Applications as varied as they are surprising

Earth observation from space is leading to a vast array of applications. Some, such as weather forecasting, are well known. Others have a much lower profile. A brief review.

Hurricane Gamede passing over the islands of Mauritius and Réunion on 23 February 2007. Envisat image, Meris spectrometer. Hurricane Gamede passing over the islands of Mauritius and Réunion on 23 February 2007. Envisat image, Meris spectrometer.

Monitoring relations between man and elephant

In Botswana (Southern Africa), nature protection and conservation measures are producing results. The total ban on hunting elephants (Loxodonta Africana) imposed in 1991 has resulted in a continuous increase in the total population of these pachyderms, at the rate of 5% a year. Today this part of Africa is home to the world’s largest concentration of the animal (about 120 000). This abundance, coupled with the inroads made into their natural habitat by the country’s inhabitants who have expanded their arable land, is a new source of conflict between man and elephant. In cooperation with King’s College London, officials at the Centre for Conservation of African Resources: Animals, Communities and Land use (Caracal) in Kasane, consequently launched a major study on the issue, based primarily on satellite imagery. In particular, these data serve to identify the abundance and distribution of elephants over large areas. A single passage by a satellite over a given country gives specialists a global view of elephant populations, enabling them to take any measures needed to protect the interests of either man or elephant.

Forecasting the outbreak of epidemics

Avian flu, cholera, malaria, meningitis… The use of satellites to forecast the spread of epidemics, or tele-epidemiology, is a continuously developing sector. Space observation combined with data obtained in the field make it possible to forecast the spread of epidemics carried by insects or birds, for example. As these carriers are sensitive to environmental changes, by analysing certain satellite data – the earth’s surface, vegetation, wind, cloud cover, sea temperature, meteorological events, etc. – and combining these with various human and animal field measurements, experts are able to forecast how an epidemic is likely to spread and thus envisage the means to combat it. Various tele-epidemiological networks are currently operational in Argentina, Senegal, Niger, China and the Mediterranean Basin.

Antonio Güell of the CNES (French Space Agency) believes these techniques offer unex- plored potential, as their use still remains limited to isolated cases when they could be used systematically to radically improve the health situation in many parts of the world.

Alerting asthmatics

For nearly two years, the London borough of Croydon has piloted a real-time air pollution warning system for people suffering from respiratory complaints. At the end of March 2007, this system, developed by ESA and Cambridge Environmental Research Consultants, was implemented throughout the British capital. Nicky Gavron, Deputy Mayor of London, inaug urated this new service, known as Airtext.

Airtext is an early warning system operated by text messages, voice messages or e-mail. On the basis of air observations from space made by ESA’s Envisat satellite coupled with ground measurements and forecasts on road traffic density, the system sends pollution alert messages to subscribers on the morning of what are expected to be peak pollution days, if not the night before.

This gives subscribers – sufferers of asthma, bronchitis, emphysema, heart disease or angina – the chance to reorganise their day accordingly. It is a warning service that can save lives. Nicky Gavron estimates that a thousand people die prematurely in London every year due to health problems made worse by pollution peaks.

Quality farmed salmon

The world’s leading producer of farmed salmon is located… in the Southern Hemisphere! The country is Chile, its many fish farms currently producing the world’s largest share of farmed salmon. Yet it is an industry that remains fragile and at the mercy of any sudden deterioration in seawater quality – something that happens regularly and naturally. One such instance takes the form of a massive eruption of phyto - plankton, known by the experts as a blooming of microscopic algae. This green tide absorbs a large part of the oxygen available in the water, thereby posing a threat to the salmon. The emission of chemical compounds can also poison other marine species of economic value, such as shellfish and mussels.

It was to forecast this kind of event and monitor it in near real time that the CAP project (Chilean Aquaculture Project), supported by ESA, was set up. Water quality and phytoplankton eruptions are monitored from space using the Envisat satellite (with its Meris radiometer) and the Modis instrument on board the US Aqua satellite. These principally study changes in seawater colour (caused by chlorophyll), turbidity, suspended matter and surface temperature. The data, coupled with hydrodynamic models (ocean currents), are a new management tool for the Chilean fish farming industry.

Tracking the giant waves

Everybody remembers the murderous tsunami that raced across the Indian Ocean on 26 December 2004, following an undersea movement of tectonic plates.

Yet we forget that every year – indeed almost every week – giant waves rise up and break in the oceans of the world as a result of particular weather conditions, mainly storms.

Sometimes known as “rogue waves”(1), these giant waves, with the potential to sink huge cargo vessels, usually disappear without trace. But just last May, one of these “monsters”, towering to a height of almost 11 metres, crashed onto the French island of Réunion, in the Indian Ocean. Despite surveillance from space, the wave submerged the port of St-Pierre in the south of the island, killing two fishermen, destroying several quays and flooding houses and shops. Forecasters had underestimated its intensity.

This giant wave had developed south of the Cape, in South Africa, travelling northeast for almost 4 000 km to hit the island three days later. It was detected and tracked by the Envisat satellite and its ASAR (Advanced Synthetic Aperture Radar) which is able to transmit small images (10 by 5 km) of the ocean surface, taken every 100 km throughout the satellite’s orbit.

These images provide us with information on the height of individual waves. They are then mathematically processed to obtain energy and direction averages known as ocean wave spectrums that ESA makes available to scientists and meteorological stations. Without this routine surveillance, there is every reason to believe that the wave that hit Réunion would have taken a much heavier toll.

Anticipating the ‘greening’ of Greenland

If the icecap that covers Greenland were to melt completely, sea levels worldwide would rise by an average of seven metres. It is a prospect that brings home the importance of monitoring this fragile icecap, one more sensitive to global warming than Antarctica.

The DMC (Disaster Monitoring Constellation) consortium of four Earth observation satellites – belonging to Algeria (Alsat-1), Nigeria (Nigeriasat), Turkey (Bilsat-1) and the United Kingdom (UK-DMC) – is contributing to a study on the melting of the Greenland icecap. These satellites enable researchers at Swansea University to measure the thinning of the ice sheet, the water runoff at its rim and, more generally, the dynamic of all the flows the melting process generates.


(1) See RTD info N°42.