2002 EARTH SCIENCE VIDEOTAPES |
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Tape Title | Record ID | Date Produced | TRT: |
Synopsis |
| LASERS ON ICE: ICESAT BEGINS ITS MISSION | G02-085 | 11/27/02 | 00:50:41 |
Frozen does not mean immobile. To scientists who study the nature of our home planet's climate, the frozen poles of Earth are dynamic and dramatic places. That's why NASA is sending a specialized spacecraft into orbit, specifically tailored to study changes in global ice cover. Called ICESat, for the Ice, Cloud and land Elevation Satellite, it will use a technology called "lidar" to map the Earth. It's a high tech, yet proven system that's been used with great success in mapping Mars. By using lasers to literally measure changes in planetary features, the space agency will collect critical data about our home.
Although principally designed to measure changes in global ice cover, ICESat will also make important readings about clouds, atmospheric aerosols, vegetation, land topography, and the oceans.
CREDIT: NASA
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TAPE CONTENTS: |
| ITEM (1) Reporter Package: Speed of Light - Speed of light.
It's a universal constant.
It's absolute.
Take a beam of light… bounce it off an object…measure the amount of time it takes to come back. What you get…is a measure of distance. That's the purpose of ICESat's one scientific instrument. A beam of laser light from space bounces off the Earth's surface forty times a second. Since experts will know the precise altitude of the spacecraft at all times, they'll be able to use the laser data as a rangefinder to determine surface elevations to an accuracy of roughly six inches. Viewed collectively, these measurements will add up to remarkably detailed elevation maps of the planet's surface.
SOT - Dr. Jim Watzin, ICESat Project Manager
It's important science. The global climate and what the cycles are in the Earth's climate and whether man is influencing it, whether today's environment is influencing it is a question of importance to all of us.
As its name implies, ICESat will focus on Earth's frozen reaches, also known as the cryosphere. While the North Pole is entirely devoid of land, with a skin of ice floating on a frigid ocean, the South Pole is a continent covered by ice up to two miles thick. By studying these dramatically different environments, plus the dynamically variable surface of Greenland, experts are planning on new insights into how the Earth's overall ice inventory is changing, and thus affecting sea levels.
But the study of polar ice sheets is only the beginning. A laser in space affords scientists a powerful tool for several other important research pursuits.
SOT - Dr. Jay Zwally, ICESat Project Scientist
It's actually a multi-disciplinary mission. The primary purpose of Icesat is for measuring the ice sheets. That's basically why the mission is there. But the "C" stands for clouds and the "E" stands for elevation-for land elevation and trees.
The technique is called laser altimetry, and NASA helped write the book. Using a similar system, experts refined space based laser altimetry around our planetary sibling Mars. The Mars Orbiting Laser Altimeter flying onboard the Mars Global Surveyor spacecraft captured surface details about the Red planet that had never been seen before. In fact, we currently have a better picture of Martian topography than we have of our own planet Earth. But considering that the laser technology on ICESat is more than 10 times as accurate as that orbiting Mars, this new Earth Observing mission is set to revise the score.
Climatological balance depends on a complex interplay of the atmosphere, oceans, and land. With shifting worldwide climate conditions more and more a focus of international consideration, the ICESat mission assumes an important role in the space agency's growing Earth Observing System fleet.
CREDIT: NASA
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| ITEM (2) VO - Looking Down With Lasers - How cool is this? An orbiting observatory… precisely measuring changes in total ice covering Greenland and Antarctica…enabling researchers to monitor how those changes affect overall sea levels…measuring the height of Earth's vegetation canopy while analyzing details about global cloud cover. Very cool--which is why NASA's launch of the ICESat research satellite has scientists all heated up.
The satellite uses lasers as ultra-precise orbiting tape measures, plotting changes in a variety of features about the planet below. ICESat fills an important slot in the space agency's Earth Science Enterprise and its growing Earth Observing System fleet.
CREDIT: NASA
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| ITEM (3) ICESat: Laser Light Measures Earth's Ice - The satellite is called ICESat; the scientific instrument it carries is called GLAS, the Geoscience Laser Altimeter System. Experts designed the GLAS instrument principally to measure changes in the overall surface elevation of the polar ice sheets through time. The system will also make important measurements about clouds, from cloud height to cloud structure. It will also help researchers measure land surface topography, as well as make determinations about surface feature characteristics, including reflectivity, vegetation heights, as well as snow and sea-ice surfaces.
