By Luke Gentile
In December, a new Global Ecosystem Dynamics Investigation (GEDI) instrument developed by a UMD professor will launch from the Kennedy Space Station to help scientists understand man’s impact on atmospheric carbon dioxide concentrations.
Ralph Dubayah, a professor of geographical sciences at UMD, is the project’s principal investigator and said the main focus of GEDI is to capture how tall trees are globally.
“Taller trees weigh more than shorter trees, and that is called their biomass,” Dubayah said. “So, if you cut them down and weigh them, half of that tree’s weight can make it up into the atmosphere as carbon dioxide.”
Dubayah said globally, there is no good picture of the carbon content of the earth’s forests, making it difficult to understand the impact of deforestation on atmospheric CO2 concentrations.
“There are two missing pieces of the carbon cycle,” he said. “One is what happens when you cut the trees down, how much carbon do they release. The second missing piece is, when we have young rapidly growing trees, how much carbon do they take out of the atmosphere? We don’t know the balance between deforestation and regrowth, and that is the biggest uncertainty in the carbon cycle.”
GEDI will use light detection and ranging (LIDAR) to answer the questions of the carbon cycle.
LIDAR works by shooting a pulse of laser or energy toward a surface and starting a timer. The pulse hits something, reflects off its surface and comes back. The timer is stopped, and scientists are able to see how long it took the light to travel from the sensor and come back. Researchers, knowing the speed of light, simply divide the time of travel by two to find out how far away something is.
“As I shoot this pulse of energy toward a tree, and it hits the top of the tree, some of the energy comes back, but more of the energy goes through the tree and it reflects off the leaves and branches before hitting the ground,” Dubayah said. “The last big return on the waveform is where the ground is, and I can see where I got the first return, where the energy started coming back. So, what I get is a kind of three-dimensional view of the canopy.”
Jack Pfeiffer, a junior geography major, said GEDI is another example of how using lasers provides much more information than conventional mapping.
“Mapping isn’t about just finding solutions; it’s more about analysis. We take the data, analyze the data and then pass it on,” he said. “Lasers are able to gauge things that can’t be gleaned simply from a photograph. You can shoot a laser into a body of water and take its temperature and depth, getting that specific data.”
Pfeiffer was also impressed to see that Dubayah’s instrument was selected as a competitive joint NASA mission.
“The fact that UMD got selected for this shows UMD has a strong tie to NASA, with the Goddard Space Center being right down the road, and I can only assume it’s pushing the envelope. From what I read, it sounds like we are doing some pretty crucial work,” he said.
Dubayah explained that NASA holds competitions where institutions, individuals and companies can propose space missions.
“This is called the Earth Ventures Program out of NASA, and I put together a proposal with NASA Goddard to build this instrument for that competition,” the researcher said. “I think there were about 26 other missions that were proposed, and we were selected.”
With a price tag of $94 million, Dubayah called the project’s cost a bargain.
He said, “The costs essentially go to build the instrument. It has three lasers, a lot of electronics, three star trackers, a high-end GPS and a one meter beryllium mirror. Then there is money for the science team to take and distribute the data sets.”
Both Dubayah and Pfeiffer said the findings of GEDI will surely make it back into the classrooms and curriculum of UMD students.
“I would love to get more hands-on with LIDAR technology and use that to gather more practical and useful data,” Pfeiffer said.
Dubayah said GEDI will be a once-in-a-lifetime opportunity for a university instrument to provide data for students at the institute to go look at and analyze.
“It is pretty exciting to have, in real time, an instrument that the University of Maryland has created beaming data down from the ISS. We would leverage that and include it in our courses on remote sensors. Also, there are opportunities, if you are an engineering student, to participate in how the mission is run.”
According to GEDI’s website, the instrument is currently held at the Kennedy Space Center, and a launch to the International Space Station (ISS) is expected in less than two months via a Dragon Capsule on SpaceX 16.
Photo courtesy of GEDI website: https://gedi.umd.edu