Although until June - if all goes according to plan - we will not see the first images from the James Webb Space Telescope this week the NIRCam began to capture light. It is as if the telescope opened its eyes for the first time. Although in the case of the Webb it is still a look multiplied by 18 and out of focus that only captures useful images to align and focus the telescope, which is no small thing. But they are not images that NASA is going to publish.
✨ Our NIRCam instrument's detectors saw their 1st photons of starlight! While #NASAWebb is not yet ready for science, this is the first of many steps to capture images that are at first unfocused, used to slowly fine-tune the optics: https://t.co/Sak6r7Ncex #UnfoldTheUniverse pic.twitter.com/vHRX8x9ki2
— NASA Webb Telescope (@NASAWebb) February 3, 2022
Multiplied by 18 because once released from their launch position each of the 18 individual segments of the primary mirror will be pointing in a slightly different direction. Out of focus because also its curvature is not adjusted yet . In fact, the fact that the NIRCam has begun to see is nothing but a previous step to be able to start the process of aligning and focusing the telescope, which, roughly speaking , consists of these steps:
- Identification of the image of each segment to know which image is of each mirror.
- Alignment of segments so that the image of each of them is at a certain and controlled point.
- Image stacking so that all 16 images fall into a single point.
- Coarse focus with the curvature of the individual mirrors.
- Fine focus with the internal optics of the Webb's instruments.
- Alignment for the other instruments , and it is that in the previous steps it only works with the NIRCam.
- Final alignment once adjustments have been made for each instrument.
But before starting with these seven steps , both the instruments, turned on a few days ago, and the mirrors still have to cool down.