An eye-catching new view of Earth has been caught on camera by an American spacecraft circling the moon.
The new photo of Earth was taken from a distance of 231,358 miles (372,335 km) by NASA's unmanned Lunar Reconnaissance Orbiter during a routine camera test as the probe orbited around the moon. The black-and-white snapshot catches Earth's portrait as it appeared on June 12.
"It was a beautiful clear summer day over the North Pole, you can see ice covering most of the Arctic Ocean with a few leads of open water (dark) starting to open up," wrote Mark Robinson, ?principal investigator for the powerful Lunar Reconnaissance Orbiter Camera (LROC) at Arizona State University, after posting the photo Thursday.
The photo was taken by the orbiter's narrow angle camera and has a resolution of about nearly 2.3 miles (3.7 km) per pixel. At the center of the image is Hong Kong, with much of the Middle East clearly visible. [Details of the new Earth photo.]
The image is actually a mosaic of photos taken by the lunar camera as it panned across the planet. One swirling rock formation can be seen running through parts of Iran, Afghanistan and Pakistan, Robinson wrote.
NASA launched the Lunar Reconnaissance Orbiter in June 2009 to seek out potential landing sites on the lunar surface for future missions, as well as hunt for signs of water ice. So far, the orbiter has found NASA's past Apollo moon landing sites and evidence of water on the moon (the latter with the help if its partner probe LCROSS ? which crashed into the moon last year while the orbiter watched ? and other probes).
But every now and then, mission scientists have to point the orbiter's LROC camera system at the Earth for calibration sessions.
The moon's subtle color changes make it a poor target to measure scattered light, Robinson explained. The Earth is a bright target against the ultra dark background of black space, so any image anomalies caused by scattered light (light reflecting off internal parts of the camera) are easily measured, he added.
"From the moon, the Earth serves that function well," Robinson wrote.
These calibration sessions allow scientists to fine-tune the Lunar Reconnaissance Orbiter's seven-color wide angle camera in order to account for scattered light effects in its photos. While the wide angle camera is being calibrated, the orbiter's narrow angle camera is free to snap photos of Earth from space.
"Imagine standing on the moon looking back at the Earth!" Robinson wrote. "When humans start to live and work on the nearside of the moon, they will have a constant, spectacular view of our home planet."
Until then, he added, the people of Earth will have to settle for photos from robots.
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