RCM: combine repeat visits with different kinds of evidence

The RADARSAT Constellation Mission, or RCM, is a distinct mission within the broader RADARSAT program. Three satellites launched together on June 12, 2019, and were declared operational that November. Their coordinated radar observations were designed to maintain a useful data supply and improve revisit opportunities. Launching spacecraft and accepting a working observation service are separate milestones.

RCM 1, RCM 2 and RCM 3 share an orbital plane with spacing that helps distribute observations in time. This arrangement supports applications such as maritime surveillance, disaster response and ecosystem monitoring. A constellation is not simply three independent photographs pasted together. Orbit geometry, instrument scheduling, ground reception and product delivery all contribute to whether a user receives a useful observation at the right time.

CSA describes daily revisits on average over Canada and more frequent opportunities in parts of the Arctic. Access means that an observation can be geometrically possible. It does not mean that every possible location is imaged continuously or that every acquired product reaches every user immediately. Instrument modes, scheduling and processing still matter. A local question should be checked against actual acquisition records.

Imagine a fictional emergency with suitable passes at 08:00, 16:00 and midnight. A change beginning at 09:00 could wait seven hours for the next listed opportunity, before any processing or delivery delay. Three passes in a day therefore do not guarantee a three-hour wait. Their timing and the event’s timing determine the relevant interval. This example is illustrative, not an RCM service commitment.

Three passes do not mean continuous viewing

Each RCM satellite carries radar and an Automatic Identification System — open definition receiver. Radar detects returned energy from the scene; AIS receives identification and position broadcasts from participating ships. The two observations are different kinds of evidence. Comparing them can help connect a detected target with a reported vessel, provided the times, positions and uncertainties are compatible.

Suppose a radar target has no matching AIS report in a fictional dataset. That discrepancy warrants investigation, but by itself it does not prove illegal activity or establish a particular vessel’s identity. Reception gaps, timing differences and other explanations must be considered. RCM’s value comes from combining observations responsibly: preserve the source and limitations of each measurement before turning the combined product into a decision.