Maritime users task satellites to find ships, catch vessels operating with their transponders off, map oil spills, and watch ports and exclusive economic zones. Open water is large and dynamic, so the planning problem is about wide-area coverage and revisit, not single high-resolution chips.
This guide covers how to plan maritime acquisitions: SAR for all-weather wide-area vessel detection, optical for identification, and how to size swath and revisit so a moving target is actually inside the footprint.
A vessel moves between overpasses, so coverage and revisit dominate. Favour wide-swath SAR modes (ScanSAR) to blanket a search box in one pass, and stack multiple satellites to tighten revisit so a contact detected on one pass can be re-acquired on the next.
Set the AOI to the full search area — a shipping lane, a port approach, or an EEZ polygon — and evaluate every pass whose swath intersects it. Sort candidate passes by how much of the area each one covers so you prioritise the acquisitions that actually sweep the box.
SAR is the workhorse of maritime surveillance: metal hulls return a strong radar signature against a dark sea, and radar works through cloud and at night. Use SAR to detect and geolocate contacts across a wide area, including 'dark ships' that have switched off AIS.
Once a contact is localised, optical VHR provides identification — hull type, length, and activity. Plan a follow-up optical pass at low off-nadir and in daylight over the detected position, accepting that the target will have moved, so widen the optical AOI around the predicted track.
Oil on water flattens the sea surface and shows up as a dark slick in SAR imagery, making radar the primary sensor for spill detection and extent mapping in any weather. Plan repeat SAR passes to track drift and growth over time.
Correlate detections with AIS to separate routine wakes and natural slicks from incidents, and use the feasibility plan to schedule the cadence of passes needed to follow a spill through its lifecycle.
Yes — SAR detects the physical hull regardless of whether it broadcasts AIS, so 'dark ships' appear as radar contacts you can compare against the AIS picture to find the gaps.
Wider is usually better for search: ScanSAR-class swaths cover hundreds of kilometres per pass, trading resolution for the coverage and revisit that moving-target detection needs.
Plan the optical pass around the vessel's predicted position and widen the AOI along its likely track, since the target moves between the SAR detection and the optical follow-up.
SAR — oil dampens surface waves and appears as a dark slick in radar, detectable through cloud and at night, with repeat passes to track drift.
Draw your Area of Interest, set the window and look-angle limits, and PassPrediction ranks every feasible pass across all operators — neutrally, in your browser, free to start.
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