Meteosat Second Generation - Weather Forecasts of Unprecedented Precision
Paris/Le Bourget, 01 June 2001
Satellite images with clouds moving across Europe are familiar to everybody from the daily TV news. These images have been available since the launch of the first European weather satellite of the Meteosat fleet in 1977. For more than 24 years the Meteosat satellites have ensured a reliable and successful supply of data for weather forecasts of unprecedented precision. But the technical possibilities have changed enormously since the Meteosat premiere and the technology of Europe's first-generation weather satellites has aged. Therefore, an international consortium of companies - in which Astrium is also involved - is developing and building a new generation of European weather satellites: Meteosat Second Generation (MSG). Meanwhile the first satellite of this new Generation is finished and will be launched in the beginning of 2002. MSG will further enhance the precision and reliability of short-term weather forecasts, as the new satellite generation will offer the meteorologists a considerably enlarged database for their forecast models. In addition to Seviri (Spinning Enhanced Visible and Infrared Imager), the most important measuring instrument aboard MSG, Astrium will deliver the subsystems for power supply, attitude and orbit control and propulsion.
Precise Weather Forecasts are a Valuable Asset
Reliable weather forecasts not only mean a better quality of life to all of us but also translate into hard cash since there are entire branches of industry to which precise weather forecasts are of decisive importance. One example is the construction industry. Bad weather not only has an adverse effect on many types of work; some activities such as concreting simply must have good weather for a guaranteed period of time.
Another branch of industry relying on precise weather forecasts is the transport sector. Roads can be cleared of ice and snow if timely information is available on bad weather, thus reducing the number of accidents and casualties. On top of this, ecological damage caused by the use of salt and de-icing chemicals is minimized. Furthermore, the amount of pesticides used in the agricultural sector is reduced when the chemicals are not immediately washed off the crops due to the onset of rain.
And not to be forgotten - the power industry. Weather forecasts play a central role in establishing consumption estimates. Pressure in the gas pipelines, for instance, has to be raised in good time before consumption starts to rise. If the consumption does not rise, however, then the unused gas must be liquefied - and this is expensive.
Furthermore, extreme weather phenomena, such as hurricanes or floods, seem to be occurring more frequently than they used to. Man is possibly the cause both of this and the long-term global climate changes Therefore, detailed knowledge of the factors which have an influence on the weather and the climate is more important than ever.
Meteosat - The Fleet of European Weather Satellites
The Meteosat fleet is operated by Eumetsat, the 17-member-state European organization for satellite-based meteorology. The Meteosat satellites are positioned 36,000 kilometers above the equator. Their position is geostationary, i.e. it does not change in relation to a reference point on the Earth.
A Meteosat spacecraft has a cylindrical body on which solar cells for power supply and a telecommunications module are mounted. Inside the cylinder is the satellite's heart - the radiometer. Apart from imaging, the Meteosat satellites fulfill two other functions. They receive environmental and weather data from measuring stations located on ships, aircraft or buoys and forward these data to a central station. In turn, the satellites transmit the weather charts generated by the central station to user stations in over 130 countries. Eumetsat's nerve center is located in Darmstadt, 25 kilometers south of Frankfurt. It controls the satellites and receives and processes their raw data and subsequently returns them to the satellite which acts as a relay station and sends the data on to the user stations worldwide.
Meteosat Second Generation (MSG)
The Meteosat Second Generation (MSG) fleet consists of three satellites to be launched into space in 18-month intervals, i.e. four years. The launch of the first satellite is scheduled for January 2002. As for the first Meteosat generation, only one satellite, the so-called primary satellite, is active. This satellite is deployed in a geostationary orbit above the intersection point between the zero meridian and the equator. The other satellite is in a standby position to take over operations in the case of an emergency.
Once in space, MSG-1 will initially be in the standby position at ten longitudinal degrees west of the seventh and last first-generation Meteosat which will still serve as the primary satellite for the next six months. Then, the two satellites will switch their positions and MSG-1 will start operating as the primary satellite above the Gulf of Guinea, west of Equatorial Africa. One and a half years after the launch of MSG-1, the second MSG satellite will be launched into orbit so that both the primary and the standby satellites are of the second generation. MSG-3 will follow four years later or as required. The MSG satellite has an expected lifetime of seven years. All together, the three satellites are to provide Europe with weather data for at least twelve years. As with Meteosat, MSG also forms part of the worldwide weather observation program of the World Meteorological Organization. This program covers ten geostationary spacecraft from Europe, the USA, Russia, China and Japan which monitor the global weather events. When MSG-1 starts operating next year, it will be the most advanced weather satellite worldwide with state-of-the-art technology on-board.
