How a satellite actually creates images of the Earth

Illustration for article titled How a satellite actually creates images of the Earth

On February 11, 2013, NASA's Earth-mapping Landsat 8 satellite was launched into our planet's orbit. To celebrate a year in space, Landsat team leader David Roy has used imagery acquired by the satellite to create a most unusual composite photograph of the United States: a patchwork of parallel strips, each one 115-miles wide.

Image Credit: NASA/David Roy | Click here to see it in overwhelmingly hi-res

The map's "swaths," as they're called, reflect the way that Landsat 8 acquires images of Earth. Via NASA:

Like its predecessors, Landsat 8 collects data in 185-kilometer (115-mile) wide strips called swaths or paths. Each orbit follows a predetermined ground track so that the same path is imaged each time an orbit is repeated. It takes 233 paths and 16 days to cover all of the land on Earth. This means that every land surface has the potential to be imaged once every 16 days, giving Roy two or three opportunities to get a cloud-free view of each pixel in the United States in a month.


Less than a year in space and already scientists are making incredible use of Landsat 8 and its impressive suite of instruments. One of my favorite examples: back in December, researchers announced they'd used the satellite's Thermal Infrared Sensor to home in on the coldest place on Earth. (Also worth checking out are Google's interactive time-lapse views of Earth, assembled from images acquired by Landsat 8 and its predecessors over the last three decades.)



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I work on the Landsat project, and David Roy is a close associate of mine. But I need to correct this: Landsat is a USGS satellite. NASA helped build it, but the USGS pays for operations and owns it.

This comes up a lot because NASA is very, very good at public relations. That's the reason you're seeing a dispatch from David Roy, while you may have missed ours. NASA puts out cool stuff to grab attention; we put out useful stuff, but we're not so good at capturing the cool. (Blame bureaucracy.)