Scientists at the University of Sheffield are one step closer to launching a satellite mission to measure the biomass in the Earth's forests. BIOMASS is one of three satellites currently competing to be selected as the next European Space Agency's (ESA) Earth Explorer series.

Each year human activities, such as burning fossil fuels, release around 8 billion tonnes of carbon dioxide into the atmosphere.

Tropical deforestation is thought to contribute around 20% of these emissions, but with huge uncertainties, and the true value may be as high as 30%. A major factor in this uncertainty is that the biomass (of which about 50% is carbon) in the forests that are being cleared is very poorly known. As a result, the BIOMASS satellite has been designed to measure forest biomass and height, forest disturbance and regrowth for all the world's forests at spatial scales of around 50-100 m. This will greatly improve our understanding of current forest resources and also, crucially, will tell us how they are changing.

Professor Shaun Quegan, from the School of Mathematics and Statistics at the University of Sheffield, is the lead scientist on this mission and is working with scientists from around the world to ensure that BIOMASS is successful. A big step towards getting BIOMASS into space occurred in February 2009, after a selection meeting in Lisbon at which six competing missions were presented. Only three survived, one of which was BIOMASS. The next two years will now be spent in critical assessment of the mission, with the aim of getting BIOMASS through the final selection in 2011.

BIOMASS takes advantage of a new opportunity, since before 2003 the radar wavelength it uses (68 cm) was unavailable for Earth Observation because of possible interference with military systems.

However, in 2003 the International Telecommunication Union opened this wavelength for imaging the Earth. This was a key development , since measurements of forests at this long wavelength are very sensitive to biomass.

The BIOMASS team, led by Shaun Quegan of Sheffield and Thuy Le Toan of the Centre d'Etudes Spatiales du Biosphere, Toulouse, responded as quickly as possible, making a proposal that was accepted for preliminary studies by ESA in 2006, along with five other missions measuring different aspects of the Earth's behaviour. These studies confirmed the importance and feasibility of BIOMASS; combined with its importance, this carried BIOMASS through the Lisbon selection and closer to its realisation as a space mission monitoring the health of the Earth's forests.

Professor Quegan commented: "Trees are an enormously important resource for people all over the world, for building materials, energy, biodiversity and air and water quality, as well as having a major impact on climate. This mission is urgently needed to keep track of these resources and to understand how changes in the world's forests affect the planet."

In addition, BIOMASS will be able to give the first chance to see the Earth with the special view provided by this type of radar, and it is expected that it will be able to do much more than measure biomass. For example, the radar will be able to penetrate deep into dry soils and ice, making it able to map the bedrock in places like the Sahara, which is important for mineral exploration and understanding past climates, and to measure ice motion across the globe.