James Webb telescope passes inspection after months in extreme cold

The James Webb Space Telescope, likely to launch in spring 2019, appears to have passed tests by NASA scientists for good after it was removed from a very cold vacuum chamber in December 2017.

According to Bill Ochs, a project manager for the James Webb telescope, the alignment of the primary mirror’s eighteen mirror elements with the scientific instruments has been verified, CBS reports. Furthermore, the image quality has been successfully tested and the device performed correctly in the extreme cold of about -250 degrees Celsius.

At the end of November, Ochs already announced that the telescope had passed the cryogenic tests. The project’s scientists tested the optical telescope and integrated science instrument module for 100 days in 2017 to ensure they function properly in the extreme cold and vacuum of space. According to Ochs, it has now been definitively verified that the James Webb will perform well in these extreme conditions.

In space, the telescope operates at -233 degrees Celsius; the telescope must be very cold to pick up the faint infrared light from distant space objects. The so-called mid-infrared instrument, a spectrograph that mainly analyzes the light from warm exoplanets, must even work in -266 degrees Celsius. A special cooling system has been installed for this.

The James Webb Space Telescope will not orbit the Earth like the Hubble, but rather orbit the Sun, at a distance of 1.5 million kilometers from Earth. This point is also called the Lagrange point L2. In that spot, the telescope stays out of the shadows of the Earth and the Moon. The sun shield blocks the light and heat of the sun, earth and moon. This is necessary for the telescope to detect infrared light from distant objects as well as possible. Incidentally, at the front of the sunshade it is 85 degrees Celsius, while the telescope on the other side of the sunshade operates in -233 degrees Celsius.