Black Marble (Image courtesy NASA)NASA unveiled a new view of our world today. Black Marble is a new high-resolution image that shows the entire surface of the Earth at night in awe-inspiring detail.
The image is a stitched-together composite constructed from multiple images taken by the Suomi National Polar-orbiting Partnership (NPP) satellite as it made over 300 orbits of the planet. It took the satellite 22 days — 9 in April and 13 in October — to gather all the images, which were then painstakingly assembled and then overlaid onto NASA's already-existing Blue Marble composite to produce the final picture.
Sunomi NPP's Visible Infrared Imaging Radiometer Suite (VIIRS) was the key to accomplishing this. Other satellites that record visual images of the Earth only do so during the day. Once night falls, they rely only on infrared sensors to send information back to Earth about weather patterns simply based on the temperature of clouds in the atmosphere. However, although infrared images give scientists a basic view of clouds, there are some major limitations, such as not being able to see multiple layers of cloud and not detecting clouds very close to the surface.
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Rather than simply taking a single-exposure picture, VIIRS' day-night band takes multiple scans of each area it views, in visible light, infrared light and radiometric measurements. It breaks those scans down into individual pixels, recording the light intensity for each pixel, and then adjusting the brightness to compensate for any particular pixel that gets saturated or is too dark.
"It's like having three simultaneous low-light cameras operating at once and we pick the best of various cameras, depending on where we're looking in the scene," says Steve Miller, from the Cooperative Institute for Research in the Atmosphere (CIRA) at Colorado State University.
This allows it to capture very faint light sources, and thus see clouds, ocean colour, read land and ocean temperatures, view ice movement, and see the location of fires, all at night. It is also sensitive enough to pick up the light from cities, highways and other human-built sources.
There was only one other 'tweak' performed to produce the final image. VIIRS picked up all the light from all these sources, but they just aren't as impressive without some context. To provide that context, they were combined with Blue Marble — a high-resolution composite image of the Earth during the day.
I hope you'll agree that the results are spectacular.