The BIOMASS mission: Mapping global forest biomass to better understand the terrestrial carbon cycle
Journal article, 2011
In response to the urgent need for improved mapping of global biomass and the lack of any current space
systems capable of addressing this need, the BIOMASS mission was proposed to the European Space Agency for
the third cycle of Earth Explorer Core missions and was selected for Feasibility Study (Phase A) in March 2009.
The objectives of the mission are 1) to quantify the magnitude and distribution of forest biomass globally to
improve resource assessment, carbon accounting and carbon models, and 2) tomonitor and quantify changes
in terrestrial forest biomass globally, on an annual basis or better, leading to improved estimates of terrestrial
carbon sources (primarily from deforestation); and terrestrial carbon sinks due to forest regrowth and
afforestation. These science objectives require the mission to measure above-ground forest biomass from 70° N
to 56° S at spatial scale of 100–200 m, with error not exceeding ±20% or ±10 t ha−1 and forest height with
error of ±4 m. To meet the measurement requirements, the mission will carry a P-Band polarimetric SAR
(centre frequency 435 MHz with 6 MHz bandwidth) with interferometric capability, operating in a dawn-dusk
orbit with a constant incidence angle (in the range of 25°–35°) and a 25–45 day repeat cycle. During its 5-year
lifetime, the mission will be capable of providing both direct measurements of biomass derived from intensity
data and measurements of forest height derived from polarimetric interferometry. The design of the BIOMASS
mission spins together two main observational strands: (1) the long heritage of airborne observations in
tropical, temperate and boreal forest that have demonstrated the capabilities of P-band SAR for measuring
forest biomass; (2) new developments in recovery of forest structure including forest height from Pol-InSAR,
and, crucially, the resistance of P-band to temporal decorrelation, which makes this frequency uniquely
suitable for biomass measurements with a single repeat-pass satellite. These two complementary
measurement approaches are combined in the single BIOMASS sensor, and have the satisfying property that
increasing biomass reduces the sensitivity of the former approach while increasing the sensitivity of the latter.
This paper surveys the body of evidence built up over the last decade, from a wide range of airborne
experiments, which illustrates the ability of such a sensor to provide the required measurements.
At present, the BIOMASS P-band radar appears to be the only sensor capable of providing the necessary global
knowledge about the world's forest biomass and its changes. In addition, this first chance to explore the Earth's
environment with a long wavelength satellite SAR is expected to make yield new information in a range of
geoscience areas, including subsurface structure in arid lands and polar ice, and forest inundation dynamics.
ESA Earth Explorer