The first six of 18 segments of NASA's James Webb Space Telescope's primary mirror for space observations begin a round of cryogenic testing to confirm the mirrors' response to the extreme temperatures of space. The X-ray and Cryogenic Facility at NASA's Marshall Space Flight Center in Huntsville, Alabama will provide the space-like environment to help engineers measure how well the telescope will image infrared sources once in orbit. Each mirror segment measures approximately 4.3 feet (1.3 meters) in diameter to form the 21.3 foot (6.5 meters), hexagonal telescope mirror assembly critical for infrared observations. Each of the 18 hexagonal-shaped mirror assemblies weighs approximately 88 pounds (40 kilograms). The mirrors are made of a light and strong metal called beryllium, and coated with a microscopically thin coat of gold to enabling the mirror to efficiently collect light.