The world’s biggest space-based radar will measure Earth’s forests from orbit

Forests are the second-largest carbon sink on the planet, after the oceans. To understand exactly how much carbon they trap, the European Space Agency and Airbus have built a satellite called Biomass that will use a long-prohibited band of the radio spectrum to see below the treetops around the world. It will lift off from French Guiana toward the end of April and will boast the largest space-based radar in history, though it will soon be tied in orbit by the US-India NISAR imaging satellite, due to launch later this year.

Roughly half of a tree’s dry mass is made of carbon, so getting a good measure of how much a forest weighs can tell you how much carbon dioxide it’s taken from the atmosphere. But scientists have no way of measuring that mass directly.