TeLEOS: add radar to the regional view

TeLEOS-1 launched in December 2015 as Singapore’s first commercial Earth-observation satellite. Its optical imaging mission was followed by a different sensing approach in TeLEOS-2, launched in April 2023. ST Engineering developed the successor in partnership with Singapore’s Defence Science and Technology Agency, or DSTA. The family joins a continuing demand for useful regional imagery with changing instruments and engineering capabilities.

TeLEOS-2 carries a locally developed polarimetric synthetic aperture radar — open definition. The radar transmits signals and records returned energy, allowing observations without sunlight and through cloud conditions that obstruct an optical view. The launch also carried LUMELITE-4, the separate maritime communications experiment. Sharing a rocket did not give the two spacecraft the same payload or mission: one investigates the surface by radar while the other tests radio data exchange.

An optical image records light in selected wavelength bands. A radar image records echoes whose strength and structure depend on the surface, viewing geometry and instrument settings. Polarimetry — open definition adds comparisons among transmitted and received polarization channels. These are additional measurements to interpret, not the natural colors seen by an eye. Processing choices can assign visible colors to radar information for a useful display.

Imagine a fictional response team with a clear optical scene from Monday and a radar scene from cloudy Thursday. Comparing them may help investigate a changing landscape, but a dark patch in one and a bright patch in the other need not mean damage occurred. The instruments measure different physical properties. A careful comparison identifies the acquisition times and sensing methods, then seeks supporting observations appropriate to the proposed explanation.

Match the observation to the question

The spacecraft is one part of an imaging service. An operator must schedule a target, collect suitable data, return it to the ground, process it and deliver an interpretable product. A request for finer detail can compete with coverage, available contact time and processing demand. A launch photograph documents the beginning of that chain; it does not measure the quality or delivery time of a particular customer’s image.

The lesson from TeLEOS is therefore broader than choosing a better camera. A family can add an instrument with different strengths while retaining a regional application goal. Users should specify the question they need answered and evaluate the resulting product against that question. Optical and radar measurements can complement one another when their differences are understood, and useful conclusions depend on processing, context and verification as well as reaching orbit.