The Global Ecosystem Dynamics Investigation Lidar (Image Credit: NASA's Goddard Space Flight Center)

On September 8th, NASA announced the introduction of a new piece of equipment that is being developed for the International Space Station (ISS). It's known as the Global Ecosystem Dynamics Investigation (GEDI) lidar (a combination of the words "laser" and "radar") and it will use lasers to provide a unique and extremely accurate 3-D map of Earth's forests.

The instrument was selected as part of NASA's effort to study vegetation on Earth. The GEDI will help scientists study the health of Earth's forests by measuring things such as the height and density of the forest's canopy. It'll also help scientists measure how much carbon is being stored by Earth's forests. Overall, the "GEDI will provide crucial information about the impact that trees have on the amount of carbon in the atmosphere" according to the NASA press release.

Even though scientists have known for a long time that trees play an important role in the carbon cycle, the extent of that role is largely unknown. To put it bluntly, if we chopped down X number of trees in Y region, how much will it actually impact the carbon cycle? That information would be very good to know. As Ralph Dubayah, the GEDI principal investigator, said, "One of the most poorly quantified components of the carbon cycle is the net balance between forest disturbance and regrowth. GEDI will help scientists fill in this missing piece by revealing the vertical structure of the forest, which is information we really can’t get with sufficient accuracy any other way."

This is where the lidar technology comes in. Lidar allows the GEDI to measure the distance between features on Earth and the satellite. As explained by Bryan Blair, the deputy principal investgator for GEDI, "Lidar has the unique ability to peer into the tree canopy to precisely measure the height and internal structure of the forest at the fine scale required to accurately estimate their carbon content." Altogether, the GEDI will carry three lasers. This "trio of specialized lasers will use sophisticated optics to divide the three beams out into 14 tracks on the ground. Together, these tracks will be spaced 1,640 feet (500 meters) apart on the surface creating a total swath width of about 4 miles (6.5 kilometers). GEDI will sample all of the land between 50 degrees north latitude and 50 degrees south latitude this way, covering nearly all tropical and temperate forests." according to the NASA press release.

The lasers will be shot in pulses from the satellite, some of the light will reflect off the ground/biomatter and strike the satellite. The amount of time it takes the light to return will be measured and used to figure out how far away the feature is. In addition, when the laser hits the feature (whether the ground or a leaf), the frequency of the light will change a little telling scientists what (exactly) the laser came into contact with. It's estimated that GEDI will send out about 16-billion pulses a year, or about 500 pulses a second. The lasers will be completely safe to look at (actually, you wont even be able to see them), so you don't have to worry about being blinded by NASA.

Currently, GEDI is scheduled to be finished in 2018, and will likely be mounted onto the ISS shortly after that. The technology could help to revolutionize our understanding of Earth's forests.


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