Abstract
In 2015 and 2016, the AfriSAR campaign was carried out as a collaborative effort among international space and National Park agencies (ESA, NASA, ONERA, DLR, ANPN and AGEOS) in support of the upcoming ESA BIOMASS, NASA-ISRO Synthetic Aperture Radar (NISAR) and NASA Global Ecosystem Dynamics Initiative (GEDI) missions. The NASA contribution to the campaign was conducted in 2016 with the NASA LVIS (Land Vegetation and Ice Sensor) Lidar, the NASA L-band UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar). A central motivation for the AfriSAR deployment was the common AGBD estimation requirement for the three future spaceborne missions, the lack of sufficient airborne and ground calibration data covering the full range of ABGD in tropical forest systems, and the intercomparison and fusion of the technologies.During the campaign, over 7000 km2 of waveform Lidar data from LVIS and 30,000 km2 of UAVSAR data were collected over 10 key sites and transects. In addition, field measurements of forest structure and biomass were collected in sixteen 1-hectare sized plots. The campaign produced gridded Lidar canopy structure products, gridded aboveground biomass and associated uncertainties, Lidar based vegetation canopy cover profile products, Polarimetric Interferometric SAR and Tomographic SAR products and field measurements. Our results showcase the types of data products and scientific results expected from the spaceborne Lidar and SAR missions; we also expect that the AfriSAR campaign data will facilitate further analysis and use of waveform lidar and multiple baseline polarimetric SAR datasets for carbon cycle, biodiversity, water resources and more applications by the greater scientific community.
Highlights
Remote Sensing of Environment 264 (2021) 112533 showcase the types of data products and scientific results expected from the spaceborne Lidar and Synthetic Aperture Radar (SAR) missions; we expect that the AfriSAR campaign data will facilitate further analysis and use of waveform lidar and multiple baseline polarimetric SAR datasets for carbon cycle, biodiversity, water resources and more applications by the greater scientific community
The European Space Agency (ESA) BIOMASS mission will collect data in fully polarimetric, repeat-pass interferometric and tomographic modes to produce repeated measurements of forest height as well as Aboveground Biomass Density (AGBD) during its 5-year mission life (Quegan et al, 2019). These maps are expected to be more accurate in higher AGBD ecosystems than those produced by other SAR missions, due to higher P-band penetration into the canopy compared to shorter wavelengths such as L, C, X or S-band and, more importantly, due to the missions’ capability to support Polarimetric Inteferometric SAR (InSAR) and Tomographic SAR
The released CHMFusion fused canopy height and AGBD products help demonstrate examples of this potential, and the released L1 UAVSAR and LVIS data can be used for development and testing of other future algorithms, which can be applied to spaceborne data from Global Ecosystem Dynamics Initiative (GEDI), National Aeronautics and Space Agency (NASA)-ISRO Synthetic Aperture Radar Mission (NISAR), Biomass, and other future sensors
Summary
Following the urgent need for improved mapping of vegetation structure (Le Toan et al, 2011) to better quantify global carbon stocks and fluxes from land use change (Houghton, 2005) and impacts on ecosystem services and forest resources (Bustamante et al, 2016), NASA and ESA have developed three spaceborne missions – NASA Global Ecosystems Dynamics Investigation (GEDI, Dubayah et al, 2020), NASA-ISRO Synthetic Aperture Radar Mission (NISAR, Rosen et al, 2016) and ESA BIOMASS (Quegan et al, 2019) - to be launched between 2018 and 2022. As a result the European Space Agency (ESA), United States National Aeronautics and Space Agency (NASA), French Aero space Lab (Office National d’Etudes et de Recherches Aerospatiales; ONERA), German Space Agency (Deutsches Zentrum für Luft-und Raumfahrt; DLR), Gabonese National Park Agency (Agence Nationale des Parcs Nationaux; ANPN), the Gabonese Earth Observation Agency (Agence Gabonaise de l’Etude et Observation Spatiale; AGEOS) and multiple international University partners collaborated on the AfriSAR campaign, to acquire coincident calibration and validation datasets that would facilitate comparison between the airborne, field and spaceborne data It follows NASA’s previous regional field campaigns, such as 1994 and 1996 Boreal Ecosystem-Atmosphere Study (BOREAS), the 2001 Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA-ECO) and the 2015 Arctic-Boreal Vulnerability Experiment (ABoVE), and ESA’s TropiSAR in combining remote-sensing techniques and groundbased experiments to assess ecosystem structure and change in re sponses to anthropogenic and environmental drivers. See the Supplemental material for a detailed description of the sites
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