Weber released 1560 image for the first time, with 54G data: How does the Weber telescope focus?

Space telescope can be said to be the main observation tool for astronomers. One of the most famous is the Hubble telescope, which we have been exposed to since childhood. 1990, Hubble telescope, the strongest and largest optical telescope in human history, was born and started its career.

Since the service of 18, Hubble has photographed all kinds of thrilling and magnificent scenes after the explosion of many galaxies in the universe, which has made great contributions to the progress of astronomy. 202165438+On February 25th, James Webb Space Telescope JWST officially joined the Space Telescope Club and took over the baton of Hubble Telescope.

As the successor of Hubble telescope, the name "james webb" is taken from james webb, the second director of NASA. During his tenure as the leader of NASA, the American space industry opened a new chapter, including the exploration of the moon and the Apollo moon landing program.

On the evening of February 1 1, 2022, NASA officially released the first image taken by the Webb telescope. JWST successfully shot and sent back a group of photos of stars and the first "selfie". The first set of star photos shows the starlight of the same star captured by the 18 primary mirror of the Weber telescope.

From the picture, this photo of 18 highlights looks very dull. However, it shows that the first phase of the calibration of the Webb telescope is about to be completed. Earlier, NASA said that the Webb telescope needed to focus on the star HD84406. What is the principle of this work and how is it completed?

As we all know, the main mirror of the Weber telescope consists of 18 independent auxiliary mirrors. Therefore, in order to make these independent sub-mirrors accurately and completely spliced into a main mirror for optical imaging, the Weber telescope needs a series of shooting and debugging work.

Weber telescope uses near-infrared camera NIRCam to aim at the main mirror. First, it is confirmed that the near-infrared camera NIRCam is ready to collect celestial light, and then the starlight of the same star is identified from each main lens of 18.

First, the Webber telescope will first point to a bright isolated star HD 84406 in Ursa Major. This star is chosen because it is easy to identify and is not easily disturbed by other stars with similar brightness. Each point in the composite image is marked with its corresponding main lens number.

On February 2, 2022, the Weber telescope began the first image capture process. It first points to the pre-calculated position of the star HD 84406. At 156 different positions around, near-infrared camera NIRCam was used to generate 10 detectors for the main mirror, and 10 groups were photographed, accounting for 1560 images.

The whole process lasted nearly 25 hours, and the original data was 54 g. Within 6 hours of alignment and 14 exposures, the position of the target star in each sub-lens was determined. Subsequently, the Weber telescope stitched these images together to form a composite image with more than 2 billion pixels.

At the center of this super-large image file is the 18 mirror of the Weber telescope, and 18 images of the star HD 84406 are made respectively. Then, the Webber telescope began to adjust the mirror surface of 18, and the imaging mirror surface corresponding to these bright spots can be determined.

After the image matches the mirror, the mirror tilts. An image array is formed according to the arrangement of mirrors. Then, the secondary mirror of the Weber telescope is slightly moved to defocus, so that the error can be presented by a special algorithm. NASA uses a phase correction algorithm to correct various errors caused by the secondary mirror.

"After further adjustment, the entire Weber team was ecstatic. Because the first step of taking images and calibrating the telescope went very smoothly. " Marcia Rieke, academic leader of near-infrared camera and professor of astronomy at the University of Arizona, said.

Lee Feinberg, the component manager of the Weber Optical Telescope at NASA Goddard Space Flight Center, explained the early stage of the mirror alignment process: after this adjustment, the 18 sub-mirrors have been well calibrated, and they can all image by themselves. Next, we combine the 18 mirror into a complete main mirror to work.

The images generated by 18 secondary mirrors are superimposed, and 18 stars gather in the center to become the intersection point. In this step, according to the program setting, the sub-lens of 18 is divided into three groups, and superimposed in the grouping order until it successfully intersects at one point. But so far, the debugging work is not over.

Nasa said: in image mosaic, any visible point is imaged by the lens in 18 sub-lens. After debugging and determining the calibration position of each sub-lens, it is the key first step for Weber telescope to complete calibration and produce scientific images.

In order to make the assembly achieve the required accuracy, NASA uses dispersion fringe sensing technology for error detection and auxiliary adjustment of thickness. The spatial frequency of dispersion fringes can reflect the magnitude of translation error and can be used as a benchmark for adjustment. After the initial * * * direction adjustment, it is still adjusted by * * *.

Subsequently, NASA adopted defocus contrast method to achieve higher accuracy requirements. After three times of * * * phase and two times of defocusing, the first phase of the Weber telescope was initially realized. Therefore, with this success, the Webb telescope will officially begin its deep space exploration journey! Are you looking forward to its new photos?