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NASA Closes Chamber A Door to Commence Webb Telescope Testing

The vault-like, 40-foot diameter, 40-ton door of NASA’s Johnson Space Center’s historic Chamber A sealed shut on July 10, 2017, signaling the beginning of about 100 days of cryogenic testing for NASA’s James Webb Space Telescope in Houston.

Don’t be fooled by Chamber A’s now monolithic look. Behind the hulking door, the process to transform the chamber’s interior to match the airless, frigid environment of space will soon begin. It will take about 10 days to pull the air from the chamber, and then about one month to lower the temperatures of the Webb telescope and its scientific instruments to the levels required for testing.

Chamber A door
Engineers watch as Chamber A’s colossal door closes at NASA’s Johnson Space Center in Houston.
Credits: NASA/Chris Gunn

Though the Webb telescope will be enveloped in darkness, the engineers testing the telescope will be far from blind. “There are many thermal sensors that monitor temperatures of the telescope and the support equipment,” said Gary Matthews, an integration and testing engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is testing the Webb telescope while it is at Johnson. “Specialized camera systems track the physical position of the hardware inside the chamber, monitoring how Webb moves as it gets colder.”

Chamber A
Chamber A’s sealed, vault-like door towers over engineers at NASA’s Johnson Space Center in Houston.
Credits: NASA/Chris Gunn

In space, the telescope must be kept extremely cold, in order to be able to detect the infrared light from very faint, distant objects. To protect the telescope from external sources of light and heat (like the sun, Earth and moon), as well as from heat emitted by the observatory, a five-layer, tennis court-sized sunshield acts like a parasol that provides shade. The sunshield separates the observatory into a warm, sun-facing side (reaching temperatures close to 185 degrees Fahrenheit) and a cold side (400 degrees below zero). The sunshield blocks sunlight from interfering with the sensitive telescope instruments.

The James Webb Space Telescope is the scientific successor to NASA’s Hubble Space Telescope. It will be the most powerful space telescope ever built. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

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By Eric Villard
NASA’s Goddard Space Flight Center, Greenbelt, Md.