4.6.3 — Maritime Security — maturity: live

Ship-to-Ship Transfer Detection

Identifying vessels conducting unreported cargo transfers at sea — oil, grain, weapons or sanctioned goods — by fusing satellite SAR, AIS correlation and optical imagery.

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Ship-to-ship (STS) transfers are the mechanism of choice for sanctions evasion, illicit oil trade and weapons proliferation at sea. When two vessels rendezvous mid-ocean, disable their AIS transponders and exchange cargo, the entire transaction is designed to be invisible to port-state authorities and treaty monitors. Without persistent, independent satellite surveillance, coastal nations and international regulators are left piecing together evidence weeks after the fact — by which time the cargo has cleared customs under a falsified manifest.

A layered satellite stack closes that gap. Synthetic aperture radar detects vessel proximity and relative orientation regardless of weather or darkness, providing the geometric signature of an alongside transfer. RF survey payloads flag AIS spoofing and transponder gaps in near-real time. Optical follow-up, tasked automatically on suspicious radar hits, yields hull-to-hull imagery sufficient for vessel identification and evidence packages. Fusing all three streams against historical AIS voyage data produces a confidence-scored alert within hours of the event.

For a sovereign operator, the operational outcome is direct: coast guard and navy receive actionable intelligence on which vessels to intercept or flag for port detention, treasury and customs agencies get evidential packages that survive legal challenge, and the nation's exclusive economic zone becomes genuinely enforceable rather than nominally sovereign. Relying on a foreign commercial provider for this intelligence is untenable — a vendor can throttle, delay or decline to deliver data the moment it becomes politically inconvenient.

What matters

AIS manipulation is near-universal in sanctioned STS events; radar and RF must substitute for transponder trust.
The UN Panel of Experts on North Korea documented over 160 illicit STS transfers in a single reporting period, all conducted with AIS dark periods.
Evidence admissibility requires a documented, tamper-evident chain of custody from satellite sensor to legal filing — possible only if the data pipeline is under national control.
Revisit latency below four hours is operationally decisive; a vessel pair separates and disperses within that window.

Sovereignty score: 9/10 — STS detection data is a direct instrument of sanctions enforcement and treaty compliance — any dependency on a foreign vendor embeds a political veto over a nation's ability to act on its own maritime law.

Sanctions regimes enforced by major powers (US OFAC, EU, UN) create situations where a foreign satellite provider may be legally or politically prohibited from delivering imagery that implicates a third-party state — leaving the purchasing nation blind precisely when intelligence is most needed.
Evidence collected through a sovereign pipeline is admissible in national courts and international arbitration; data licensed from a commercial vendor typically carries use-restriction clauses that prevent its submission in legal proceedings without the vendor's consent.
A nation reliant on foreign tasking for STS alerts has no guarantee of priority access during a geopolitical crisis, when illicit transfers are most likely to surge and when the same vendor faces competing government demands from its own state customers.
Domestic control over the data pipeline — from sensor to fusion to dissemination — allows classified intelligence on vessel identities, routes and networks to remain within national security channels rather than passing through foreign commercial infrastructure.

Reference architecture

Payload: Primary: X-band SAR, 1–3 m spotlight resolution, 20 km swath, NESZ ≤ −18 dB; secondary: RF survey payload covering 100 MHz to 6 GHz for AIS, VDES and radar-emission fingerprinting, 2 km geolocation accuracy CEP50; optional EO payload, 1 m panchromatic for visual confirmation tasking.
Bus class: ESPA-class microsat, 120–180 kg wet mass, 600 W payload power; SAR and RF payloads co-hosted on a dual-payload bus to reduce per-pass data gaps.
Orbit: Sun-synchronous LEO at 525–550 km altitude; 16-satellite Walker Delta constellation (8 SAR + 8 RF-primary) providing sub-4-hour mean revisit at mid-latitudes; inclined 97.6° to ensure polar and high-latitude EEZ coverage.
Ground segment: Four-station national network (X-band downlink for SAR raw data, S-band TT&C), positioned for maximum revisit overlap at EEZ boundaries; encrypted crosslinks between stations; SatNOGS-compatible UHF/VHF backup for housekeeping telemetry.
Software & data
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References

IMO Guidelines for Ship-to-Ship Transfer of Cargo (Regulation 40-42, MARPOL Annex I) — IMO sets the international framework for legally notifiable STS operations, including advance notice requirements to coastal-state authorities. Transfers conducted outside this framework are presumptively illicit.
UN Security Council Panel of Experts on DPRK — Annual Report — The Panel documents systematic use of mid-ocean STS transfers to circumvent petroleum and coal sanctions, including satellite imagery evidence of vessel-pairs with disabled AIS. Reports are publicly archived and constitute the primary multilateral evidentiary record.
UNODC — Global Maritime Crime Programme — UNODC's programme identifies STS transfer abuse as a key enabler of drug trafficking and sanctions evasion in the Indian Ocean and Gulf of Guinea regions, and supports coastal-state capacity building for detection.
ICEYE — SAR Satellite Constellation for Maritime Monitoring — ICEYE demonstrates operational use of X-band SAR microsatellites for near-real-time vessel detection, including dark vessel identification and alongside-pair imagery — the sensor class directly applicable to STS event detection.
HawkEye 360 — RF Geolocation for Maritime Domain Awareness — HawkEye 360 clusters of three RF-survey microsatellites detect and geolocate AIS anomalies and transponder-off periods at sea, providing the signal-layer complement to SAR imagery in STS detection workflows.