4.1.5 — Maritime Intelligence — maturity: live

RF Geolocation of Vessels

Detecting and geolocating vessels by their radar, satellite-phone and other radio-frequency emissions — including those that have switched off AIS.

Modern ships emit a forest of radio signals: navigation radar, satellite phones, marine VHF, radar transponders, even crew Wi-Fi access points. Switching off AIS does not silence any of these — they are operationally essential for the ship to function. A constellation of satellites flying in tight formation can detect those emissions, time-stamp the moment each receives the signal, and triangulate the emitter's position by time-difference-of-arrival. The geolocation accuracy is on the order of hundreds of metres to a few kilometres — useless for a torpedo, decisive for cueing a SAR satellite or a maritime patrol aircraft.

The reference operator is HawkEye 360, which flies clusters of three smallsats in formation; competitors include Unseenlabs (France) and Kleos (now wound down). HawkEye 360's data is integrated into the US Department of Defense Indo-Pacific awareness picture and was sold to India in May 2025 in a USD 131M Foreign Military Sale package alongside the SeaVision platform — explicit confirmation that the capability is treated as sovereign-relevant. For middle-power coastal states the appeal is direct: foreign navies, sanctions evaders and IUU fishing fleets all light up the spectrum even when they are AIS-dark.

What matters

RF emissions are operationally hard to suppress without crippling the vessel — making this the most reliable non-cooperative tracking method available today.
The sensor is fundamentally a cluster: physics requires precise formation flying for time-difference-of-arrival geolocation.
HawkEye 360 has demonstrated a 36-satellite operational constellation and an exit path (S-1 filing for IPO in April 2026); this is a proven business pattern, not a science project.
Indian, GCC, and African government interest is real and budgeted — the May 2025 India FMS is a published reference point.

Sovereignty score: 9/10 — Critical.

RF SIGINT is in the same conceptual category as ELINT — an explicit intelligence capability — and foreign supply means the supplier sees what you see.
Even friendly suppliers gate access (the FMS process to India is the proof point — capability arrives with conditions).
Building an RF cluster is genuinely achievable at smallsat scale; no exotic physics involved.

Reference architecture

Payload: Wideband passive RF receiver (covering at least L-band through X-band — marine VHF, satphone uplinks, navigation radars). Precise time reference (GNSS-disciplined oscillator or chip-scale atomic clock).
Bus class: 16U–25 kg microsat with reaction-wheel attitude control and a small propulsion system for formation maintenance.
Orbit: 500–600 km SSO LEO, three-satellite cluster geometry (typically 100–500 km along-track baseline). Operational coverage: 5–7 clusters (15–21 sats) for global ~hourly revisit; 10+ clusters for sub-hourly.
Ground segment: Sovereign ground station for tasking and downlink of geolocation-grade RF data; commercial GSaaS for non-sensitive housekeeping.
Software & data
Latency
Cost band
Lead time

References

U.S. Navy renews HawkEye 360 contract for Indo-Pacific MDA — operational use of RF geolocation for maritime intelligence.
HawkEye 360 — overview, constellation status, India FMS — documents the 36-Hawk-satellite operational constellation, the Maxar RF Solutions acquisition, and the USD 131M India sale.