May 7, 2013
NASA Observes Volcanoes From Space Using Thermal Imaging
Brett Smith for redOrbit.com - Your Universe Online
By using both optical and thermal sensing instruments onboard the Landsat Data Continuity Mission (LDCM) satellite, NASA scientists were able to create a comprehensive image of the Pacific´s Paluweh volcano in mid-eruption.
Taken on April 29, 2013, the images show the island volcano with a plume of ash appearing to drift northwest and over Indonesia's Flores Sea. While the satellite's Operational Land Imager detected the white cloud of smoke and ash, the Thermal Infrared Sensor (TIRS) on the LDCM picked up thermal details of the eruption, including the white-hot speck in the volcano´s caldera.
According to official data from the Smithsonian Institute, the Paluweh volcano spewed ash 7,000 to 10,000 feet into the air during its late April eruption.
Betsy Forsbacka, TIRS instrument manager at NASA's Goddard Space Flight Center in Greenbelt, MD, said the two instruments working in concert allowed for researchers to gain more insight than either one could have provided independently.
"Each instrument by itself is magnificent," she said. "When you put them together, with the clues that each give you on what you're seeing on Earth's surface, it's greater than either could do by themselves."
NASA said the thermal image of the volcano showed off TIRS' abilities to capture the specific boundaries between the hot volcanic activity and the relatively cooler cloud of volcanic ash — as other satellite images may have shown the hot spot bleeding over into the cooler surrounding areas.
To reach this degree of image refinement, TIRS engineers tested and calibrated the instrument pre-launch, pixel-by-pixel. Without this degree of fine tuning, the images from Paluweh may have come out overexposed — showing spots and halos where the images should be dark, the researchers noted in a statement.
"We can image the white, representing the very hot lava, and right next to it we image the gray and black from the cooler surrounding ash," Forsbacka said. "It's exciting that we're imaging such diverse thermal activity so well."
The TIRS instrument is also capable of detecting subtle shifts of temperatures to within a tenth of one degree Celsius. Forsbacka added that taking Earth's temperature from space can be difficult because the atmosphere disrupts thermal signals from the ground. However, the satellite´s two different thermal bands enable an easier removal of atmospheric ℠noise´ than other previous models. To estimate surface temperatures before, scientists that used single thermal band satellites needed additional measurements or data about atmospheric conditions.
Because the atmosphere affects each thermal band a bit differently, one thermal image is typically darker than the other. The NASA scientists use this difference to compensate for atmospheric effects and generate a more exact temperature measurement of the Earth's surface.
Currently, the Landsat program is a joint venture between NASA and the US Geological Survey. Once LDCM finishes its onboard calibration and testing phases later this month, it is scheduled to be handed over to the USGS and renamed Landsat 8. NASA said data from TIRS will be processed, stored and disseminated from the USGS for free online. The Landsat program has been in operation since 1972.