to identify a target without needing to get close enough for the target to realize it was being watched.
Radiant Mist was designed for shipboard use, while Radiant Outlaw took the same sensor suite and packaged it for the air. Both relied on a cocktail of passive visible and infrared sensors, paired with an active laser radar. They were designed to operate at what the record calls "unresolved ranges"—distances where a target is a smudge on a screen, a heat signature, or a mathematical probability, rather than a recognizable vessel or a crew of human beings.
"Unresolved Ranges"
The process described in the FAS file is a clinical progression toward a strike. The system did not wander blindly; it was cued by shipboard radars or Infrared Search and Track (IRST) systems. Once cued, the electro-optic system would passively acquire and track the target. This passive phase is the "low probability of intercept" part of the equation—it is the act of watching while remaining invisible.
Once the target was locked, the system handed the data over to a laser radar for "precision tracking and identification." The output of this sequence was not a photograph or a description, but a "3-D state vector." This vector—consisting of bearing, range, and range rate—was then fed directly into the ship's combat system. The record is explicit about the utility of this data: it was used for "weapons fire control and battle damage assessment."
In the language of the Navy, the target is "unresolved" until the laser radar brings it into focus. But the state vector transforms the target into a set of coordinates. Once the coordinates are established, the target is no longer a mystery; it is a destination for a missile.
Beyond Spatial Measurement
The most unsettling aspect of the program was its attempt to automate the act of identification. The Radiant Outlaw/Mist program developed "expert systems" to perform "autonomous classification." The system could categorize a target using image-based data, range profiles, or vibration sensing.
When targets remained unresolved—when they were too far or too obscured for a visual match—the program found that "vibration sensing produced the best aspect invariant results." This is a critical distinction in the physics of surveillance. Most sensors require a spatial measurement; they need to see the shape, the size, or the geometry of a target to know what it is. Vibration sensing ignores all of that. It does not care about the geometry of the ship or the silhouette of the plane.
Instead, it measures the energy received on the target. By analyzing how a target vibrates, the system can identify it regardless of the angle from which it is viewed. It is a form of identification that bypasses the visual entirely, stripping the target of its physical form and reducing it to a frequency. The record notes that the only limiting factor for this technique is the amount of energy received, not the "targets size or geometry."
Summer of 1996
For years, these sensors existed as technical specifications and laboratory successes. That changed in the summer of 1996. To move the technology into an "operational environment," the Navy integrated the multi-functional system onto a McDonnell Douglas Mast Mounted Sight (NMMS) gimbal. This allowed the sensors to be physically mounted and rotated on a ship, proving that the "expert systems" and the vibration sensors could function in the chaos of the open sea.
The program sought to refine the art of the "non-cooperative identification." In the world of maritime law and naval warfare, a cooperative target is one that identifies itself, that broadcasts its position and intent. A non-cooperative target is an enemy, or perhaps simply someone who prefers to remain silent. Radiant Mist was designed to strip away that silence, using laser radar and vibration to force an identity upon the silent.
While the FAS record provides the technical framework of the demonstration, it leaves the human cost of "battle damage assessment" unexamined. We are told the sensors worked, and we are told how they categorized the "unresolved." We are not told how often the autonomous classification was wrong, or what happened to the targets that were reduced to a 3-D state vector.
Technical details of the program were later presented at the Proceedings of TECOM Test Technology Symposium '97 on March 19, 1997.