James Webb Space Telescope sunshade deployment begins in critical milestone for $10 billion mission

Now well beyond the moon, the James Webb Space Telescope has begun a nail-biting series of steps to safely unfurl the observatory's fragile sunshield.

The five-layer sunshade, the size of a tennis court, is required to block out the sun and cool Webb's optics and instruments to within 50 degrees of absolute zero, or minus-370 Fahrenheit. Only then will the telescope be able to register the faint infrared light from the first generation of stars and galaxies.

Sunshade deployment is considered one of the riskiest aspects of the $10 billion mission, one that simply has to work as planned or Webb's science will be degraded. Extraordinary tests were carried out on the ground to make sure the deployment would work as planned, but there are no guarantees.