Résumé
Tropical forests are a key component of the global carbon cycle. Yet,
there are still high uncertainties in forest carbon stock and flux
estimates, notably because of their spatial and temporal variability
across the tropics. Several upcoming spaceborne missions have been
designed to address this gap. High-quality ground data are essential for
accurate calibration/validation so that spaceborne biomass missions can
reach their full potential in reducing uncertainties regarding forest
carbon stocks and fluxes. The BIOMASS mission, a P-band SAR satellite from
the European Space Agency (ESA), aims at improving carbon stock mapping
and reducing uncertainty in the carbon fluxes from deforestation, forest
degradation, and regrowth. In situ activities in support of the BIOMASS
mission were carried out in French Guiana and Gabon during the TropiSAR
and AfriSAR campaigns. During these campaigns, airborne P-band SAR, forest
inventory, and lidar data were collected over six study sites. This paper
describes the methods used for forest inventory and lidar data collection
and analysis, and presents resulting plot estimates and aboveground
biomass maps. These reference datasets along with intermediate products
(e.g., canopy height models) can be accessed through ESA's Forest
Observation System and the Dryad data repository and will be useful for
BIOMASS but also to other spaceborne biomass missions such as GEDI, NISAR,
and Tandem-L for calibration/validation purposes. During data quality
control and analysis, prospects for reducing uncertainties have been
identified, and this paper finishes with a series of recommendations for
future tropical forest field campaigns to better serve the remote sensing
community.