CREDIT: NASA
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| ITEM (4) Near-Polar Orbit, Worldwide Measurements - The ICESat satellite left Earth from the Vandenburg Air Force Base in California. It rode into orbit onboard a Boeing Delta II rocket, model 7320. Manufactured by Ball Aerospace, the ICESat spacecraft will initially fly at 367 miles (590 km) above the Earth. It's designed to operate for a minimum of three years, delivering data to Earth-bound scientists every day.
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| ITEM (5) Through The Looking GLAS - GLAS-the Geoscience Laser Altimeter System-is the only scientific instrument aboard Ice, Cloud and land Elevation Satellite. The large cylindrical side of the satellite comprises the biggest part of the GLAS instrument. It's the one-meter observatory mirror, the part of the instrument that detects reflected pulses of laser light from the Earth below. Beside that large mirror is a small "tunnel": that's the laser emitter. The onboard laser will emit short pulses of light forty times a second in two different wavelengths towards the Earth. By the time the laser pulses reach the surface of the planet, they will have spread out to "footprints" roughly 70 meters in diameter, with roughly 170 meters of space between each subsequent pulse along the ground track.
CREDIT: NASA
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| ITEM (6) Accumulating Data:
Glas Builds Its Facts One Point at a Time - The technology behind GLAS is called lidar. Lidar is a distance measuring system similar to radar, except that instead of radio waves it uses pulses of laser light for range finding. The name is a contraction based on the words light and radar: LIght Detection And Ranging. A lidar system determines precise distances by measuring the amount of time necessary for a pulse of light to leave an emitter, hit a target, and return. In this case, distance measurements helped researchers determine changes in ice thickness, vegetation, cloud thickness, and much more.
CREDIT: NASA
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| ITEM (7) Light Through the Clouds - Laser light emitted by the GLAS instrument will do more than provide measurements about the surface of the planet. One of the other important topics of investigation will be cloud cover. By passing GLAS's laser light through clouds, scientists will be able to make precise and vital measurements about cloud heights and structures-important details for determining important trends in the planet's overall climate system.
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| ITEM (8) Green Mansions:
ICESat and the Vegetation Canopy - Using the GLAS instrument, ICESat will also be used to study changes in the height of vegetation around the world. The process for doing this is clever. The instrument laser fires in pulses. By separating the partial reflection of the vegetation canopy from the basic structure of the surrounding plant life and ground surface, vegetation height can be determined. Further, by comparing the relative reflectivity of the two wavelengths emitted by the laser, experts can develop a vegetation index that's independent of other measurements based on observations of reflected sunlight.
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| ITEM (9) Changing Seasons, Changes in the Ice - Research and data collection of Arctic Ocean ice isn't easy. But using data collected by a number of different satellites from 1990 to 1999, scientists have been able to stitch together a quality-controlled record of sea ice in that part of the world. In this sequence we can see how ice around the poles oscillates seasonally. The data used to create these images come from different instruments onboard a collection of meteorological satellites. In spring and summer, the ice shrinks, and in autumn and winter it grows. Scientists use observations of seasonal changes in the ice to determine if biannual averages are changing over time.
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| ITEM (10) Greenland's Thinning Ice (G00-068) - Based on recent research using NASA's airborne laser altimeter, scientists have identified pronounced thinning of Greenland's ice cap. In the following animation, blues indicate areas where the loss of ice is greatest, and yellows indicate regions that are apparently thickening. Gray areas indicate no significant change in ice thickness there. Notice how the thinning is most severe at the coasts. As ice melts near the edges, it gives up moisture to the slightly warmer air around it. That air rises to higher altitudes inland and the moisture precipitates out as snow, increasing inland elevations. Thus, a slight thickening in the interior supports observations of a greater net loss to the overall sum of Greenland's ice cap.
