Yes, the future of the world’s climate is tied to the ability of forests to absorb atmospheric carbon. But exactly how well they can do that job depends on the density of the forests themselves, and scientists don’t have exact measures of that—yet. Soon they’ll have a new way to obtain that information from 268 miles above the earth.

The Global Ecosystem Dynamics Investigation (GEDI) is a lidar, or laser-based, instrument being developed for the International Space Station. Once installed, in 2018, the $94 million device will beam three infrared lasers at earth, 240 times per second, or 16 billion times per year. Those light pulses will hit the forest floor and canopy, and the time that the reflections take to reach the space station will indicate the height of the trees. Three-D maps based on that information will lead to new estimates of forest biomass and, hence, the appetite for atmospheric carbon dioxide, consumed during photosynthesis.

While satellite sensors have been collecting forest data for decades, none has been as precise as GEDI will be. To be sure, the space station’s orbit will enable the lidar instrument to collect data only on forests between the latitudes of 50 degrees north and south, roughly from the U.S.-Canada border to the bottom of Argentina. That skips Canada’s immense boreal forests and much of Russia, but does include the forests of the Amazon and Africa. The project director, Ralph Dubayah of the University of Maryland, says ecologists “have waited almost 20 years to have measurements like this.”