James Webb Powers On Its Science Instruments: What Comes Next?

The James Webb Space Telescope will be able to observe some of the most distant and ancient galaxies now it is in its new home, in orbit around the sun. Although it will be several months before it can start gathering science data, the science instruments on board the telescope have been turned on, and the first tests of each instrument are underway. The telescope's primary camera is called the Near Infrared Camera, or NIRCam, and images in the infrared wavelength. Since James Webb arrived at its orbit on January 24, 2022, all of the science instruments including NIRCam have been activated.

Now, the engineers who are responsible for each of the four instruments can begin the process of checking they are working correctly and beginning to calibrate them. This begins by turning off the heaters which have kept the instruments warm and free from ice during the telescope's journey to its orbit. Now, the telescope's temperature will be carefully, gradually reduced until it reaches a stable cool point.

NIRCam is set to reach a temperature of minus 244 degrees Fahrenheit this week. The temperature is very low due to the cold of space, and the instrument needs to be cold so that it doesn't interfere with readings. Infrared detectors are sensitive to heat, as hot objects give off infrared radiation. Having the instrument at a low temperature means it will be more sensitive to infrared signatures coming from distant objects.

While the telescope's mirrors are being aligned, which requires nano-meter precision, NIRCam will be used to observe the star HD84406 to test whether the instrument is working.

"These first photos mean that we finally get starlight moving through the system and detected by NIRCam," said NIRCam principle investigator Marcia Rieke (via University of Arizona). "NIRCam has not been turned on since before launch; this will prove the launch didn't introduce issues for how it can work."

Don't expect these first images to be spectacular though, as the 18 segments of the mirror won't yet be in their final position, so the images will be of 18 blurry dots. Despite the aesthetic quality of the images captured in this early stage, these first tests will be absolutely invaluable for the instrument teams who will be checking that all instruments are working correctly.

NASA is expected to share a first image from the telescope with the public this summer, 2022.