Cosmic Eye Exam Shows Jaw-Dropping Accuracy of Webb Telescope's Optics

The scope's main mirror must hold its shape even down to temperatures near absolute zero.

Saturday, September 03, 2011

THE MOMENT  NASA engineer Ernie Wright examines 6 of the 18 segments of the James Webb Space Telescope’s primary mirror in preparation for a final round of testing at Marshall Space Flight Center in Huntsville, Alabama. A laser system called an interferometer measures how the mirrors warp as they cool from room temperature to –415 degrees Fahrenheit, slightly below their normal operating range in space. The mirrors must hold their shape to within 25 billionths of a meter to perform properly.

THE SHOT  Photographer 
David Higginbotham set 
remote flashes in front of himself and Wright to light the chamber. He held his Nikon D3 a bit above his eyes so the camera would not appear in the mirrors. The texture seen in the mirrors is the magnified reflection of a seam on Higginbotham’s clean-room suit.

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