NASA begins month-long commissioning of James Webb Space Telescope; instruments turned on

A week after arriving at the final destination at the second Lagrange point (L2), the James Webb Space Telescope’s commissioning phase has begun. NASA said that the operation team worked through a critical series of steps, that included powering on all of Webb’s science instruments and will now turn off heaters to commence a long cooldown process. Launched on December 5 from the Kourou spaceport in French Guiana, the $10-billion telescope reached the Lagrange point on January 25 after a 15 lakh kilometre-long journey. 

Cooling Webb's instruments the next step

In the latest Twitter update, NASA informed that all of the telescope's four instruments have been turned on. Webb is equipped with a total of four instruments, which include the Near-Infrared Camera (NIRcam), the Mid Infrared Instrument (MIRI), the Fine Guidance Sensor (FGS) and the Near-Infrared Spectrographs (NIRSpec). The next step includes turning off the instrument heaters, which were necessary to keep critical optics warm to prevent the risk of water and ice condensation. 

Once the heaters are turned off, the four instruments would take a month before they cool down to the final temperatures. NASA says that Webb’s optics team began the meticulous moving of the 18 primary mirror segments to form a single mirror surface after the NIRCam reaches -153 degrees Celsius. The NIRCam, along with NIRSpec and FGS was the last instrument to be turned on, the first being the MIRI. "Cooling of the telescope and instruments will also continue over the next month, with the near-infrared instruments ultimately reaching 37-39 kelvins. The cryocooler will cool MIRI to 6 kelvins in the following months", NASA said in its blog.

While the cooling process transpires, the engineers will also try to align the telescope's golden mirrors before it points toward its first target. NASA revealed that it has chosen the Sun-like star HD 84406 as Webb's first target, as scientists aim to warm up Webb by capturing the star's photons on the primary camera. Webb's detectors will be focused on the star for the first few weeks of mirror alignment. The agency explained that in its first observation, the telescope will create an image of 18 random, blurry points of light, which after processing will become a focused image of a single star. 

Image: Twitter/@NASA