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April 22, 1999: Even though they deal mostly with water, scientists at the Global Hydrology and Climate Center (GHCC) are looking forward to getting data from a satellite designed to study land. "Landsat 7 is going to help us out tremendously in urban heat island studies," said Dale Quattrochi, a NASA scientist at the GHCC in Huntsville, Alabama. Quattrochi and Jeff Luvall are the GHCC's lead scientists studying urban heat island phenomenon. The central effort has been the long-term Project ATLANTA (ATlanta Land-use ANalysis: Temperature and Air-quality) which includes a University of Georgia team led by Dr. C.P. Lo. The results of Project Atlanta led to 1998's Urban Heat Island Pilot Project (UHIPP) which conducted similar measurements over Baton Rouge, Sacramento, and Salt Lake City. Right: An image from the Landsat 5 thermal channel (top)
is shows how hot areas (red) correspond with urban areas (gray)
in the false-color image of Atlanta (below). Credit: NASA and
University of Georgia On the other hand, asphalt, concrete, and other manmade materials are very effective at absorbing light and reradiating it as infrared radiation that raises the temperature of the air. In turn, that makes air-conditioning systems work harder, even after sunset. |
"Landsat 7's 15-meter-resolution black-and-white images will be very useful in combining with digital data to give us a better idea of what happens on the ground," Quattrochi said. The thermal infrared channel on Landsat 7's Enhanced Thematic Mapper will see details as small as 60 meters (188 feet) on the ground as compared to 120 meters (376 feet) with prior Landsats' thermal channels. "It's a great improvement," Luvall said. "It will give us a temporal distribution across the years and the seasons" to show trends in urban heating. The scientists still need to use aircraft, as in 1998's UHIPP, for detailed images to pinpoint individual heat sources. Aircraft are also needed to provide images to show heat storage the night immediately after a daytime observation since Landsat's orbit does not provide that sort of coverage. |
Landsat 7 will also help scientists look into the past so we can chart the future better. Left: Landsat images help reveal an ancient causeway
(faint diagonal line) and temples (white dots) at Mirador, Guatemala.
Credit: NASA |
"Already, images from earlier Landsats have helped us track the loss of rain forests to farmers and loggers," Sever said. "It has also helped us recover several archaeological sites. Landsat 7's enhanced capabilities will be of great benefit to our efforts to answer questions about the past in order to protect the resources of the future." |
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