The making of NASA's super hi-res blue marble Earth image
Some media outlets have reported that the image is the largest image ever made of our planet, but Norman Kuring, the NASA oceanographer who actually made the image, told The Times that simply is not true.
"I'm surprised that it's gone viral," he said. "I think what's happening in the general public is seeing a larger image than they are used to seeing, but there have been higher sensing instruments around for a number of years."
Kuring explained that this particular image was made using data collected by the Visible Infrared Imager Radiometer Suite, which is on a satellite flying 512 miles above the Earth. VIIRS is not really a camera -- rather it has a scanning telescope that measures the difference between the amount of light coming down to the surface of Earth from the sun as compared to the amount of light that is reflected back to the telescope. Kuring made the image above by running code that translates that data into an image.
VIIRS only scans one swatch of Earth at a time, measuring about 1,900 miles across. Kuringer says you can think of it as if you were walking down the street with a broom and sweeping as you go. The images are then pieced together to make a whole.
The satellite it rides on -- Suomi NPP, which was launched in October -- has been placed in a sun-synchronous orbit so that the satellite is over the equator at the same local ground time in each orbit. This is relevant because it explains why each slice of image is lit the same way even though the entire image of the Earth was taken over a period of several hours.
The data that VIIRS collects is still in the process of being calibrated, but eventually scientists will be able to use it to measure ocean temperatures, tell us the location of fires, and track cloud formations.
As for the above image, Kuringer said he made it as a favor to a NASA scientist who wanted a visual to use in a talk to the American Meteorological Society earlier this week. Kuringer settled on an image taken on Jan. 4 because it was a fairly sunny day, and he decided to focus on North America because the society is based in America.
-- Deborah Netburn
Image: A 'blue marble' image of Earth taken with the VIIRS instrument aboard NASA's satellite Suomi NPP. Credit: NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring