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Vegetation Canopy Lidar Mission: Possible Essay, Research Paper

Vegetation Canopy LIDAR Mission: Possible

Since the beginning of time, human activities that have been altering the Earth and its atmosphere have caused the earth to warm by about one degree Fahrenheit since the late 19th century. Whether these activities were essential or superfluous, the effects on and surrounding Earth are multitudinous. For example, a warmer Earth could lead to the spread of diseases, melting polar ice caps, receding glaciers, and a change in precipitation patterns (Gay 21). Recently, scientists have concluded that this shift of climate due to the buildup of greenhouse gases, in part, might be accredited to the popular practice of deforestation. Because human activities have altered the chemical composition of the atmosphere, scientists have developed laser-based sensors to map the structure of vegetation in the world’s forests.

Some naturally occurring greenhouse gases such as water vapor, carbon dioxide, methane, nitrous oxide, and ozone are released into the atmosphere through the normal methods of burning fuel and transporting coal (McCuen 15). Certain human activities add to the levels of these naturally occurring gases. Greenhouse gases that are not naturally occurring are called chlorofluorocarbon, hydroflurocarbons, and perfluorocarbons. These are generated by industrial processes (“Global Warming” 1). Scientists believe that deforestation is a major contributor acting to increase or decrease carbon into the atmosphere, in turn, potentially accelerating or inhibiting global warming. To date, scientists can only postulate how much carbon dioxide is being emitted into the air from the cutting down of forests. Therefore, scientists have developed a laser-based sensor to determine this mystery.

Ground based LIDAR systems were introduced in the early 1960s, and were used to monitor the ozone and upper atmosphere. Then in the 1970s, airborne LIDAR devices were developed to extend local views to regional scales (Roach 2). The first space-borne LIDAR, which provided the first detailed global profiles of the multi-layered structure of clouds, flew aboard NASA’s space shuttle in 1994. Today, the Vegetation Canopy LIDAR Mission, led by Dr. Ralph Dubayah of the University of Maryland, will be the first launching of a light detection and ranging (LIDAR) device on a satellite to provide scientists with a look at Earth’s environment. This launching will be known as the Vegetation Canopy LIDAR Mission (Isbell 1). The Vegetation Canopy LIDAR Mission will allow scientists to assess a total inventory of how much carbon is in the world’s forests (Higgins and Roach 1). Obtaining an inventory of the vertical structure of forests across Earth’s surface is possible because the Vegetation Canopy LIDAR Mission will map in three dimensional format the “direct measurement of tree heights, forest canopy structure, and derived parameters such as global biomass with at least ten times better accuracy than existing assessments” (Isbell 1). Such information will provide an update of global forest health as well as produce an approximate count of how much carbon the forests hold. Knowing how much carbon Earth’s forests hold is a key factor in climate change economics (Roach 1). At this point, scientists are able to calculate the above-ground biomass of a forest and they know that about fifty percent of a forest’s biomass is made up of carbon. With the information from the Vegetation Canopy LIDAR Mission, they can estimate the amount of carbon contained in the forests (Higgins and Roach 2). These maps will also help scientists identify degraded areas in the forests. Because of cloud cover, many important ecosystem properties of the vegetation and surface of moisture conditions of the forests can not be adequately assessed (Waring 715). The Vegetation Canopy LIDAR Mission has the ability and accuracy to pierce cloud cover which will solve this problem. Most instruments used by scientists to observe Earth can not project through the thinnest of clouds without producing a distorted image (Roach 1). In addition, bio-diversity studies can use the Vegetation Canopy LIDAR Mission’s comprehensive assessments of a forest’s structure to identify and monitor habitat areas. The Vegetation Canopy LIDAR Mission will also aide in the prediction of weather patterns because the measurements it can take help in the understanding of wind flow over the earth.

The Vegetation Canopy LIDAR Mission will use five lasers that send pulses of energy to the Earth’s surface. Photons from the lasers bounce off leaves, branches, and the ground then reflect back to the instrument. The Light Detection and Ranging (LIDAR) device is the same type of device as the Radio Detection and Ranging (RADAR), but the energy sources are different. LIDAR devices are active remote sensors since they include the light source (Cross 1). The Vegetation Canopy LIDAR Mission uses pulsed radar from a single-instrument, a small spacecraft, 400 kilometer altitude, global remote sensing of tree canopy height, vertical distribution of intercepted surfaces in the canopy, and ground topography. The LIDAR instrument for the Vegetation Canopy LIDAR Mission is the Multi-Beam Laser Altimeter (MBLA). This device has five laser transmitters, a large receiver telescope, a set of five detectors and laser-pulse analysis electronics, computer data electronics, and a pointing angle measuring system. “The primary role for MBLA in measurement of the Earth’s vegetation canopy is enabled by the related techniques of laser pulse time-of-flight measurement and laser pulse shape analysis that constitute a LIDAR capability for remote sensing of the Earth’s surface” (Doherty 1). The laser-based sensors (LIDAR) operate in basically the same manner as RADAR. The Vegetation Canopy LIDAR will fire out pulses of laser radiation and the LIDAR collects the photons with optical telescopes (Roach 2). By analyzing the returned signals, scientists receive a direct measurement of all the information the devices offer (Higgins and Roach 2).

The Vegetation Canopy LIDAR Mission is scheduled to be launched into space in September 2000. It will ascend from Alaska’s Kodiak Launch Complex (Higgins and Roach 3). NASA and the University of Maryland are working together to plan other launchings of laser-based satellites into orbit. In July 2001, a laser instrument will ride aboard a satellite to map the surface of Earth’s ice sheets. This mission will produce results with a vertical resolution of just four inches. A comparison of this new data over several years will enable scientists to calculate the amount of ice that has been lost due to global warming and has contributed to a rise in sea levels. In the year 2003, scientists are planning to implement laser-based sensors on a mission to measure the chemical composition and structure of clouds to improve climate forecasts (Roach 2). These exciting and innovative missions will deliver their first science results in a little over three years. Not only are these exciting and innovative missions capable of producing fast results, but also they are cost-effective for NASA’s budget. These missions will provide the answers to “emerging research questions that will further expand the scientific knowledge of the Earth” (Isbell 1).

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