MSG: Europe's new sentinel in space

by European Space Agency

"Extreme weather conditions have revisited much of Europe this week, with cold and rain descending on the British Isles, snow falling on parts of France, and sweltering heat stifling parts of Bulgaria, Turkey and Greece. The weird weather comes a week after Southeastern Europe was scorched by a heat wave that resulted in at least 38 deaths, until strong winds brought a dip in temperatures on July 7." CNN 13 July 2000.

CNN's report, entitled "Extreme weather returns to Europe", is just one example of the unusual atmospheric conditions that have affected the continent in recent years. Although the climate of Western Europe is generally quite benign and predictable, the number of weather-induced disasters seems to be on the rise. Other examples of so-called "freak" weather conditions over the last 15 years include a "hurricane" in the southern UK; floods in the Netherlands, France, northern Italy, Germany and England; a severe storm that flattened trees across much of France; heavy rain and mudslides in Italy and Switzerland.

Fortunately, the advent of modern satellite technology means that we no longer have to rely on visual interpretation of red sunsets and cloud shapes to be forewarned of what tomorrow's weather will bring. An international mini-flotilla of spacecraft now observes the Earth and sends back a stream of data to meteorological organisations around the globe.

The latest and most advanced of these "eyes in the sky" are the Meteosat Second Generation (MSG) satellites that have been developed by the European Space Agency (ESA) during the recent decade. The first of these powerful weather watchers is scheduled for launch in August of this year.

Although it seems that our weather may be getting more unpredictable as the average temperature of the planet steadily increases, extreme events are still quite rare - the October 1987 "hurricane" in the UK was described as a "once in 200 years storm".

Nevertheless, the social and economic consequences of incorrect weather forecasts can be severe. Not only do these incursions of Mother Nature damage trees and property, but they cause disruption, threaten lives and ruin local economies.

In November 1998, the Worldwatch Institute and Munich Re - the world's largest reinsurer -reported that total global losses from storms, floods, droughts, and fires for the first eleven months of that year came to a staggering $89 billion, nearly 50 per cent higher than the previous record of $60 billion in 1996. In addition to material losses, an estimated 32,000 lives were lost through weather-related events, while 300 million people were displaced from their homes - almost the population of the European Union.

So what can be done? Storms and droughts cannot be prevented, but they can be predicted. This is where modern technology comes to the fore. By placing extremely sensitive instruments on Earth-orbiting satellites such as MSG, meteorologists can continuously monitor changes taking place in the turbulent atmosphere.

In Europe's case, most of the weather arrives from the Atlantic, borne by depressions - low pressure systems carried on the jet stream and the prevailing westerly winds.

Since information from ships and automated weather stations about the atmospheric conditions above the western approaches is relatively sparse, meteorologists have increasingly turned to satellites for the prompt, reliable flow of images and data that can make all the difference between accurate or unreliable forecasts.

Following in the footsteps of the remarkably successful Meteosat series, the new generation MSG satellites will provide an even more capable platform to observe the atmosphere over the Atlantic Ocean, Europe and Africa.

Using the latest, state-of-the art technology, MSG-1 will offer not only a major advance in the monitoring of changing weather patterns over this vast area, but it will also improve storm warnings and long-term forecasts, while contributing significantly to global climate research.

Although the name may not be familiar to the man or woman in the street, Meteosat has been an integral part of European life for the past quarter of a century. More than 300 million people across the continent are shown the colourful images from Europe's space sentinels every day as they tune in to the weather forecasts on TV.

These images and other data have been provided by the Meteosat system since the launch of the first European weather satellite in 1977. In all, seven Meteosat spacecraft have been launched during the past two decades, each of them ensuring almost continuous delivery of images and other services to national meteorological services across Europe and Africa.

The first three Meteosats were solely funded and developed by ESA, and the agency has continued to be responsible for the development of Meteosat hardware to the present day, while the handling of day-to-day operations has been handed over to the European Organisation for Meteorological Satellites (Eumetsat) since 1 December 1995.

Europeans are not the only people to benefit. Meteosat data has been used to improve weather forecasts over the Middle East and the entire continent of Africa, and the satellites have also played a vital role in contributing to the global network of weather satellites that continuously monitors the globe from geostationary orbit, where they hover above the same spot on the equator .

However, in order to keep pace with technological developments and demand for more accurate, long range forecasts, it became clear in the early 1990s that an enhanced version of the Meteosat spacecraft was required. As a result, 17 European countries decided to collaborate to build and operate the Meteosat Second Generation: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Artist's view of Meteosat Second Generation (MSG)
The New Generation

Three MSG satellites are currently planned. They are manufactured by a European industrial consortium led by Alcatel Space Industries, France, under the managerial leadership of the European Space Agency. ESA engineers and scientists have been planning the new satellite since 1984 and started in 1990 to develop the advanced technology for the spacecraft and it's instruments on board. It is the Agency's role to understand the clients' needs and to translate these expectations into new technology. In fact, ESA has taken care of the production process of the satellite and has funded MSG-1 with two third of the initial development costs of total 378 Million Euro.

With this scientific and management expertise, ESA will act as the procurement agent for the MSG-2 and MSG-3 satellites. "Negotiations are currently taking place concerning a fourth satellite in order to ensure at least 12 years of continuous operations," said Gerd Dieterle, MSG Project Manager at the European Space Research and Technology Centre (ESTEC) in the Netherlands. "Meteorologists cannot do without them."

