ESA’s Biomass is the first satellite to carry a P-band synthetic aperture radar. Thanks to the long wavelength of P-band, around 70 cm, this novel radar is able to penetrate through the forest canopy, allowing it to collect information on different parts of the forest, such tree trunks, branches and stems – which is where trees store most of their carbon.

The radar is fully polarimetric, which means it is capable of transmitting and receiving in two orthogonal linear polarisations, horizontal and vertical. The different signals in each polarisation channel are needed to yield different information about the forest. However to achieve information on forest height and the structure of the forest beneath the canopy, multiple satellite passes over the exact same area are needed – a technique called synthetic aperture radar interferometry. Biomass is also the first synthetic aperture radar in space to have a dedicated tomographic phase as part of its mission plan.

The animation shows Biomass’ measuring technique in brief. A longer version of the animation is available that shows how multiple satellite passes build up key information on forests.