Photo: NASA

Measuring the world’s forests from space

Wednesday 12 Dec 18

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John Leif Jørgensen
Professor and Head of Measurement and Instrumentation
DTU Space
+45 45 25 34 48
NASA has now initiated a new space mission to measure Earth’s forests and other biomass with razor-sharp precision through the help of DTU Space.

The purpose of the mission is to gain an extremely detailed overview of the impact of vegetation on the CO2 balance and climate of Earth.

On Wednesday, 5 December, The Global Ecosystem Dynamics Investigation (GEDI) was sent into space towards the international space station, ISS. GEDI is a climate mission and a remarkable instrument, which will be mounted on the space station.

From space, it will measure the height and extent of forests and other biomass on Earth in 3D through the help of a laser, and will thus ensure new important knowledge about how Earth’s ecosystem absorbs and releases CO2.

“This is a huge task. Enormous amounts of data will come from this eco-laser mission,” says Professor John Leif Jørgensen, DTU Space, who is in charge of DTU’s contribution to the mission.

"In principle, you will actually be able to see how fast each individual tree is growing."
Professor Jørgensen, DTU Space

“We will measure all biomass on Earth, so, in principle, you will actually be able to see how fast each individual tree is growing.”

DTU Space has developed three stellar cameras and the software to control them, which will help to ensure the correct position of the GEDI instruments when pointed at Earth. Among other things, this will ensure that the precise orientation and position of the laser instrument when it scans Earth is known. In this way, the collected data can subsequently be precisely linked to a given position on Earth.

3D scan of Earth’s surface
GEDI’ equipment scans biomass on the surface of Earth in 3D. This is done many times, allowing the researchers to keep track of the current biomass and how it changes over time.

“This mission enables us to investigate and gain a better overview of how drought, air flow, temperature, and water conditions impact the CO2 absorption and release of Earth’s ecosystem. Such a global overview is not available today,” says John Leif Jørgensen.

Researchers from DTU also expect to work with the readings from the GEDI mission, which, in addition to NASA, also involves the University of Maryland in the US.

Extremely powerful laser
The precision measurements become possible by means of an extremely powerful laser that sends light towards Earth and picks up the signal as it bounces back.

By analysing differences in the light emitted from and received by the GEDI laser, the extent of trees and biomass is determined. The laser “sweeps” back and forth on Earth from the ISS, as it travels along its orbital path, orbiting Earth 16 times a day.

The expected duration of the mission is two years. Thus, a very large number of readings and a very extensive coverage of Earth are achieved.

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