By Patricia Daukantas
Thanks to a NASA environmental-studies satellite that uses lidar technology, scientists have produced a first-of-its-kind map of tree-canopy heights around the world. The study will help climate researchers gain new insights into the rate of carbon recycling through global forests.
According to a paper coming out in Geophysical Research Letters, Michael Lefsky of Colorado State University (U.S.A.) used lidar data taken by ICESat, part of NASA’s Earth Observing System mission, to measure the height of forest trees. The ICESat instrument known as the Geoscience Laser Altimeter System, or GLAS, measured the time-of-arrival distance between laser pulses reflected off the ground and those reflected off treetops.
Unfortunately, due to problems with its lasers, GLAS was able to perform direct sensing of only 2.4 percent of Earth’s total forest cover. Lefsky thus combined the lidar data with additional data from the imaging spectrometers aboard two other NASA satellites, Terra and Aqua.
I wrote about ICESat in my “Lidar in Space” article in the June 2009 issue of OPN. In February 2010, NASA ended ICESat’s science mission after the third and final GLAS laser failed. Last week, the U.S. space agency fired ICESat’s thrusters one more time to lower its orbit, and sometime in the next couple of months, the satellite will re-enter the atmosphere, where most of it is expected to burn up before it could reach the ground.
A second-generation laser altimeter mission, ICESat 2, is still in the early phases of development, with a launch tentatively scheduled for late 2015.
2010-07 July, Astrophysics, Miscellaneous Optics