U.S. Earth observation satellites are tracking fires around the world, changing the practice of wildfire management. A group of orbiters offers an unparalleled view available only from space.

Over the past few years, the U.S. space agency NASA has launched a sophisticated pair of satellites to observe many aspects of Earth's environment. The job of the instruments on board includes detecting wildfires anywhere on the planet around the clock.

The two spacecraft are flying in formation, one behind the other over the poles, separated only by minutes. Senior NASA scientist Vince Salamonson says their combined sensors provide an up-to-date, almost instantaneous overview of where fires burn and how they change, even blazes as small as a fraction of a hectare.

"So we're seeing the big picture as well as the local picture," he explained. "We can zoom in so you can see the fire, where it's hot, how much it has burned, and then we can take a look at the height of the plume of smoke that's coming from the fires and see how far the pollution extends."

Another use for the monitoring is compiling a global record of fires. University of Maryland geographer Chris Justice, who assesses the data, says the U.S. satellites are watching infernos on many continents.

"We have fires in Africa. You'll see fires in the forests of Siberia in Russia, fires in Southeast Asia. We have extensive fires in Argentina, parts of Brazil, and of course our own fires out West," he said. "This really is a fire planet and any time of the year there is a fire season burning somewhere."

Mr. Justice says fires occur because of changing weather patterns, drought, and changing land use, such as clearing for farmland. The expansion of housing in fire-prone areas is also increasing risk.

In one example of cooperation in global fire management, Mr. Justice says the U.S. satellites have provided Russian fire agencies with images of the blazes in Siberia, where over 600,000 hectares have burned this year.

The manager of remote sensing for the U.S. Agriculture Department's forest service, Tom Bobbe, says the key to containing a blaze is the immediacy of the data.

"What's important is that the information is accurate and it's timely," he said. "Yesterday's fire map has very little value to a fire manager who is making a decision today."

NASA says that when a fire is raging, data from satellite overpasses are fed into computer models that are updated four times a day.

Mr. Bobbe stresses that each of the U.S. observation satellites has unique instruments that sense different phases of a fire. Information about a region is assessed even before a fire begins and continues long after it is out.

"The first phase is to help with vegetation mapping and the assessment of fire risk," he said. "Chris already mentioned the act of fire mapping, which provides a national-scale look at where wild land fires are burning. Following a fire, we are faced with the challenges of providing rehabilitation for those burned areas."

The imagery can help classify the severity of the burn to let fire managers prioritize recovery work. It can also track the progress of replanting burned areas and monitor the effectiveness of various treatments.

Beyond the impact fires have on terrain, scientists also study their effect on the atmosphere. The University of Maryland's Chris Justice points out the questions include how it relates to the Earth's protective ozone layer, cloud formation, the heat and light the Earth radiates back to space, and the recycling of carbon and nitrogen.

"One of the bigger questions is, with climatic extremes and predicted climatic change, what will be the impact on the atmosphere and back to the land surface? So we're looking at a complex system and fire is one of the important processes," he said.

To enhance fire detection, NASA says it is developing improved sensors with better optics and bigger antennas to send back better data.