Sentinel-5: global atmospheric observations from a weather platform

Sentinel-5 is an atmospheric spectrometer — open definition hosted on the MetOp Second Generation A series. The first instrument launched aboard METOP-SG A1 in August 2025. The host carries several instruments with different measurement tasks. Sentinel-5’s ultraviolet, visible, near-infrared and shortwave-infrared observations are one contribution to that combined weather and environmental platform.

The host’s polar orbit carries it over different parts of Earth while the planet rotates beneath it. Sentinel-5 is designed for broad global coverage on a daily cycle. That describes the observing strategy, not a guarantee that every location yields a usable retrieval — open definition every day. Illumination, clouds and product-specific quality requirements still affect the available measurements.

The spectrometer observes reflected sunlight across wavelength ranges that contain atmospheric absorption features. Measurements of the solar reference help establish what entered the atmosphere, while Earth observations contain the effects of the intervening path. Processing uses their relationship to retrieve atmospheric constituents. The result depends on calibration and an appropriate treatment of scattering and absorption.

Sentinel-5 continues a line of atmospheric observations that includes Sentinel-5P, but the two are different instruments on different spacecraft. Continuity does not mean simply joining files with similar variable names. Scientists compare calibration, spatial sampling, timing and retrieval methods so that a change in hardware does not masquerade as a change in the atmosphere.

Sentinel-5: breadth and continuity

A fictional investigation of changes across continents benefits from wide geographic coverage. A study of how a plume changes through a European afternoon benefits from frequent regional observations. Sentinel-5 and Sentinel-4 address these complementary needs through different orbital viewpoints. Neither observing pattern automatically supplies every advantage of the other.

When combining their products, identify the variable, acquisition time and area sampled by each observation. Account for differences in sensitivity and quality before treating the maps as interchangeable. The useful comparison is between documented measurements with compatible meanings, rather than between mission numbers. Together, regional sequences and broader daily coverage can support a more complete atmospheric picture.