Terrestrial processes play a crucial role in the carbon cycle through carbon uptake and respiration associated with vegetation growth, and emissions due to disturbance from both natural processes (e.g. wildfires) and anthropogenic land use change. However, the status, dynamics and evolution of the terrestrial biosphere are the most poorly known elements in the carbon cycle. The major uncertainties are in the magnitude and spatial distribution of both carbon stocks and fluxes, in particular regarding carbon emissions from forest loss and degradation, and uptake due to forest growth.
A fundamental quantity characterizing the amount of carbon in the biosphere is biomass, of which roughly half consists of carbon. Forests contain ~80% of the terrestrial above-ground biomass, so changes in forest biomass due to deforestation, degradation, fire and growth cause globally significant fluxes of carbon. In particular, land use change (mainly tropical deforestation) is estimated to yield 12% of the total annual anthropogenic CO2 loading of the atmosphere, though with a large uncertainty (4.9±3 GtCO2/yr ).
Global, spatially explicit and consistent knowledge on forest biomass and its changes is therefore a basic requirement for characterising the carbon cycle. It is also crucial for approaches to managing climate, such as the United Nations Framework Convention on Climate Change initiative known as Reducing Emissions through Degradation and Deforestation (REDD+), aimed at climate change mitigation through conservation and better management of tropical forests. Biomass is also identified as an Essential Climate Variable.
The most critical forest regions of the Earth where biomass information is needed are in the tropical belt, for two main reasons: (a) the land use change (LUC) and degradation fluxes are dominated by changes in tropical forests; (b) REDD+ is aimed at the developing tropical forest countries, where both lack of knowledge about biomass and the need for forest management are at their greatest. Note that the net tropical LUC is made up of two large components: a source due to deforestation and a sink due to regrowth, and information is required on both.

The Earth Explorer Biomass mission will provide the scientific community with accurate maps of tropical, temperate and boreal forest biomass, including height and disturbance patterns. This information is urgently needed to improve our understanding of the global carbon cycle and to reduce uncertainties in the calculation of carbon stocks and fluxes associated to the terrestrial biosphere.
The BIOMASS mission is designed to provide global forest data, but with a focus on the tropics where our knowledge is weakest and the need most critical. This will allow it to play a key role in reducing the large uncertainties in the land use change flux, and in supporting the Monitoring, Reporting and Verification systems that are needed for successful implementation of REDD+.
It is important to note that BIOMASS is intended not just to deliver a static map of forest biomass but to provide essential information on the dynamics of forests, carbon and climate. Over the 5-year mission lifetime it will provide repeated maps of forest cover and its changes, thus contributing substantially to improving the accuracy of estimates of deforestation rates. In addition, it will be able to measure forest growth in younger forests over large parts of the planet, though not for the slow-growing boreal forests. The required measurements are forest biomass and forest height at resolution of 200 m, and detection of deforestation at 50 m. Global maps of biomass are required with accuracy of 20% (or 10 t ha-1 when above-ground biomass are less than 50 t ha-1). To achieve this Biomass will be implemented as a P-band SAR mission. It will exploit the unique sensitivity of P-band SAR together with advanced retrieval methods including polarimetric interferometry (Pol-InSAR) and SAR tomography to measure biomass, height and disturbances across the entire biomass range every 6 months. The mission will also support important secondary objectives, including sub-surface imaging in arid zones, production of a bare-earth DTM and ice applications.

Airbus UK has been awarded a contract to build the Biomass satellite in March 2016. Since then the Project has successfully passed the Preliminary Design Review and has completed the the build-up of the industrial consortium to develop and manufacture the individual subsystems and units. All subcontractors are under contract and hardware production is under way. An overview of the status of these space segment activities will be given in the presentation. This will be complemented by a debrief on the preparations of the ground segment and an outlook on the overall implementation schedule.

The ESA BIOMASS mission will be the 7th Earth Explorer and its primary objective is to measure the above-ground biomass (AGB) in the world’s forests. It is highly innovative, being the first spaceborne P-band SAR mission, fully-polarimetric on all acquisitions, and providing both polarimetric interferometry (Pol-InSAR) and tomographic data. These will be used in synergy to produce Level-2 maps of biomass at 200 m resolution, forest height at 200 m resolution, and severe forest disturbance at 50 m resolution. The mission will also produce tomographic voxels that provide forest backscatter in 3D for each polarization. The current ESA Level-2 (L2) implementation study focuses on defining and implementing the main algorithms for forest parameter retrieval from BIOMASS data. When the study started, the only demonstrated approaches for estimating AGB from P-band data were essentially empirical and needed substantial amounts of reference data, from in situ plots or calibrated airborne lidar. Another drawback of these approaches was that they were not fully representative of the range of conditions of forested environments, so that generality was of concern. The L2 study has made radical improvements in the approach to estimating biomass based on three key elements: establishment of strong evidence that in tropical forests the backscatter from the canopy region 25-35m above the ground is highly correlated with the total AGB (which can be exploited using the full power of tomography ); the development of interferometric ground cancellation to isolate volume scattering; and the development of an approach to invert the model that minimizes the need for reference data. The development of ground cancellation, in particular, has proved to be huge value, since it removes the effects of environmental variability and contributions unrelated to the forest carried in the ground scattering. Forest height methods are well-developed and are currently focused on optimising the algorithms for the BIOMASS case. The forest disturbance algorithm is based on a likelihood ratio test that estimates whether change has occurred in a time series of polarimetric data at a specified level of significance. This paper will discuss the status of the study and our findings from tests of the algorithms using airborne campaign data and simulated data. It will also describe the current activities of the L2 team, which are devoted to systematic validation of the implemented algorithms.

