Do recreational yachts actually transmit AIS, and can a satellite pick it up?

Most ocean-going yachts voluntarily carry Class B AIS transponders, which broadcast at 2 W on VHF channels 87B and 88B. Satellites with sensitive VHF payloads — such as those operated by Spire or HawkEye 360 — can receive these signals from low Earth orbit at ranges up to ~2,500 km. Coverage is probabilistic rather than guaranteed: a single pass captures a statistical sample, not every vessel.

Why can't a country just subscribe to MarineTraffic or Spire and skip building its own constellation?

Commercially sourced AIS data carries three sovereign risks: the provider can throttle, price, or terminate access (especially under political pressure or sanctions regimes); raw tracking data on your maritime border movements sits on foreign servers subject to foreign law; and the analytics pipeline that flags suspicious behaviour is a black box you do not control. A sovereign constellation lets the state set collection priorities, retain the raw data, and audit the algorithms.

What orbit and satellite class makes sense for this application?

LEO nanosatellite or microsatellite constellations (400–600 km altitude) are the right architecture. They provide sub-90-minute revisit at most latitudes, keep launch and replacement costs low, and can host combined VHF AIS and RF-geolocation payloads on the same bus. GEO is unsuitable: AIS VHF signals fade badly at geostationary range and the single-point geometry offers no Doppler-based position cross-check.

How does satellite AIS differ from coastal AIS base stations?

Coastal base stations receive AIS at line-of-sight range (typically 40–70 km). Beyond that range — offshore passages, open ocean, remote island approaches — there is simply no terrestrial receiver. Space-based AIS (S-AIS) closes that gap by receiving transmissions from orbit, giving a nation complete coverage of its EEZ and declared maritime zones rather than just its harbours and anchorages.

Can this system detect a yacht that deliberately turns off its AIS transponder?

Not directly — a switched-off transponder produces no AIS signal. However, a sovereign capability can pair S-AIS with synthetic aperture radar (SAR) satellites (e.g. ICEYE or Capella) and apply correlation logic: if SAR detects a vessel-sized radar cross-section at a location where no AIS signal is present, that 'dark target' is flagged for follow-up. This fusion approach requires owning or contracting both data streams.

What are the legal boundaries for tracking foreign-flagged yachts?

UNCLOS Article 58 guarantees freedom of navigation in the EEZ, meaning a coastal state cannot interfere with innocent passage simply because it tracked a vessel. However, collecting positional data via S-AIS reception is passive surveillance — entirely lawful — and any vessel within the 12 nm territorial sea is subject to coastal state jurisdiction. Enforcement action offshore requires either flag-state consent or evidence of specific treaty violations (e.g. drug trafficking under the 1988 Vienna Convention).

How many satellites does a sovereign programme need to achieve meaningful coverage of a medium-sized EEZ?

For an EEZ of roughly 1–2 million km² (comparable to Australia's eastern seaboard or France's Atlantic zone), a dedicated constellation of 6–12 LEO S-AIS satellites achieves revisit intervals below 60 minutes at the latitude of interest. A more comprehensive constellation of 18–24 satellites with dual AIS/RF payloads can approach near-continuous coverage. Starting with a 3-satellite pilot provides proof-of-concept at modest cost before scaling.

What is the difference between AIS and LRIT for this application?

Long-Range Identification and Tracking (LRIT) is an IMO-mandated system for SOLAS vessels transmitting position via satellite at 6-hour intervals to a national data centre — it is designed for flag-state and port-state administration, not real-time surveillance. AIS transmits continuously and publicly, making it far more useful for pattern-of-life analysis. Recreational yachts are exempt from LRIT entirely, so S-AIS is the only satellite-based tool applicable to this segment.

4.6.6Live

Yacht & Marine Recreation Tracking

Two sailors on the cockpit of a sailing yacht at sea, looking at a navigation display — Sailors monitor their position and route aboard a racing yacht, relying on satellite tracking for safety and course management.

Satellite Tracking System for Marine Recreation

1
Satellite constellation
GPS/GNSS fixes vessel position every second
2
Signal downlink
AIS and GNSS data relayed to coastal stations
3
Fleet analytics platform
Tracks routes, speed, geofence alerts, logs
4
Skipper & coast guard
Live chart overlay, distress alerts, race data

GNSS satellites pinpoint each vessel continuously, streaming position data to shore platforms that keep skippers and rescue services informed.

Page in the build queue

This application has its place in the atlas. The full page — short and long descriptions, what-matters bullets, sovereignty rationale, and the eight-field architecture block — is being written next.

Maturity reading: Operational systems exist with paying customers. Phase 1 built §4.1 (Maritime Intelligence) end-to-end as the depth-and-format reference. Section 4 is the next section to graduate from scaffold to full content; the rest follow on the roadmap.

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