CREDIT: NASA
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| ITEM (11) Lidar: Using Light to Measure Height (G00-068) - Lidar is a distance measuring system similar to radar, except that instead of radio waves it uses pulses of laser light for range finding. Lidar derives from the words light and radar. The instrument determines precise distances by measuring the amount of time necessary for a pulse of light to leave an emitter, hit a target, and return. In this case, distance measurements helped researchers determine changes in ice thickness.
CREDIT: NASA
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| ITEM (12) Crisscrossing Greenland by Plane (G00-068) - Initial research into Greenland's ice cap using lidar began in 1993 when a team from NASA's Wallops Island Flight Facility surveyed the area. Flying an aging but sturdy aircraft called a P-3B, altitude measurements were taken again in 1998 and 1999 for comparison. Researchers could essentially duplicate airplane flight paths due to a highly precise Global Positioning System (GPS) flown onboard..
CREDIT: NASA
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| ITEM (13) Lidar: Measuring Terrain on Earth and Elsewhere (G00-068) - Lidar offers diverse scientific disciplines powerful tools for exploration. Besides being used to study Greenland's ice cap, lidar has been used to study coastal erosion on both the east and west coast. Additionally, a lidar system managed by the Goddard Space Flight Center is currently orbiting Mars as part of the Mars Global Surveyor spacecraft, engaged in a detailed mapping project of the red planet.
CREDIT: NASA
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| ITEM (14) Ice: The Planet's Thermostat - Here we begin with a view of Greenland as it may have looked 100,000 years ago. Moving in, notice what happens as the climate begins to warm. Glaciers surrounding the edge of Greenland begin to slump, then melt, adding billions of gallons to the oceans. The humid air from the coasts rises to the interior, where it cools and dumps snow. When the camera pulls back, we see Greenland's ice cap much reduced in size, resulting in measurable and significant changes to the world's climate.
CREDIT: NASA
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| ITEM (15) Streams of Ice (G99-135) - Recent observations by a NASA-launched Canadian spacecraft called Radarsat are giving scientists a remarkable view of two fascinating features of Antarctica's landscape. Over a twenty-four day span, scientists used two images over identical regions of Antarctica in a technique called interferometry. Their comparative analysis of the images helped develop the following ice stream animations on the west side of the continent, showing flow rate and direction to an extent never before possible.
CREDIT: NASA
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| ITEM (16) Vector Analysis of Flow (G99-135) - In this visualization, longer black lines indicate a faster rate of flow than shorter lines. The fastest ice streams can move 400 to 500 meters a year, a blazing speed compared to tributary speeds of little more than 10 meters a year. Experts say the new information can help describe large scale changes to the Antarctic environment, as well as historical models about geological change.
CREDIT: NASA
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| ITEM (17) How They Work: A Virtual Model of Ice Streams (G99-135) - Experts still aren't positive how ice streams actually work. The current theory says that tributaries of slower ice come together to
create larger streams, often at points where elevation and terrain merge and act like a sluice. At these convergences, ice then literally slides across a lubricated bed of oceanic muck covered by a millimeter thin layer of water, gaining strength as it drives toward the ocean.
CREDIT: NASA
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| ITEM (18): Bright White Reflects Light (G00-016) - The polar caps not only hold much of the planet's total fresh water, but also play an important role in regulating the Earth's temperature. The relevant characteristic is called albedo. It's a measure of how much radiation, or light, is reflected from a body. Similar to how a white shirt helps keep a person cooler in the summer than a black shirt, the vast stretches of polar ice covering much of the planet's top and bottom reflect large amounts of solar radiation falling on the planet's surface. Were the ice caps to appreciably recede, sunlight that otherwise would have been reflected back into space would get absorbed by the darker, denser mass of ocean and land beneath. As light is absorbed, the environment is heated, thus intensifying a feedback loop: a warmer planet yields more ice melting thus an even warmer planet.
CREDIT: NASA
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| ITEM (19): Is the Ocean Rising? (G99-080) - This animation provides a more close-up perspective of the relationship between ice and solar reflectivity. As glaciers, the polar caps, and in this case, icebergs melt, less sunlight gets reflected into space. It is instead absorbed into the oceans and land, thus raising the overall temperature, and adding energy to a vicious circle. Of the many concerns voiced by scientists who study global warming trends, rising ocean levels is one of the most dramatic.
