4:05 AM EST, November 9, 2012
BROOKINGS - It's the greatest show about Earth, and there's no admission fee.
For 40 years, the U.S. Geological Service, working with NASA, has been streaming images of the surface of the planet through a series of six Landsat satellites. Two South Dakota State University researchers who are part of the 2012-2017 Landsat Science Team emphasized the program's importance as a critical means of documenting the Earth's surface from space.
Dennis Helder, associate dean for research from the SDSU College of Engineering, and David Roy, senior scientist at the Geographic Information Science Center for Excellence, are part of a 22-member team of nationally and internationally recognized scientists and engineers.
The Landsat Data Continuity Mission will become Landsat 8 when the satellite is launched on Feb. 11, 2013, at Vandenberg Air Force Base in California. Helder and Roy, who have been involved with Landsat science teams for the last 10 years, plan to be there.
Helder's work focuses on calibrating the images from the satellite. If we don't calibrate the images, then they are only pretty pictures, Helder said.
Calibration turns the images into data sets; each pixel measures the amount of energy welling up from the Earth. Helder tries to give scientists like Roy the most consistent data set possible.
Using that data, Roy can map the sprawl of a new housing development or look at the influence of climate over long periods on the timing of the start of spring.
I can only do that if the data the engineers give us are correct, he said.
Roy and his colleagues then convert the data into a more user-friendly format and make it accessible to everyone free of charge at http://weld.cr.usgs.gov through the NASA- funded, Web-enabled Landsat Data project. The website that began in 2010 is simply the visual interface, Roy explained. More than 100,000 Landsat images are archived in his lab.
On the website, users can find nine years of data beginning from 2003 covering the continental United States and Alaska.
Put your cursor on a point on the screen and in five minutes, you can grab the pixel values and plot the vegetation in a specific location every week for nine years, Roy said. The data can also be broken into specific seasons or months.
This wasn't always the case. Prior to 2008, scientists had to purchase these images for anywhere from $600 to $2,000 per image, and then had to manually work out the calibration and apply the algorithms necessary to extract the information.
One scene might take half a day, Roy said. Now this is all done with one click.
Making the data free means it is getting used more often and by a wider audience.
As a science team, the ball is in our court to show how valuable this data is, Helder said, and then to show the policymakers that we have to keep doing this.
Obtaining funding for each new satellite requires lobbying of government policymakers by scientists as well as all satellite data users.
In a period of time when the population has doubled and the evidence for climate change is increasing, it is so crucial that this record continues, Roy said. The only global multi-decadal baseline for change is Landsat.
Helder anticipates Landsat 8 will be the most stable instrument so far, with a signal- to-noise range 10 times better than the previous satellites, and 12-bit rather than 8-bit data-words that are music to a scientist's ears.
For the first 90 days after the launch, engineers will be busy testing the imagery. Meanwhile, these guys, Helder said, referring to Roy, will be anxious for the information.
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