SARwAIS: combining radar observations with ship reports

SARwAIS connects synthetic aperture radar with the Automatic Identification System — open definition, or AIS, for Philippine terrestrial and maritime monitoring. DOST-ASTI’s February 2022 account describes a ten-percent share of NovaSAR-1 tasking — open definition and data access. The spacecraft, catalogued as NovaSAR-S, launched in September 2018. A share of observing opportunities is a participation arrangement, not proof that the Philippines owns the entire spacecraft.

CSIRO describes a separate Australian share in the same mission. The comparison shows how countries can gain useful observing capability through partnerships as well as through nationally built spacecraft. Each agreement has its own scope. The lesson’s Philippine allocation is a historical documented arrangement, not a promise that every present request can be served immediately or with the same terms.

Radar sends radio energy and measures the returned signal. Suitable radar observations can reveal surface features through clouds and without sunlight, although geometry, surface conditions and instrument characteristics still affect interpretation. AIS carries messages transmitted by vessels, including reported identity and position. A radar detection and an AIS report are therefore different kinds of evidence that can be compared.

Imagine a fictional radar image with twelve candidate vessel detections. Eight have plausible AIS matches after time and location are aligned. Four remain unmatched. That subtraction identifies a group needing further investigation; it does not establish that four vessels committed an offense. Missed messages, timing differences, detection errors and other explanations must be considered. A reported position also needs context rather than being treated as infallible truth.

A match is a comparison

The documented workflow sends satellite data through PEDRO reception, COARE storage and computing, and analysis by relevant teams including DATOS. The SIYASAT portal supported requests for particular areas and acquisition modes, with priority review. A request, an accepted task, a successful acquisition and a delivered analysis are separate stages. Knowing the desired location does not make every orbit pass suitable for every measurement.

For a monitoring question, define the area, time window, useful resolution and evidence needed to evaluate the result. Retain the radar acquisition time and the AIS message time when comparing them. Record uncertainty and the possibility that no reliable match can be made. SARwAIS illustrates the value of combining sources while preserving what each one measures, how it was obtained and which conclusions remain unsupported.