CREDIT: NASA
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| ITEM (20): RADARSAT:
International Collaboration Reveals a Continent - In the following collection of images, we look at various regions of Antarctica, the southernmost continent. The satellite that collected the data for each of these scenes is called Radarsat, a Canadian spacecraft placed on orbit by NASA.
CREDIT: NASA
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| ITEM (21) Antarctica Tour:
Ross Island/McMurdo Station (G99-080) - Ross Island is home to McMurdo Station, the largest permanent facility on the continent. Owned by the United States, McMurdo Station and its attendant airport called Williams Field are primary gateways to the rest of the frozen territory of Antarctica. Nearly 1200 researchers and support staff live at McMurdo during the summer months; about 230 remain year round. The high point of Ross Island is Mt. Erebus, rising 3794 meters. It's also the most active volcano on the continent and one of the active volcanic vents that's responsible for the formation of the island. Many days of the year a plume can be seen emanating from the mountain's summit crater, which holds a unique lava lake.
CREDIT: NASA
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| ITEM (22) McMurdo Dry Valleys (G99-080) - These valleys found at the eastern edge of the Transantarctic Mountains are essentially snow free. Melt water from alpine glaciers essentially run into these valleys and feed a number of lakes and small ponds, but otherwise, it gets very little moisture. It's a delicate environment. But its relative protection from the harsher surrounding features of the mountains and East Antarctic Ice Sheet also provides a unique opportunity for intense study. The National Science Foundation maintains a long term ecological research site in the McMurdo Dry Valleys to study the area and ecosystem.
The area is also something of a practice facility. The cold, arid conditions provide a fairly good simulation of the surface of Mars. NASA engineers have used the Dry Valleys to test equipment and operational techniques in preparation for a chance to try their designs on the Red Planet.
CREDIT: NASA
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| ITEM (23) Allen Hills (G99-080) - Along the edge of the Transantarctic Mountains lay the Allen Hills. Ice pushes up against the slopes of the hills, nudging bits of debris and surface material along. There against the slopes that ice ablates rather quickly-it's worn away-by wind and solar insolation. Left behind, however, are the geological artifacts that most interest scientists, including fragments of meteorites. It is from the Allen Hills that several years ago scientists found a fragment of something they believe is an actual piece of Earth's second closest neighbor: Mars.
CREDIT: NASA
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| ITEM (24) Amundsen-Scott South Pole Station - The U.S. National Science Foundation (NSF) operates the Amundsen-Scott South Pole Station, but it's been a way station for researchers from around the world. Seen from Radarsat, the main geodesic dome is visible along with several storage facilities. Extending to the upper right from the research station is a long line. It's a highway of sorts, heading to a now abandoned antenna facility. The bright band below the main station is the airfield for the facility 14,000 feet long.
CREDIT: NASA
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| ITEM (25) East Antarctic Ice Streams / West Antarctic Ice Streams (G99-080) - Antarctic ice streams are actually enormous glaciers, stretching like conveyors of cracked ice and snow across vast stretches of the continent. The Recovery Glacier, one of the principal channels comprising the East Antarctic Ice Streams, reaches over 800 kilometers into the continent's interior. The West Antarctic Ice Streams are to Antarctica what a fast eddy is to an already dynamic river. Moving roughly 500 meters a year-significantly faster than a typical glacier-the ice streams are hundreds of kilometers long and up to fifty kilometers wide. By comparison, the frozen material lining these remarkable rivers may move only a couple of dozen meters a year. Experts are still not positive about why they move so quickly; unlike water rushing down a trough there isn't much of a slope to pull them. Theories include a lubricated stream bed of some sort, helping the ice rush across the frozen continent like waxed sled runners in a groove.
CREDIT: NASA
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| ITEM (26) Snowdunes Ripple Antarctica's Surface (G99-080) - These snow dunes are believed to be highly stable surface features. They're made of ice particles, or grains, of different sizes. Individually each dune is nearly impossible to see without the aid of satellite remote sensing systems, but the range of the snowdunes is larger in total area than the state of California. Stretching for hundreds of kilometers, these dunes rise only 2 to 3 meters but often have a periodicity of more than 2 kilometers; that means there may be as much as 2 kilometers between each dune possible.
