Ocean currents play an important part in regulating the Earth’s climate. Driven by the density and the salinity of the water, they transport warm and cold water around the globe. Soil moisture is another determining factor because there is a direct link between soil moisture and the humidity of the atmosphere. Mapping global soil moisture will contribute to understanding the earth’s water cycle.
SMOS – the “Soil, Moisture and Ocean Salinity” project aims to do just this: to investigate the source of all life on earth – water. Says Achim Hahne, the SMOS Project Manager at ESA (The European Space Agency): “The importance of the SMOS mission is in the first place that we are supporting science. That means we are furthering the understanding of how our own world is working, of how our climate it working, how it is changing; either naturally or by the impact of men. Eventually we hope that by demonstrating the possibility of doing these measurements, that it will become an operational mission which is used by weather services, disaster monitoring agencies and so on…” To take accurante measurements of the amount of salt in the oceans and the amount of water in the soil scientists would need to use an antenna with a diameter of 20 metres, but something that size would be impossible to put into orbit. That is why SMOS has spent ten years developping a new instrument which has three arms covered with a total of 69 small antennae. These act like one big antenna and make a 2-dimensional interferometric radiometer. The satellite doesn’t actually look for salt. It charts the radiation of the oceans and then looks for the electric characteristics. Because the conductivity of the water is influenced by the salinity, the satellite is able to measure the amount of salt in it. The SMOS satellite can detect 0.1 gram of salt in a litre of sea water. Says Yann Kerr, from CESBIO in Toulouse: “The satellite goal, in terms of soil moisture, is to get access to global coverage of the humidity in the first centimetres of the soil, all over the globe, every three days maximum.” The continuous exchange of water between the oceans, the atmosphere and the land is one of the most important processes controlling the Earth’s climate, but it is still relatively poorly understood. Data on the two variables, soil moisture and ocean salinity, has been sparse and often incomplete. But now, scientists will finally have accurate data. Says Susanne Mecklenburg, the SMOS Mission Manager at ESA: “The SMOS mission actually, directly corresponds to the current lack of global measurements of those two variables. And in addition to that we also have an objective to provide data for cryospheric scientists, but that’s a secondary objective in the mission design. However we strive to correspond to that one too and always thinking that there is, of course, many dedicated missions on atmospheric aspects too.” Once in orbit, the SMOS satellite will collect data that will not only enable scientists to understand the way our planet works, but will also enable them to forecast the weather more accurately. The launch is planned for 2nd November. For more information see: http://www.esa.int/esaLP/LPsmos.html