On Feb. 11, NASA held a teleconference where they talked about how the James Webb optics are adjusted, and presented some of the first images taken by the telescope during the adjustment. Optician Lee Feinberg, James Webb Project Scientist Marshall Perrin, and Marcia Riquet, Leading NIRCam Specialist and Professor of Astronomy at the University of Arizona at Tucson spoke about the observatory.
The telescope is moving towards the completion of the first phase of a months-long process of aligning the observatory's primary mirror with the NIRCam near-IR camera, according to NASA experts. The project engineers had two main tasks - to check that NIRCam is capable of collecting light from space objects, and then adjust the optics so that each of the 18 segments of the main mirror can capture light from the first target of James Webb - HD 84406 star.
NASA spoke about how the optics will be adjusted in early February of this year. First, Webb will take a series of defocused images of HD 84406. These images will be used to adjust the position of each of the telescope's 18 mirrors and work out the alignment of the optics. The team of engineers will have to align the telescope's optics to within a fraction of a wavelength of light - roughly 50 nanometers, NASA has indicated. In total, seven stages of adjustment are planned, which, if necessary, specialists will repeat: identification of an image segment; segment alignment; image overlay; rough phasing; precise phasing; alignment of the telescope to the fields of view of the instrument; final adjustment of the equipment.
The first stage is almost completed. Below is a mosaic of 18 images of HD 84406 taken with different segments of the telescope. NASA has warned that the first images will be ugly in the broad sense of the word. They are needed solely to adjust the telescope and, once it is completed, the engineers will transfer it to a less bright and more distant object.
Below is the same collage, only with marks to which segment of the mirror this or that image of a star belongs. On the left, for convenience, the location of the segments on the main mirror is marked. As NASA points out, during the imaging process, which began on February 2, the telescope changed 156 different positions around the estimated location of the star and generated 1,560 images on 54 gigabytes of raw data. The whole process took 25 hours. After that, the images were stitched together to obtain a single mosaic, reflecting the state of each segment of the main mirror in one frame. The published collage is just part of a larger mosaic - a huge image with more than 2 billion pixels.
NIRCam has a wide field of view and the unique ability to operate safely at higher temperatures than other instruments require. That is why he was chosen for the initial setting of "James Webb". In addition, the tool is equipped with individual components designed specifically for these processes.
NASA notes that NIRCam is now operating at temperatures well above the ideal (for this instrument), so there are a lot of artifacts in the images. These artifacts are clearly visible in the telescope selfie. It seems that there is dust or scratches on the optics, but in fact this is not the case. As the camera cools, there will be fewer artifacts.
The telescope selfie was created using a special tool inside NIRCam designed to capture a telescope instead of space. These configurations will not be used in scientific research, they are only required for tuning.
At the moment everything is going according to plan. According to engineers, "James Webb" is in working order, the calibration of optics is proceeding according to plan. In the future, images will get better, and eventually, this summer, NASA experts will present the first full-fledged images of distant space objects.
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