Lead Research Organisation: University of Sheffield
Department Name: Mathematics and Statistics


Knowledge about forest above-ground biomass and how it is are changing is of fundamental importance in quantifying how the Earth's carbon cycle and climate behave, and is also crucial in assessing forest resources and the services they provide to mankind. For most parts of the world, in particular the tropical forests, information on biomass is currently very limited, at very coarse scales, and subject to large and unquantified errors. Getting a better handle on the biomass in these forests is therefore an essential part of knowing how forests contribute to climate change and supporting UN negotiations on measures to protect them. In response to this urgent need, an international team led by UK and French scientists proposed the BIOMASS satellite mission to the European Space Agency for the third cycle of Earth Explorer Core missions. In competitive assessments, this was first selected to be one of six missions out of 29 proposed for further study, and in March 2009 was one of the remaining three selected for Phase A Study. If all goes well and BIOMASS passes a further assessment in 2011, it will launch in 2016-17. Over the five-year mission lifetime, it will map the full range of the world's above-ground biomass with accuracy and spatial resolution compatible with the needs of national scale inventory and carbon flux calculations, and will map changes in forest biomass. These data are crucial for improving our assessments of the current and future carbon cycle, and have important ramifications for the water cycle and human use of the biosphere. The mission also has several important secondary objectives, including gathering new information on polar ice, soil moisture, ocean salinity, and sub-surface structures and palaeo-hydrology in arid areas. BIOMASS takes advantage of a new opportunity, since before 2003 the long 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. However, along with the special capabilities of long wavelength radar come special problems. In particular, the radar signals used by BIOMASS have to travel through the ionosphere, which can affect them in a variety of ways. Hence a key step in ensuring the selection and success of BIIOMASS is to develop strategies for dealing with these effects. Part of this strategy is to choose the orbit carefully, because the ionosphere varies enormously with position, time of the day and year, and conditions on the Sun. So we can choose an orbit that reduces the effects; to do this requires extensive knowledge about ionospheric behaviour, and part of the research will be devoted to building up this knowledge and relating it to radar performance. However, it is clear that there are conditions under which we will need ways to correct the data, and much of the research will be devoted to developing and testing methods to do this. Its end point will be a set of procedures that tell us how make accurate measurements of forest biomass and height under whatever ionospheric conditions BIOMASS encounters, and thus ensure the mission can deliver its ambitious science goals.


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Chen J (2010) Improved Estimators of Faraday Rotation in Spaceborne Polarimetric SAR Data in IEEE Geoscience and Remote Sensing Letters

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Jie Chen (2011) Calibration of Spaceborne CTLR Compact Polarimetric Low-Frequency SAR Using Mixed Radar Calibrators in IEEE Transactions on Geoscience and Remote Sensing

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Rogers N (2014) The Accuracy of Faraday Rotation Estimation in Satellite Synthetic Aperture Radar Images in IEEE Transactions on Geoscience and Remote Sensing

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Rogers N (2014) Impacts of Ionospheric Scintillation on the BIOMASS P-Band Satellite SAR in IEEE Transactions on Geoscience and Remote Sensing

Description This work was carried out to support the scientific case for the ESA BIOMASS mission, whose purpose is to measure the biomass of the Earth's forests globally at scales of around 4 ha. This is of fundamental importance for estimating carbon emissions due to tropical deforestation and forest degradation, as well as providing unprecedented information on the extent and changes of forest resources across the globe. Against very strong competition from two other candidate missions, BIOMASS was selected by ESA in 2013 as its 7th Earth Explorer, to launch in 2020.The key technology involved is a long wavelength radar (68 cm or P-band), but this wavelength is strongly affected by the ionosphere. The purpose of this research was to characterise the associated effects on the ability of BIOMASS to meet its mission objectives, and to find ways to mitigate or correct the effects. The two most important effects are Faraday rotation, which distorts the polarization measurements critical to the mission, and ionospheric scintillation, which defocuses the radar. These are both connected with calibration of the instrument to ensure it makes true measurements. This research made major steps on all three issues. We developed a new method to correct Faraday rotation. A crucial contribution was our demonstration that an orbit that strays not too far from the dawn-dusk meridian at the equator will encounter negligible disturbance from scintillation except at high magnetic latitudes. Hence BIOMASS measurements over forests will be unaffected, except in the boreal forests of N. America. However, high latitude ice measurements will be seriously affected. This may be mitigated by new methods that use high precision Faraday rotation measurements to learn the phase fluctuations across the radar phase-front.
We also developed and published a calibration scheme suitable for the BIOMASS mission.
Exploitation Route This work underpinned the selection by the European Space Agency of the BIOMASS mission as Earth Explorer 7 to be launched in 2020. It will also provide the basis for the mission planning, ionospheric correction and calibration.
Sectors Aerospace, Defence and Marine,Environment

Description In March 2013 the European Space Agency (ESA) selected, against very strong competition, the BIOMASS mission as its 7th Earth Explorer, for launch in 2020. This is the first space mission using P-band (wavelength 70 cm) radar, which gives the capability to provide global maps of forest biomass and height every 6 months during the 5-year operational lifetime, at 200 m resolution and with an accuracy of 20% for biomass and 20-30% for height. Crucial for selection was our demonstration that the accuracy and resolution requirements could be met in the presence of disturbance from the ionosphere. This finding underpins ESA's decision to select BIOMASS at a cost of €470M, with €280M going to industry, and with far-reaching impacts for science, policy, the environment and society.
First Year Of Impact 2013
Sector Aerospace, Defence and Marine,Environment,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic