Using satellites to track fire
What are satellites, and why do we use them to examine fire? Satellites are objects which orbit larger other objects in space. There are two types of satellites: natural, like our moon, which orbits the Earth, and artificial, which are created and launched into orbit by humans.
Image Credit: European Space Agency
Artificial satellites allow us to view the effects of fire from space, to observe patterns and take measurements that are not visible with the human eye, or are difficult to detect on the ground. Satellites see things that we cannot. There are currently over 1,000 active satellites and over 2,000 inactive artificial satellites orbiting Earth. These satellites range in size from as large as a school bus to about the size of a loaf of bread. To see a model of the satellites currently orbiting our planet, check out Stuff in Space.
Satellites are useful because the human eye actually can only see a small portion of the wavelengths of light that exist in the universe. All the wavelengths combined are called the Electromagnetic Spectrum (EM Spectrum). Humans can only see the portion that we call visible light. But the portions of the EM Spectrum which we cannot see give us deeper insight into the workings of our planet.Image credit: NASA
When a satellite takes an image from space, it operates in a similar fashion to the human eye: it observes the reflected light across different sections of the Electromagnetic Spectrum. Unlike the human eye however, satellites can observe light outside of the visible spectrum, including infrared and ultraviolet light. For information more about the Electromagnetic Spectrum, visit: http://earthsky.org/space/what-is-the-electromagnetic-spectrum
In this lesson, you will be examining two types of satellite images: True Color Images, which show the earth as it is seen to the human eye, and False Color Infrared Images, which use wavelengths outside the range of human vision, such as infrared or ultraviolet radiation. False color images work by converting data collected by satellites into colors visible to the human eye, so that we can see them too. This lesson uses imagery collected from NASA’s Landsat 8 satellite, in 2014. Each pixel in a Landsat image represents an area 30 meters 30 meters on the ground, or 900 square meters. That means that anything smaller than that size isn’t detectable on the satellite image. However, this resolution still allows us to view changes over a large area. The Landsat program has provided imagery from all over the Earth since 1972. It’s been running for so long, that it’s ideal for examining how landscapes change over time.
Why use False-Color Infrared images? When we look at a True-Color satellite image of the prescribed burn in Blackwater River State Forest, we can see that a fire is present, but its location is hidden under the smoke.
But when we look at the same image while substituting Infrared light for red light and Near-Infrared (NIR) light for green light, we are able to see through the smoke and identify the fire’s exact location.
Another noticeable difference between the two images is that the False-Color Infrared image appears significantly greener. Healthy vegetation reflects more NIR than bare ground. This makes it easier to distinguish between land that is vegetated, such as forests, fields, and parks, and areas that are roads, bare earth, and population centers.