Measure change and deliver results

RCM 3 contributes observations to a time series alongside the other spacecraft. Comparing brightness can reveal changing scattering conditions. Interferometric synthetic aperture radar, or InSAR, instead compares the phase of compatible radar signals: their position within the wave cycle. A phase comparison can constrain a change in the signal’s travel path.

That path is along the sensor’s line of sight. A result is not automatically a complete three-dimensional displacement or a purely vertical movement. The observations must be aligned to the same ground locations and interpreted with their orbit and terrain information.

The Alaska Satellite Facility’s phase guide explains two important limitations. Atmospheric changes can affect measured phase, and poorly correlated signals can make a phase difference unreliable. Although that guide is written for NISAR, these general concepts help frame an RCM comparison; its mission-specific products are not RCM products.

A usable result passes through planning, acquisition, downlink, processing, quality review and delivery. CSA coordinates RCM operations with partners; Natural Resources Canada maintains receiving and archive functions, including the Earth Observation Data Management System. The ground service turns observations into accessible products.

Latency is the delay between defined events. A duration measured from downlink to delivery omits the earlier waiting time between acquisition and downlink. A service specification must say where its clock starts. Revisit, acquisition-to-delivery delay and the age of the last usable observation answer different questions.

In an original timeline, an image is acquired at 10:00, received at 10:20 and delivered after processing at 10:50. Acquisition-to-delivery latency is 50 minutes; receipt-to-delivery is 30 minutes. If a reader opens the product at 12:00, the observation is two hours old. Calling all three intervals “30 minutes” would hide information important to a changing scene.

Name the clock before quoting a delay

For a change map, preserve the input identifiers, acquisition dates, satellite and mode, processing version and quality decisions. A later analyst should be able to distinguish a changed surface from a changed algorithm. Keep uncertain regions visible rather than turning missing or low-quality measurements into invented zeros.

A June 30, 2026 Canadian government announcement described a contract for an RCM replenishment satellite, with launch targeted for the early 2030s. That is a dated future plan, not evidence that the additional spacecraft is already operating. The June announcement also describes continuing use of the existing constellation. A design lifetime is a planning assumption, not an automatic shutdown date.

Continuity means more than launching a replacement. An overlap can support comparisons between instruments, and users need consistent documentation and accessible records. When the system changes, identify what has been checked before extending an old trend into the new measurements.