Comparison of space-based technologies for measuring BIOMASS: The road to the BIOMASS mission

Information on above-ground biomass and its changes is of fundamental importance for carbon cycle and climate calculations. The difficulty of making ground-based inventories of biomass, especially in the tropics, has therefore led to serious attempts to estimate biomass from space. Active technologies hold the most promise. Lidar maps of forest height derived from IceSAT data have underpinned two recent pan-tropical biomass maps, using indirect statistical regression methods. More direct measurements of biomass are possible using radar, and can be combined with height measurements by a mission that supports a Pol-InSAR mode. Physics and experiment both indicate that the longest wavelength possible should be used, which is P-band. The BIOMASS mission is driven by these considerations, and is uniquely fitted to measure biomass, but will gain significantly from combination with both spaceborne L-band data, expected to be available during the mission lifetime, and with airborne lidar measurements.