NASA’s James Webb Space Telescope Ready for Calibration After Cooling

The James Webb Space Telescope goes one step further to probe the depths of the universe. On Wednesday, NASA that it was ready to begin JWST optical alignment and test imaging after the telescope’s instrumentation reached its final operating temperature of minus 448 degrees Fahrenheit (or minus 267 degrees Celsius) on last week.

JWST has gradually cooled down since its success but the telescope took an important step on that front when its giant 70-foot-tall sunshade earlier in the year. That component allows JWST’s systems, including its mission-critical Mid-Range Infrared (MIRI), to drop to temperatures of about minus 298 degrees Fahrenheit (or about minus 183 degrees Celsius).

For JWST to reach its final operating temperature, NASA and the European Space Agency must activate the telescope’s electrical “cooler”. That in itself involved overcoming a technical hurdle known as the “pinch point,” or the stage where James Webb’s instruments went from minus 433 degrees Fahrenheit to minus 448 degrees Fahrenheit.

“The MIRI Cooling team has put a lot of work into developing the process for the pinch point,” said Analyn Schneider, MIRI project manager for NASA’s Jet Propulsion Laboratory. “The whole team is both excited and nervous about entering the important activity. In the end, it was a textbook execution, and cooler performance was even better than expected.”

Part of the reason James Webb needed to be so cold before starting the mission was so that its electronics would produce as little infrared light as possible and thus be less likely to interfere with its devices when the astronomers direct them to distant cosmic bodies. Cold temperatures are also required to avoid something called “dark currents,” an electrical force produced when atoms in a telescope’s detector vibrate. That motion can produce false signals that make it difficult for telescopes to get an accurate picture of an object.