The Earth is clearly in focus
The new SEVIRI “weather eye” photographs the same quarter of the Earth’s surface every 15 minutes. The radiation reflected from the Earth’s surface and the atmosphere is collected by a mirror and reflected in the direction of the telescope and the detectors. A series of images thus shows the development and changes in the weather in this particular region. All this is possible because the MSG-1 satellite is in geostationary orbit, which means that it revolves around the Earth at the same speed as it rotates on its axis. That is why it appears to stand still above the Earth. In fact, the MSG-1 is positioned over the western coast of Africa, some 36,000 kilometers above the equator. From here it has a clear view of Europe, Africa, parts of the Indian Ocean and all of the Atlantic Ocean. The Atlantic plays a crucial role because the weather in Western Europe largely originates from there.
The SEVIRI radiometer measures the reflected radiation in 12 different spectral channels. Each channel – four of which are in the visible range and eight in the ultraviolet range – provides different data. They vary from visible images of the weather occurrences during the day and cloud temperature at night to surface temperatures and water vapor measurements to determine gas and dust particle concentrations in the atmosphere.