How Three Sensors Surface a Vessel of Interest in Australia’s Cable Damage

At a Glance

• Two of Australia’s subsea internet cables, Indigo West and Indigo Central, were damaged inside the Submarine Cable Protection Zone off Perth over the weekend of August 9-10, 2026.
• Australian authorities described “very suspicious activity from a vessel near the location,” and Windward’s multi-sensor analysis surfaced one vessel whose movements align with the timing and location of the damage.
• Three independent sensors — AIS behavioral history, electro-optical and synthetic aperture radar imagery — each captured the vessel at different points in the window during which the cables were cut.
• No single sensor is decisive on its own, since AIS tracks alone can be manipulated, EO imagery proves presence at a specific moment rather than behavior across time, and SAR returns are technical signatures rather than visual images.
• Stacked together, the three sensors produce a picture that is analytically defensible, with three independent sources capturing one vessel, on the cables, at the time of the cuts.
• Fewer than 20 subsea cables carry roughly 99% of Australia’s internet traffic, and protecting them starts with knowing which vessel was there and being able to prove it defensibly.

What Happened Off Perth

Over the weekend of August 9-10, 2026, two of Australia’s subsea internet cables, Indigo West and Indigo Central, were damaged inside the Submarine Cable Protection Zone off Perth. Owned by SUBCO, the cables form part of the infrastructure carrying international internet traffic between Australia and Southeast Asia.

Australian authorities cited “very suspicious activity from a vessel near the location.” No specific vessel has been publicly named or formally attributed by the Australian government. What is publicly known is that the damage occurred in a designated protection zone, that the cables were commercial internet infrastructure, and that a vessel was operating in the area under conditions that drew the attention of the investigating authorities.

Windward’s multi-sensor analysis surfaced one vessel whose movements align with the location and timing of the damage. Three independent sensors captured that vessel at different points in the relevant window. Each sensor, on its own, would leave room for argument. Together, they produce a picture that does not.

What AIS Showed

The vessel’s AIS behavioral history over the weeks preceding the damage exhibits a pattern that would draw analytical attention on its own.

The vessel entered Australia’s Exclusive Economic Zone on July 28, 2026, anchored off Perth, and remained in the area for nearly two weeks. On July 31, her declared ETA changed to January 1, 2027, a placeholder value typical of vessels with no genuine port call intent. Through August 8-9, the window during which the cables were damaged, its AIS track shows repeated erratic crossings over the cable corridor.

AIS alone is not enough to build a case. An activity timeline like this can be explained away. A vessel loitering near infrastructure could be waiting for berth, conducting legitimate operations, or experiencing operational delays. An ETA changed to January 2027 could be a system default. Erratic crossings could be weather-related.

Any AIS pattern can be argued with in isolation. What AIS provides is the behavioral thread that other sensors can be tested against.

What Electro Optical (EO) Satellite Imagery Showed

On August 3, 2026 at 02:12 UTC, electro-optical (EO) imagery captured the vessel roughly 11 kilometers west of Perth, off Marmion Marine Park.

EO imagery provides visual confirmation that the vessel was where the AIS record said it was. Windward’s high-resolution EO can resolve down to 30 centimeters, supporting vessel identification through distinguishing features.

However, EO alone is limited. It proves presence at a specific moment, but it does not prove behavior across time. A single EO frame captures a vessel at one point, not what the vessel did before or after. In addition, EO imagery depends on daylight and clear conditions, which limits when and where it can be captured.

An EO frame is the strongest single confirmation of presence. It is not, on its own, a picture of activity.

What Synthetic Aperture Radar (SAR) Imagery Showed

On August 8, 2026 at 21:42 UTC, synthetic aperture radar (SAR) imagery placed the vessel directly on the cable route.

SAR is a sensor that does not depend on daylight, weather, or the vessel’s own broadcasts. It works in darkness, through cloud cover, and it detects vessels whether or not they are broadcasting AIS.

SAR returns are technical signatures rather than visual images. A trained analyst can read them, but a non-specialist looking at a SAR return sees a bright smudge on a purple field. On its own, SAR proves presence at a specific time and location, but it does not prove intent, and it does not communicate as visually as EO.

SAR is the sensor that closes the temporal gap. It captured the vessel on August 8, directly on the cable route, during the window in which the cables were damaged.

Any One of These Signals Can Be Argued With

This is the analytical point that matters.

An AIS track can be dismissed as noise. Loitering, ETA changes, and erratic crossings all have possible explanations that do not involve deliberate action. An EO frame proves presence at a moment but not behavior across time. A SAR return is a bright signature on a purple field, decisive to an analyst but easy to challenge in a public or legal context.

Stack them and the ambiguity collapses. Three independent sensors, drawing on entirely different physical principles, each captured the same vessel at different points in the same window. AIS documented the behavioral pattern, EO documented visual presence, and SAR documented presence on the cable route during the damage window.

No single sensor is decisive. Together, they produce a picture that is defensible.

Why This Matters for Cable Protection

Fewer than 20 cables carry roughly 99% of Australia’s internet traffic, according to Michael Shoebridge of Strategic Analysis Australia. Australian Defence Minister Richard Marles warned at the 2026 Shangri-La Dialogue that “the seabed was becoming a battlefield.”

The Indigo cables connect Perth to Singapore and Jakarta, carrying commercial internet traffic. When they are damaged, the traffic reroutes through remaining infrastructure. Repair takes weeks, and averaged 40 days in 2023. Every incident of this kind demonstrates that cable protection is not something that can be delegated entirely to the physical protection zone. It requires knowing which vessels are operating near critical infrastructure, how they are behaving, and being able to attribute activity when incidents occur.

Attribution matters legally, diplomatically, and operationally. If a vessel damaging critical infrastructure cannot be identified, the incident cannot be responded to in a way that deters repetition. The specific vessel identified through multi-sensor analysis is what enables the response, whether the response is regulatory, diplomatic, or legal.

How Windward Supports Critical Maritime Infrastructure Protection

Windward’s Critical Maritime Infrastructure Protection (CMIP) capability is built for exactly this analytical work. Cable operators, naval maritime operations centers, and government agencies responsible for subsea infrastructure protection use CMIP to monitor vessel activity near critical assets, detect behavioral patterns that indicate potential threats, and reconstruct events when incidents occur.

The core capability is active threat detection. The operator provides the coordinates of the cable infrastructure. Windward’s platform applies all-source operational intelligence to monitor a defined polygon around those coordinates continuously, using satellite imagery, radio-frequency detections, behavioral pattern recognition, and other sources to monitor vessel activity within the zone. When a high-risk vessel exhibits suspicious behavior near the infrastructure, an alert is sent to the operator’s team.

The Indigo case is a demonstration of what that picture looks like when it matters. The analytical work does not end with identification. It supports the regulatory, diplomatic, and operational response that identification enables.

Researched by Windward’s MIOC analysts. Written by Maya Romi, Maritime Intelligence Content Specialist, Windward.