Geostationary-Satellites

As with EumetCast you receive data from a lot of different satellites, geostationary as well as polar orbiting ones, I first want to give you an idea of the geostationary portion of the data and some of its application ...

General Information:

A space-borne remote sensing system consists of many different parts - two major and very important segments are the satellite itself with its instruments and the ground-station(s) responsible for the mission. Imagine this two aspects as the satellite and its instrumentation representing the "eye" and the ground-segment representing the "brain".

Simply spoken the satellite acquires data which is then transmitted to the ground-station(s) where the data is processed. This processing comprises storing the "raw" data (often called Level-0c data) in an appropriate format and apply the necessary calibration (often called Level-1 data). From this Level-1 data many so called Level-2 products can be derived depending on the issue one is investigating or simply interested in. This products include for example sea surface temperature, cloud heights, radiation budgets or concentrations of trace-gases. From certain instruments in combination with sophisticated retrieval algorithms even vertical profiles of for example temperature or trace-gases can be derived!

Examples of Level-2 data:

The following images have been processed from the visible and infrared channels of Meteosat, GOES-E, GOES-W and MTSAT received on 30.04.2015.

Meteosat-Satellites:

The Meteosat series of satellites (MSG) are geostationary meteorological satellites operated by EUMETSAT. EUMETCast (e.g. the dissemination service provided by EUMETSAT) includes data from Meteosat 7 (Indian Ocean), 8 and 9 and since december 2012 Meteosat 10 (MSG-3).

SEVRI: The "Eye" of METEOSAT:

The MSG system provides accurate weather monitoring data through its primary instrument — the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) — which has the capacity to observe the Earth in 12 spectral channels.

A scan mirror reflects the light from the surface of the Earth through a side opening of the satellite to the telescope (see picture). The satellite rotates around its axis 100 times per minute. During this time the telescope scans a line from east to west. The electronics on board put the individual image points together to form a line. After converting the signal the satellite transmits the image line tho Earth.

After each revolution of the satellite, the scan mirror is moved up to get a new line of the Earth's surface north of the previously scanned one. After 1250 satellites rotations or 12.5 minutes, the satellite has scanned the entire globe once and produced a new image (see images below).

It is composed of 3712 x 3712 pixels for the infrared region and 11136 x 5568 for the visible region.

"True"-Color images:

I had to reduce the resolution of the images for this blog but all high resolution images can be found on the ftp-server!

Generating Airmass RGB:

If we want to generate more sophisticated Level-2 products we have to use software which is dedicated to process satellite data on many channels. GeoSatSignal for example is such a tool - it allows you to define a lot of parameters for generating a wide variety of products. To generate the image displayed below with its information on different airmasses I used a configuration which is described in GeoSatSignal_Airmass_Config.pdf.

If you are interested on the physical background of such images I suggest you take a look on that presentation Airmass_Interpretation_Eumetsat.pdf.

Acronyms used:

MSG - Meteosat Second Generation; GOES - Geostationary Operational Environmental Satellite; MTSAT - Multifunctional Transport Satellites; SEVIRI - Spinning Enhanced Visible and InfraRed Imager

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