To meet the demand for more frequent and comprehensive data from space by scientists, insurance companies and other commercial users, the new satellites will have many design improvements.

Although the cylindrical MSG will be spin-stabilised like the current generation, the 2,000 kg satellite will be almost three times as heavy as its predecessors. The payload of MSG-1 will include three instruments: two radiometers that can detect light reflected at different wavelengths by the Earth's surface and a Search and Rescue transponder.

The most important instrument is the Spinning Enhanced Visible and Infrared Imager (SEVIRI), an advanced version of the radiometer flown on previous Meteosats. Whereas the older instruments could only measure the radiation from the Earth's surface and atmosphere in three spectral channels - visible light, thermal infrared (heat) and water vapour - SEVIRI will be able to record 12 different wavelengths. This will provide a much wider range of data that can be fed into numerical weather forecast models.

"There have been clear improvements in the accuracy of medium-range forecasts in recent years and we expect them to improve further in the future with the new products from MSG," said Dr. Tony Hollingsworth, Head of Research at the European Centre for Medium-Range Weather Forecasts in the UK.

Eight of the channels will be in the thermal infrared, providing information about the temperatures of clouds, land and sea surfaces. Using channels that absorb ozone, water vapour and carbon dioxide, MSG will also allow meteorologists to analyse the characteristics of different air masses, making it possible to construct a three-dimensional model of the atmosphere.

Meteosat Second Generation will provide eight different sets of infrared imagery

In addition to its multi-spectral capability, SEVIRI will be able to show details just 1 km across at visible wavelengths, compared with 2.5 km for the first generation instruments. Furthermore, it will be able to send back twice as many pictures as the current Meteosats - one every 15 minutes instead of every half an hour.

These advances will result in more precise locations of such features as storm clouds and fog banks, as well as faster, more precise forecasts of thunderstorm development, encroaching storm fronts and other hazardous weather conditions.

One of the most significant advances will be made possible by the ozone channel on SEVIRI, the first on a European geostationary satellite. Depletion of the ozone layer allows harmful ultraviolet light to reach the surface, with an increased threat of skin cancer.

"This will give us an estimate of the ozone levels in the lower stratosphere and will lead to forecasts of UVB dosage later this year for all national agencies," said Tony Hollingsworth.

The much larger size and capability of MSG meant that ESA was able to offer space on the satellite for an important climate instrument known as the Geostationary Earth Radiation Budget (GERB) experiment. Developed by a UK-led consortium that also includes Belgium and Italy, the GERB radiometer will measure solar radiation reflected by the atmosphere and thermal (heat) radiation emitted by the Earth.

By measuring the short wave and long wave radiation from the planet every 15 minutes, GERB will enable scientists to calculate with high accuracy the Earth's radiation budget- the balance between the incoming radiation from the Sun and the radiation returned to space. Until now, this information has only been available in the form of brief snapshots from satellites in low Earth orbit.

The data from GERB will allow European scientists to play a leading role in studies of global climate change, with its implications for food production and natural disaster prediction.

"We will make regular measurements in the hemisphere viewed by the satellite, but GERB has a 50 km x 50 km spatial resolution, so we can also study smaller regions such as the Sahara and the Central Atlantic, looking at processes in the local climate system," explained Professor John Harries, Chairman of the GERB International Science Team.

"With GERB we will also be able to investigate the role of dust and aerosols on the radiation budget," he added. "For example, dust streaming over the Atlantic modifies the radiation budget in the tropics by both reflecting and absorbing outgoing radiation."

MSG-1 will also play a more direct role in saving lives. Its Search and Rescue transponder will receive distress signals from ships and aircraft within its coverage zone and forward them to a ground station so that rescue organisations can be quickly alerted.

In addition to these instruments, MSG will carry an advanced communications payload that will be required for satellite operations, communication and dissemination of data to users. This will include the capability to relay weather data from automated stations on land, ships, buoys or aircraft.

Forecasting the Future

The first of the MSG spacecraft will be launched by an Ariane 5 rocket from Kourou, French Guiana, in August 2002. Once the satellite's onboard engine boosts it into orbit above the equator, it will be placed in a standby position above 10 degrees west while its instruments are checked and calibrated.

After its six-month checkout is completed, MSG-1 will be moved to 0 degrees longitude, swapping places with Meteosat 7, the current operational satellite. One year later, the second MSG satellite will be launched, allowing the first generation to be phased out completely. A third satellite will follow when required (see figure 5).

Since each satellite has a nominal operational lifetime of seven years (two more than the current Meteosats), the new family of spacecraft should provide a cost-effective system that will allow Europe to maintain its leading role in gathering global weather data until at least the year 2012.

Raw data from the satellite will be transmitted to the ground station in Darmstadt, Germany, where it will be processed and returned to the satellite for relaying to users around the world. This will continue the service provided by the Meteosats to operational and research users throughout Western and Eastern Europe, Africa, North and South America, the Middle East and even in the Arctic and Antarctic.

In a few years' time, MSG will be joined by Europe's first polar orbiting meteo-satellite, METOP, creating an even more comprehensive and valuable flow of data to a wide variety of users. METOP will be Europe's new contribution for the World Weather Watch programme and another step foreward to a global understanding of weather.

Europe's new sentinels in the sky will ensure that economic activities such as farming, transport, construction industry, public weather services and tourism will benefit enormously from more accurate weather forecasts that will extend from a few days, to weeks or even seasons.