Seekers and terminal guidance
Modular seekers keep the airframe separate from the job of finding the target. The seeker decides whether a round hits a map coordinate or the target itself, and it removes any need for satellite navigation in the final seconds.
Three terminal guidance modalities
| Seeker | Principle | Mission | Typical targets |
|---|---|---|---|
| EO / IR imaging | Passive electro-optical and infrared imaging with terminal lock-on, independent of GNSS | Precision strike on static point targets | Command posts · ammunition depots · critical infrastructure |
| Anti-radiation homing | Passive homing on hostile radar emissions | SEAD — suppression of enemy air defences, opening corridors for follow-on forces | Search and track radars · SAM batteries · EW emitters |
| Scene-matching terminal lock | Dual uncooled LWIR / visible automatic scene matcher, geometric silhouette match | Steep terminal dive onto hardened structures | Revetments · bridge piers · bunker portals |
All three seeker variants operate completely passively. They emit no radio energy, so hostile electronic support measures have nothing to detect. This passive operating requirement mirrors the low-duty-cycle altimeter constraint detailed in GNSS-denied navigation.
Tonbo TRAP-1 electro-optical and infrared seeker integration
The Tonbo TRAP-1 imaging seeker provides day-and-night target acquisition and terminal tracking without external satellite signals. Fast airframes shorten the defender's reaction time, but terminal accuracy decides whether the target is destroyed. Without terminal visual tracking, a fast missile simply arrives rapidly at an approximate coordinate.
A coordinate fix alone can drift or be spoofed before the round arrives. The TRAP-1 sees the target itself, matching stored target features up to impact, so terminal accuracy does not rest on satellite signals alone.
Speed helps the round survive the way in; terminal sensing makes sure it hits. Apollyon couples high subsonic airframes with terminal imaging seekers because an unguided fast weapon and an intercepted slow drone produce the same operational failure.
Passive anti-radiation homing
The anti-radiation seeker tracks radio frequency emissions from hostile air defence radars and electronic countermeasure systems. Its job is air-defence suppression: hostile surface-to-air batteries must switch off their radars or be hit.
This payload makes layered strike possible. Inexpensive attritable effectors fly ahead of heavy cruise missiles, forcing hostile batteries to switch on their radars and spend their missiles before the main strike arrives. See The Missing Middle.
Terminal scene matching and silhouette lock
On heavy strike rounds like the Hemlock, terminal guidance uses a dual uncooled LWIR and visible automatic scene matcher. At the terminal waypoint, the weapon transitions into a steep high-angle terminal dive profile, matching ground silhouettes against onboard geometric models to achieve a circular error probable of roughly 25–50 metres.
We select uncooled microbolometers deliberately. Cooled thermal detectors offer higher raw sensitivity but require cryogenic pumps, high electrical power, and lengthy cooldown cycles. The matching is classical: edge geometry is correlated against stored reference silhouettes rather than absolute thermal gradients. That keeps the processing small, but it also means the reference has to fit the conditions of the strike — a thermal frame does not match a daylight satellite tile directly.
Per-product seeker fit
| Product | Fit |
|---|---|
| Nightshade ADX-1 | Mk II loitering munition: dual-band EO/IR seeker with onboard automatic target recognition. The target-drone configurations carry no seeker. |
| Hemlock | Dual uncooled LWIR / visible scene matcher for steep terminal dive; CEP ~25–50 m |
| Ahuti | Onboard day/night seeker taking over from ground-radar cueing in the terminal phase; visual or RF lock-on |