The BIOMASS mission, selected as the 7th Earth Explorer in the 2013, brings as primary scientific objective the determination of the above ground biomass at global scale.
Two mission phases are envisaged: the tomographic and the interferometric phase. In particular the objective of the first phase is to retrieve information on the forest structure from data. In order to achieve this aim, the tomographic processing exploits phase and amplitude of a stack of seven images and produce a 3D imaging of the forest, while the second phase will exploit three interferometric acquisitions to retrieve the biomass information.

The retrieval algorithms relay on an high interferometric phase quality and on high knowledge accuracy of the sensor position.

BIOMASS exploits a Synthetic Aperture Radar (SAR) sensor in P-band. The phase contributions due to the propagation through the ionospheric medium affect the interferometric phase information carried by the SAR data, and the specified knowledge of the sensor position is in the order of 1 meter.

In this paper, we propose a stack-based methodology to estimate and mitigate the effects of ionosphere in BIOMASS mission exploiting an interferometric approach and, at the same time, perform baseline knowledge refinement.

The suggested method is based on the multi-squint interferometric (MS InSAR) phase. The main phase contributions that are expected in the MS InSAR are: the baseline errors, the ionospheric phase screen and the topographic phase.
Acting as a pre-processing to “clean” the interferometric step, the method aims at estimating the three contributions, remove the first two from each image and preserving the topographic phase, to be used for successive processing (e.g. DEM retrieval).

In the paper we describe the methodology and apply it to simulated data and to (modified) airborne campaign data.
We report the performance in terms of Impulse Response Function (IRF) and Interferometric SAR (InSAR) phase quality.

BIOMASS is ESA’s 7th Earth Explorer mission. The mission was selected for implementation in 2012 and is foreseen for launch in 2022. BIOMASS is implemented as a single platform, repeat pass interferometric P-band SAR mission. The instrument is operated in a simple stripmap mode, acquiring global data in a predefined orbit scenario.
The main objective of BIOMASS is to provide estimates of above ground forest biomass and forest height and its temporal dynamics and disturbances. This information shall greatly reduce the uncertainty of the land component in the global carbon cycle.

Beside these primary objectives, the unique P-band SAR vision of the earth surface will support a range of secondary usages of the mission and yet unforeseen applications. Potential applications of the systematic acquisitions of fully polarimetric, interferometric P-band SAR data include mapping of the topography below forests, the subsurface geology of hyper-arid deserts, the ice structure and the ionosphere.

In this paper we will discuss the pros and cons of Biomass to support these secondary applications. We will show first results from campaign data, review the observation scenario for non-forest domains and provide an outlook on future campaign activities to support the definition of those applications.

Selected as European Space Agency’s seventh Earth Explorer in May 2013, the BIOMASS mission will provide crucial information about the state of our forests and how they are changing [Le Toan et al., 2011]. This mission is being designed to provide, for the first time from space, P-band Synthetic Aperture Radar measurements to determine the amount of biomass and carbon stored in forests [Le Toan et al., 1992]. The data will be used to further our knowledge of the role forests play in the carbon cycle.
Earth Observation platforms play an essential role in the new European Space Agency Earth Observation strategy and in the evolution of the ground segment. Earth Observation Platforms are gradually appearing in Europe, at national level or at European scale, and outside Europe. For example, the Thematic Exploitation Platforms currently developed at European Space Agency are a category of exploitation platforms dedicated to geophysical themes. The Thematic Exploitation Platforms under development are instrumental as pilots to formulate future technical and economical approaches for networking exploitation platforms (European ecosystem of Earth Observation Platforms), which is a central idea of the Earth Observation ground segment evolution.
In this context of an innovative sensor and a changing ground segment, the concept of Mission Algorithm and Analysis Platform dedicated to the BIOMASS mission is proposed. This Mission Algorithm and Analysis Platform will be a virtual open and collaborative environment. The goal is to bring together data centre (Earth Observation and non- Earth Observation data), computing resources and hosted processing, collaborative tools (processing tools, data mining tools, user tools, …), concurrent design and test bench functions, application shops and market place functionalities, accounting tools to manage resource utilisation, communication tools (social network) and documentation.
This platform will give the opportunity, for the first time, to build from a community of user of this new Earth Observation mission around this innovative concept.


[Le Toan et al., 2011] T. Le Toan, S. Quegan, M. Davidson, H. Balzter, P. Paillou, K. Papathanassiou, S. Plummer, F. Rocca, S. Saatchi, H. Shugart and L. Ulander, “The BIOMASS Mission : Mapping global forest biomass to better understand the terrestrial carbon cycle”, Remote Sensing of Environment, Vol. 115, No. 11, pp. 2850-2860, June 2011.

[Le Toan et al., 1992] T. Le Toan, A. Beaudoin, et al., “ Relating forest biomass to SAR data”, IEEE Transactions on Geoscience and Remote Sensing, Vol. 30, No. 2, pp. 403-411, March 1992.