Laser instrument to study forest health

A mockup of the Vegetation Canopy Lidar is prepared for a test shipment to the Alaska launch site.

September 24, 1999
Web posted at: 4:31 p.m. EDT (2031 GMT)

A mockup of the Vegetation Canopy Lidar is prepared for a test shipment to the Alaska launch site. A research aircraft is flying over selected regions of the U.S. this month to test a laser instrument that can map and measure the density and structure of forest vegetation. Next year, the instrument will be launched into space to make a global map of forest vegetation.

Scientists will use the maps created by the NASA/University of Maryland Vegetation Canopy Lidar to monitor the health of the forests and determine the capacity of forests to absorb carbon dioxide from the atmosphere.

They are hoping to find out whether forests and human activities in forests, such as deforestation, are acting to increase or decrease carbon in the atmosphere and thus potentially accelerate or inhibiting global warming.

"Right now it's a big guess how much carbon dioxide is put in the air from cutting down forests," said Lee Tune, a spokesperson from the University of Maryland. "The Vegetation Canopy Lidar instrument will allow for the first total inventory of how much carbon is in the world's forests."

Scientists want to know whether forests are acting to increase or decrease carbon in the atmosphere.

The instrument, which has been used to map the surface of Mars and coastal erosion on Earth, contains five lasers that send pulses of energy to the Earth's surface. Photons from the lasers bounce off leaves, branches and the ground and reflect back to the instrument.

By analyzing these returned signals, scientists receive a direct measurement of the height of the forest's leaf-covered canopy, the topography of the forest floor and the height of all the vegetation in between.

Previous satellites have mapped the location of forests in great detail, but Vegetation Canopy Lidar will be the first to map the vertical dimension of a forest. Where the leafs and twigs and branches are within a forest -- how much vegetation is high in the canopy or near the ground -- changes as a forest ages. These maps will provide a direct way to identify degraded areas, areas of regrowth and intact forests.

Scientists will also be able to calculate the above-ground biomass of a forest and, since they know about 50 percent of a forest's biomass is made up of carbon, they can estimate the amount of carbon contained in the forest.

In addition, biodiversity studies can use Vegetation Canopy Lidar's comprehensive assessment of forest structure and organization to identify and monitor important habitat areas. Vegetation Canopy Lidar Measurements of the aerodynamic roughness of forest tops will also be useful for improving weather predictions by aiding understanding of windflow over the earth.

The Vegetation Canopy Lidar is scheduled to be launched into space in September 2000 from Alaska's Kodiak Launch Complex.

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