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U.S. Satellite Images of Earth Help Countries Worldwide

U.S. Satellite Images of Earth Help Countries Worldwide

Landsat agencies committed to making data available to science community
Source: Cheryl Pellerin,, U.S. Department of State

U.S. agencies responsible for the Landsat series of Earth observation satellites have agreed that the next-generation Landsat will launch in 2011, and the United States is not the only nation that will benefit from the continued imaging of the planet’s oceans, land surfaces and ice cover.

Since 1972, a series of Landsat satellites have been orbiting Earth, collecting images from about 700 kilometers above the surface in a near-polar, sun-synchronous orbit. This means the satellite circles the planet in an almost north-south direction as Earth rotates from west to east. NASA and the Department of Interior’s U.S. Geological Survey (USGS) share responsibility for the satellites’ space and ground segments.
Landsat 5 launched in 1984 and, despite a design life of three to five years, is still operating, but with limited capability. Landsat 7 launched in 1999, and since 2003 has had a sensor problem that limits its capability. Both satellites will run out of fuel in 2010 or 2011; the next satellite, called the Landsat Data Continuity Mission, is expected to launch in 2011. (See related article.)
“The USGS and NASA are very concerned about data continuity and data access,” said Ronald Beck, USGS program information specialist for the Land Remote Sensing Program. “We’re firmly committed to finding ways to get the data into the hands of the global science community.”

Sharing Global Images

Landsat data are used in various applications, including agriculture and forestry, land use planning, water resource management, coastal zone management, ecological forecasting and disaster management.
Landsat sensors have a moderate spatial resolution. Individual houses are not visible on a Landsat image, but large objects like highways are. This is an important spatial resolution because it is coarse enough for global coverage but detailed enough to characterize human-scale processes such as urban growth.
In 2001, NASA and the USGS agreed to give the international community, through the U.N. Environment Programme (UNEP), the global Landsat dataset — satellite images of the entire planet — for 1992 and 2000.
That $20 million worth of Landsat images is allowing environment ministers in Africa, with help from UNEP, NASA, USGS, the University of Maryland and the Earth Satellite Corp., to learn about and analyze environmental changes in their regions over eight years.
Because many African countries do not have Internet access, datasets were given to ministers on high-density hard disks called “databricks” that hold hundreds of satellite images. The same data are freely accessible through Internet portals from NASA, USGS, Michigan State University and the University of Maryland.
The State Department Bureau of Oceans and International Environmental and Scientific Affairs (OES) and the U.N. Office of Outer Space Affairs held four workshops in Africa between 2003 and 2005 to review the progress made by African institutions in using the Landsat data to address sustainable development problems, said Fernando Echavarria of the Space and Advanced Technology Office in OES.
“We also worked to make sure we were making headway in getting the Landsat data out to the regional centers of excellence,” Echavarria said. “It’s a big continent and there are a lot of problems, but there’s a lot of capacity in Africa on these remote-sensing technologies.”

Tracking Health Threats

In 2000, Landsat images helped scientists from the World Health Organization (WHO), the U.S. Centers for Disease Control and Prevention, Naval Medical Research Unit-3 (NAMRU-3) and the Walter Reed Army Institute for Research deal with an outbreak — the first outside Africa — of Rift Valley fever in Saudi Arabia and Yemen.
Rift Valley fever is an acute, fever-causing viral disease that affects people and domestic animals such as cattle, buffalo, sheep and goats, and most commonly is associated with mosquito-borne epidemics during years of unusually heavy rainfall.
To support efforts by international agencies, said Assaf Anyamba, a research scientist at NASA’s Goddard Space Flight Center in Maryland, “we had to provide information for them to know where it had rained, where the vegetation had greened up. Those would be potential areas where the most creatures that carry the virus were breeding and spreading the disease.”
The scientists used a Landsat image from the period during the outbreak and compared it with an image from before the outbreak.
“We could see a big difference in terms of the vegetation greenness,” Anyamba said, “and this allowed the teams … to look at the areas along this floodplain of the Arabian-Yemen coast and respond to that outbreak.”
He added, “In areas where outbreaks occur that are small and in areas of complex topography, Landsat becomes a very useful tool for analyzing the patterns and ecological conditions.”
See also “U.S. Agencies Moving Forward in Planning Landsat 7 Successor.”
Additional information is available on the Future of Land Imaging Web site, sponsored by the Executive Office of the President.
( is produced by the International Information Programs Bureau, U.S. Department of State. Web site:

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