CREDIT: NASA
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| ITEM (27) Lake Vostok (G99-080) - More than two miles beneath the icy cloak shielding Antarctica from the sky hides a massive fresh water lake. Seen from Radarsat, the lake appears as a flat plain surrounded by the sandpaper of craggy ice. As the topographical ice sheet flows over the subglacial lake, surface features smooth out. Researchers are considering a drilling mission to the lake for exploration of this remote environment. It remains in liquid state partially due to geothermal heating and partially because of the insulating properties of such a thick ice blanket above. The drilling project faces certain technological challenges. Major mechanical work is always difficult in the bitter cold. But from a more research oriented perspective, there's the issue of how to drill into the lake from above without contaminating a sample from below with the drilling apparatus.
CREDIT: NASA
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| ITEM (28) Larsen Ice Shelf (G99-080) - In 1978, scientists predicted that global warming would lead to a disintegration of Antarctic Peninsula ice shelves. Spaceborne data indicate that this prediction may be coming true. In these before and after images, note the dramatic change in the apparent shoreline. Scientists captured the first image in using the ERS-1 satellite in 1992. As seen in the second image, collected by Radarsat in 1997, huge changes have come to the coastline. In 1995, a 2000 sq. kilometer section of the ice shelf collapsed into thousands of fragments that eventually drifted out to sea. Researchers are still debating why the ice shelf broke up so dramatically, and what significance the break up has for interpreting local versus global changes to the environment. Theories include a series of warmer than usual summers that may have caused high levels of surface melting, or an overall climate warming trend.
CREDIT: NASA
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| ITEM (29) Fimbul Ice Shelf (G99-080) - Icebergs form when hunks of ice break away from glaciers pushing into the ocean. Ice shelves are the edges of those glaciers, extending out into the ocean faster than ice bergs can break off from the edge. The Fimbul Ice Shelf has remained relatively consistent in its appearance for the last thirty years, but researchers are paying close attention to changes. Ice shelves are considered to be particularly sensitive to climatic changes and scientists have detected a marked retreat of several along the Antarctic Peninsula. Note the fascinating formations along the Fimbul, believed to be the product of glacial ice flowing over rocky outcroppings and islands.
CREDIT: NASA
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| ITEM (30) Lambert Glacier (G99-080) - Covering more than a million square kilometers, Lambert Glacier is one of the world's longest and largest. It's more than 400 kilometers long, emptying a significant portion of East Antarctica into the Amery Ice Shelf. Much like a major river system, Lambert Glacier is fed by a complex series of tributaries.
CREDIT: NASA
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| ITEM (31) Amery Ice Shelf (G99-080) - The Amery Ice Shelf spreads from the mouth of the Lambert Glacier. For the most part, ice shelves grow from glaciers pushing down into the sea. To a lesser extent they also grow from precipitation. Ice Shelves respond to climate change faster than sheets of ice on the ground or continental glaciers. Continued study of ice shelves like Amery are intended to help scientists better understand what sorts of changes are happening to the world's climate in general. Of particular interest is whether observed changes in various ice shelves are the result of natural processes or are anthropogenic, that is, the result of actions taken by humans.
CREDIT: NASA
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| ITEM (32) Ronne Ice Shelf (G99-080) - The Ronne Ice Shelf grows primarily due to a constant flow from inland ice sheets. Where shearing stresses are greater than the strength of the ice itself, cracks form. These cracks ultimately widen and spread like varicose veins in the frozen skin of the coast, only to break loose and become icebergs. Early in the 1990's a slab of ice the size of Delaware broke free from this area. Interestingly, as ice shelves break up into icebergs, overall sea level generally doesn't rise. That's because ice shelf are ostensibly already floating in the water. Floating ice shelves, connected to the shore by ice sheets and glaciers, displaces a volume of water equal to the volume of water contained in the shelf. When a berg breaks off, or calves, there is no new water to displace. It simply separates from shore...and goes on its way.
CREDIT: NASA
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| ITEM (33) Selected Soundbites With Dr. Jim Watzin, ICESat Project Manager and Dr. Jay Zwally, ICESat Project Scientist
CREDIT: NASA
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Earth Science Gallery