Why does NASA shoot lasers at trees from the International Space Station

Why does NASA shoot lasers at trees from the International Space Station

Right now, a barrage of laser pulses is coming to Earth from the International Space Station (ISS).

Their goal is to reveal the secrets of the planet’s most private forests.

The GEDI mission, developed by NASA’s Goddard Space Flight Center and the University of Maryland, USA, enables unprecedented 3D mapping of forested areas even in remote areas.

“It’s a satellite the size of a refrigerator, it weighs about 500 kilograms and is docked or connected to one of the units of the International Space Station,” explained to BBC News Mundo, BBC’s Spanish language news service, Spanish scientist Adrián Pascual, member of the GEDI science team, mapping specialist and Forest Ecosystem Management Professor at the University of Maryland.

Mission data are essential to understanding how much forests store carbon and the impact of deforestation in combating climate change.

But is GEDI’s future uncertain? Currently, a campaign seeks to ensure the continuity of the mission.

How does GED work?

GEDI is an acronym for Global Ecosystem Dynamics Investigation.

The core of the program is an instrument that fires lasers and has been docked at the International Space Station since 2019.

The rain of laser pulses makes it possible to determine not only the height of trees, but also the structure of the forests.

Photo: NASA/Goddard Space Flight Center

“The International Space Station orbits the Earth nonstop,” Pascual explains. “Our GEDI satellite emits laser pulses all the time.”

These energy pulses make it possible to determine not only the height of trees, but also the structure of the forests.

“When the energy pulse reaches the ground, it strikes the first element it encounters, the treetops, and continues to advance until it hits the ground.”

“The sensor measures the difference between the moment the tops of trees and the ground are detected. By converting this time period into distance, we can estimate the height of vegetation.”

To reveal the composition of the forest, GEDI researchers study changes in the patterns of energy waves.

“In this way, we are able to estimate different levels of vegetation, and this gives us an idea of ​​not only the height of the forest, but also its structural complexity.”

Adrián Pascual - Adrián Pascual / Profile - Adrián Pascual / Profile

“The ability with this same tool to examine forests around the world and generate trillions of observations is really unique,” ​​says Adrián Pascual.

Photo: Adrien Pascual/Personal Archive

GEDI uses a remote detection technology called LIDAR, which basically consists of pointing a laser at a surface and measuring the time it takes to return to its source.

However, it is not a new technology.

“But this technology has never been placed on a satellite and has been flown to the International Space Station and used at an altitude of more than 400 km to specifically monitor forests,” Pascual explains.

Forest - Getty Images - Getty Images

Approximately 50% of the biomass in tree wood is carbon

Photo: Getty Images

Carbon: basic data

Trees absorb carbon dioxide, or carbon dioxide, from the atmosphere, one of the main greenhouse gases responsible for climate change.

And they store a lot of this carbon, preventing it from being released into the atmosphere.

“When trees grow, their biomass increases. And about 50% of that biomass, from the wood of these trees, is carbon,” Pascual says.

“It is estimated that a medium-sized tree, the most generalized tree imaginable, retains about 25 kg of carbon dioxide per year.”

“We’re using GEDI to figure out what the stock, and storage of carbon, is currently in all of the world’s forests.”

GEDI’s role in combating climate change

The data and maps obtained from GEDI are publicly available.

It is necessary for governments around the world to realistically know their carbon storage capacity.

Jedi - NASA - NASA

GEDI data visualization – colors represent tons of atmospheric biomass per hectare on the top map, the bottom map shows the prediction error of the GEDI biomass model

Photo: NASA

“In the case of many ecosystems, you don’t know the length of the trees or the shape of the forest,” Pascual says.

“There are areas in the Amazon and in remote places where we don’t know the height of the trees and how the biomass is distributed.”

GEDI makes it possible to detect and measure changes in biomass caused by wildfires or illegal deforestation.

The GEDI data also reinforce the importance of preserving the world’s mature forests, rather than just prioritizing new forest plantations.

Many countries include tree planting in their plans to reduce carbon dioxide emissions.

“It is true that it is necessary to plant more trees as part of solutions to combat climate change, through projects to restore degraded areas with the potential to revegetate again,” Pascual says.

However, “for many small trees to replace the carbon stored by a very large tree, it takes a lot of small trees, time, and that there are no phenomena in the meantime, such as cutting, fire, or pest attack.”

“We cannot fall into the trap of thinking that we can replace large stocks of carbon like in the Amazon, where there is a large amount of stored carbon, through farms and restoration projects.”

Moreover, the carbon stored in forests is not only above ground.

“Underneath, in tree roots, the amount of carbon can be twice what we can expect with GEDI. That’s why it’s essential to protect the planet’s ‘lungs’.”

Forest - Getty Images - Getty Images
Photo: Getty Images

GEDI Rescue Campaign

GEDI’s development and understanding of how its technology works from a space station took nearly 20 years of prior work. Many scientific studies have been conducted by researchers such as Ralph Debayeh, Principal Investigator at GEDI and Professor at the University of Maryland.

The mission is scheduled to be operational only until the end of 2023, when GEDI will be replaced by another instrument on the International Space Station.

Both researchers and government officials are currently supporting a campaign to extend GEDI’s life in space.

ISS - NASA / Goddard Space Flight Center - NASA / Goddard Space Flight Center

GEDI has been docked to the International Space Station since 2019

Photo: NASA/Goddard Space Flight Center

One of the scientists who is not part of the mission but uses its data is Flávia de Souza Mendes, a Brazilian scientist based in Germany who is part of the RSATE (Remote Sensing Application in Tropical Environment) research group.

For Mendes, GEDI plays an important role in mitigating climate change.

“Climate change will affect more people and countries from underrepresented and low-income groups. Free GEDI data can make a difference in supporting policy-making and research in low-income countries.”

On the other hand, “the carbon market is very hot right now and there are many startups that are calculating carbon stored in the forest or in reforestation and reforestation projects to sell carbon credits.”

“There is strong pressure from the international community to be able to sustain GEDI for a longer period of time,” Adrien Pascual told BBC News Mundo.

“Because every week out there, we have thousands and thousands of observations that allow us to come up with better estimates of vegetation height and biomass.”

“It’s a huge chance that we’ll be able to keep it for a few more months or years, because we really don’t know when we’ll have another opportunity like this.”

This text was originally published at https://www.bbc.com/portuguese/geral-62517387

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