Meteosat First Generation: build a dependable weather watch

Meteosat grew from French planning into a European project adopted by ESRO, ESA’s predecessor, in 1972. Meteosat-1 launched in November 1977. Its geostationary position allowed repeated views of the same broad region, supplying information about cloud systems over Europe, Africa and the Atlantic. Weather observations became available over oceans where surface measurements were comparatively sparse.

Maintaining that capability required more than a successful prototype. Later first-generation satellites, operational funding and a dependable ground system supported continuity. EUMETSAT was created as a specialized operational organization, and control of the orbiting Meteosat satellites passed to it in November 1995. ESA’s development role and EUMETSAT’s operational responsibility were related but distinct.

The original observing system used three spectral channels and a half-hour full-disc scanning cycle. Visible, thermal-infrared and water-vapor information supplied different perspectives on clouds and atmospheric conditions. A sequence can reveal movement and development that one image cannot. Visible imagery needs sunlight, while thermal observations use emitted radiation and can support nighttime monitoring.

The Earth view shown here combines observations from Meteosat 3 and Meteosat 4 on May 16, 1993. The two spacecraft occupied different longitudes, so the composite is not one unprocessed camera exposure from a single location. Meteosat-3’s Atlantic assignment also illustrates international cooperation when European spacecraft helped fill a gap in American weather coverage.

The first generation’s operations extended from 1977 to 2017 across successive spacecraft. Preserved observations can support later climate studies, but an old image does not become a climate trend merely because it has survived for decades. Consistent calibration, sampling and processing are needed when comparing measurements across changing satellites and observing positions.

For a fictional storm study, collect suitably spaced images, retain their timestamps and identify the channels used. Estimate motion from comparable features, then compare the result with other meteorological information. For a climate study, extend the comparison across many seasons and document instrumental changes. The same archive supports different questions when the analysis matches the time scale and measurement history.