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A laser-based instrument was developed a few years ago by the International Space Station and will be launched at the end of 2018. It will provide a unique, high-resolution 3D view of Earth's forests, helping to fill in missing information about their role in the carbon cycle. ALSO READ: • Computer Vision: The Complete Guide!
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WHAT IS IT?
Called GEDI (Global Ecosystem Dynamics Investigation), the instrument is a geodetic-class laser system and will be the first to systematically probe the depths of forests. The system is one of two instrument proposals selected for NASA's Earth Venture Instrument program, and is being led by the University of Maryland in the US.
WHAT ARE THE ADVANTAGES of GEDI?
GEDI's precise measurements of surface elevation, forest canopy height, and vertical structure greatly enhance human capacity to characterize important carbon and water cycling processes, as well as biodiversity and habitat. “Combining ICESat-2 with GEDI, we will have a new view of the state of the biosphere on our planet,” stated Tom Neumann, assistant project scientist for ICESat-2 at NASA. GEDI data on surface structure are also of great value for weather forecasting, forest management, glacier and snowpack monitoring, and for generating more precise digital elevation models. This instrument provides exactly what was missing – 3D structure – in NASA's observational assets, allowing us to better understand how Earth behaves as a system and also guiding us regarding the actions we can take to sustain critical resources. For Ralph Dubayah, GEDI's principal investigator from the University of Maryland, this mission will answer questions about tree biomass in a given region and about the impact of deforestation and reforestation on the amount of carbon dioxide in the atmosphere. It will also quantify how the vertical arrangement of leaves and branches in a forest affects habitat quality and biodiversity.
WHAT ARE THE OBJECTIVES?
The scientific objective of GEDI is to characterize the effects of climate change and land use on ecosystem structure and dynamics to enable a radically improved quantification and understanding of Earth's carbon cycle and biodiversity. Focused on tropical and temperate forests, GEDI uses Lidar to provide the first global, high-resolution observations of forest vertical structure. The instrument addresses three fundamental scientific questions: • What is the above-ground carbon balance of the Earth's surface?
• What will be the role of the land surface in mitigating atmospheric carbon dioxide in the coming decades?
• How does ecosystem structure affect habitat quality and biodiversity?
Answering these questions is critical to understanding the future pathway of global climate change and Earth's biodiversity. While it is well established that trees absorb carbon and store it long-term, scientists have not yet quantified exactly how much carbon is contained in forests. Because of this, it is not possible to determine how much carbon would be released if a forest were destroyed, nor how emissions could be combated by planting new trees.
HOW WILL IT WORK?
The lasers will illuminate the surface with brief pulses of light, which are optimized to pass through the forest canopy – even the densest ones – without causing damage. Additionally, these lasers are eye-safe. The team estimates that the instrument will send 16 billion pulses in a year. A small fraction of each pulse (return pulse) is reflected back to a detector on the orbiting instrument. The time required to complete this round trip is precisely measured and converted into a distance. Furthermore, the materials a pulse encounters along the way slightly modify the signal, resulting in a different fingerprint or vertical profile when a pulse interacts with leafy tree canopies, woody branches and trunks, or the ground. These fingerprints will provide enough detail to measure the height of trees and to know where their canopies begin, with an accuracy of approximately one meter. With this information, scientists will be able to estimate the amount of biomass the trees contain and, consequently, how much carbon they are storing.
ADVANCEMENTS
Combining these findings with spatially comprehensive maps from other satellites, showing where development and deforestation are occurring, or with studies revealing forest composition, scientists will have a powerful set of tools to address questions about land use, habitat diversity, and climate effects. Researchers will be able to relate, for example, forest architecture to habitat quality and the biodiversity of certain birds. They will also be able to estimate the age of trees in specific forests. The ultimate goal, according to Dubayah, is to monitor these and other changes in forests over time. Citation: GEDI will be installed on the International Space Station in late 2018 and is expected to produce about 15 billion cloud-free observations during its nominal 24-month mission.
Fabio Caraça
Fábio Caraça is the Chief Growth Officer at Pix Force. He leads Pix Force's transformation into a scalable SaaS operation, combining strategic vision, culture, and high-impact execution.