Like the Meteosat first generation satellites, the MSG spacecraft will stabilize their position in orbit using their own spin movement. They spin 100 times per minute in a counterclockwise direction around their own longitudinal axis which is aligned to the Earth's axis. Each MSG satellite has a mass of 2,010 kg and a 2.40-in-high cylindrical housing with a diameter of 3.20 m. The satellite's power is supplied by eight curved solar cell segments surrounding the housing. One of the segments is provided with a recess for the instruments. The total capacity of the solar cells amounts to 720 watts. The satellites can be launched by the European boosters Ariane 4 and 5.
The Eye of the MSG Satellites: Seviri
The most important measuring instrument on board Meteosat Second Generation is Seviri (Spinning Enhanced Visible and Infrared Imager), a radiometer developed and built by Astrium. This radiometer is a "telescope" which measures the radiation from the Earth in various ranges of the electromagnetic spectrum. Seviri is more powerful than the predecessor model aboard the first Meteosat generation which was also developed by Astrium. The old radiometers recorded three spectral channels, i.e. visible light, infrared and water vapor. Seviri records the radiation in twelve different channels of the electromagnetic spectrum. Thus, MSG offers the meteorologists a considerably more differentiated database for numeric weather forecast models.
However, the Seviri telescope not only provides more precise data but also provides the data more frequently. Compared to the telescopes of the first Meteosat generation which produced a satellite image every 30 minutes, Seviri supplies an image every 15 minutes. This supports the meteorologists in evaluating short-term weather developments. Thus, more precise and faster forecasting of the build-up of dangerous weather phenomena, such as storms, thunderstorms or heavy rainfall is possible. In the event of fog, airports can be warned one to two hours in advance. The resolution of the Seviri telescope is considerably higher than that of its predecessors (1 kilometer compared to 2.5 kilometers in the first generation), thus allowing a more precise location of storm fronts or fogbanks.
Technically, Seviri is a lightweight and compact telescope and scan assembly. The telescope is equipped with three mirrors made of Zerodur, an extremely light glass ceramic material. The scan assembly itself consists of an additional movable Zerodur mirror which is positioned in front of the telescope; it performs a linear scan of the Earth's surface from north to south. The telescope sends the collected radiation to the focal plane where it is divided into twelve different channels of the electromagnetic spectrum and transferred to 42 sensors. The sensors transmit the recorded data to the Functional Control Unit (FCO), the interface to the data transmission system of the MSG satellites. Thus, a new multispectral satellite image will be produced every 15 minutes.
The compact structure of the telescope and the scan assembly enables the use of a large passive cooler which improves the performance of the infrared measuring systems by lowering their operating temperature to approx. -190 ° Celsius. The total weight of the Seviri telescope will not exceed 270 kilograms and its power consumption amounts to approx. 123 watts, i.e. equal to that of two medium-power light bulbs.
MSG Supplies Data for Climate Research and Serves as a Relay Station
Seviri is the most important but not the only measurement instrument aboard MSG. The GERB (Geostationary Earth Radiation Budget) instrument of the second Meteosat generation provides important data for climate research. GERB is a radiometer with two broadband channels, i.e. one covering the solar radiation spectrum and the other one the entire electromagnetic spectrum. These instruments will be used for measuring the solar radiation reflected by the atmosphere and the heat radiation emitted by Earth.
Furthermore, the weather satellite is used as a relay station - but not only for sending its own data which have been processed in the Control Center in Darmstadt, to the end user. MSG also receives weather data from measuring stations located on land, ships, buoys and aircraft and transmits them back to Earth.
In addition, a so-called Search-and-Rescue Transponder aboard MSG is in a position to receive emergency signals from ships and aircraft and to transfer them to a central receiving station in Europe. Rescue organizations all over the world can therefore be alerted quickly.
Paris/Le Bourget, June 2001/01012
For further information:
Astrium
Earth observation & Science
Mathias Pikelj
Telephone: ++49 7545 8 9123
Telefax: ++49 7545 8 5589
Börsenkurse
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