Laura Nielsen for Frontier Scientists –
Every eight days, a Landsat satellite carrying delicate sensing and scanning equipment passes high above wherever you might be on the planet. Data from Landsat mission images records changes on Earth's surface since 1972, over the last four decades, and it's freely available to scientists and the public. By visiting Earthshots: Satellite Images of Environmental Change, you can explore how the surface of our planet has transformed over time.
The Landsat initiative is a joint program undertaken by the National Aeronautics and Space Administration (NASA) and the U.S. Geological Survey (USGS). Early stirrings of the project can be traced back to 1966, with a push to begin project EROS, Earth Resources Observation and Sciences, intended to accrue natural resource information from images obtained by orbiting satellites. At the time, Secretary of the Interior Stewart Udall stated: “The time is now right and urgent to apply space technology towards the solution of many pressing natural resources problems being compounded by population and industrial growth.”
Our struggle to envision and understand humanity's impact on the environment and vice versa continues today. Remote sensing tools like the Landsat satellites can help monitor natural and human-induced changes to Earth's environment over time.
Data from Landsat helps rescue workers target their efforts by supplying images of towns before and after natural disasters like tornado strikes. It allows for better forest management and helps track deforestation rates. Remote sensing tools aid in fire science like wildfire control planning. Agricultural planners look at Landsat images to understand water resources, forecast crop success and plot how invasive species damage local plants. City planners use timeline Landsat images to map how urban areas enlarge and change.
Some applications are easy to imagine, like watching the realities of sea ice thinning and melting, or glaciers expelling ice into the sea. Some might be less expected, like studying cloud cover to understand how much it promotes warmth or encourages cooling. And other applications are downright creative. Eareckson Air Station is located on Shemya Island, in the remote far west of Alaska's Aleutian Islands. Satellite imagery mapping the snow line and vegetative health is used to forecast a critical period when large (formerly endangered) migratory Aleutian Cackling Geese stop-over at the islands. The air base decreases activity for a few days each spring and fall while the flock is likely to be present on nearby islands in order to mitigate the likelihood of midair strikes.
Landsat satellites obtain data from regions that are difficult or impractical for humans to reach, like the far-north Arctic and Antarctica. They also show more than the human eye is capable of seeing by sampling light reflecting off Earth's surface from a wide range of the electromagnetic spectrum (representing the range of energy that comes from the sun). When you see a satellite image in false color, that most often means a Landsat satellite has sampled light in the non-visible spectrum. The non-visible light is assigned a visible color, to allow scientists to analyze the data. In false-color images, vegetation is often portrayed as red because leafy plants reflect near-infrared light very well and the near-infrared data has been assigned a red color.
The two currently-operating Landsat spacecraft, Landsat 7 and Landsat 8, each orbit the Earth once every 99 minutes, which means they cover the same track every 16 days. Working together, the satellites can provide images once every 8 days of any region on Earth. Their instruments' range covers a 115 mile wide swath [185 kilometer wide], and every pixel in a Landsat image represents an area of about 90 x 90 feet.
The U.S. Geological Survey's EROS Center has millions of Landsat scenes archived, creating a long-term record of natural and human induced changes on Earth's landscape. You can freely access this unprecedented record of global land images from space. Pretty amazing.
Frontier Scientists: presenting scientific discovery in the Arctic and beyond
- 'An Idea That Worked' U.S. Geological Survey (2007)
- 'Earthshots: Satellite Images of Environmental Change' U.S. Geological Survey (2013)
- 'How Landsat Helps' National Aeronautics And Space Administration (2013)
- 'Landsat Mission Data' U.S. Geological Survey (2013)
- 'Landsat Stories: Analyzing Landsat to Mitigate Bird/Aircraft collisions' U.S. Geological Survey (2012)
- 'Timelapse' TIME, powered by Google (2013)