Nasa Confirms The Webb Telescope Has Successfully Detected Its First Photons

Over a week after arriving at the second Lagrangian point (L2) from where it will observe the birth of our universe, the James Webb Telescope began its three-month-long process to align the mirrors. The telescope received the first photons of starlight that traveled through the entire observatory and were detected by the Near Infrared Camera (NIRCam) instrument.

This marks the beginning of the aligning process of the 18 mirrors to direct light onto one to observe the infrared light coming from distant worlds, galaxies, and the origin of our universe. The data from the NIRCam will be used by engineers at Ball Aerospace, Space Telescope Science Institute, and NASA’s Goddard Space Flight Center to align the telescope.

"This milestone marks the first of many steps to capture images that are at first unfocused and use them to slowly fine-tune the telescope. This is the very beginning of the process, but so far the initial results match expectations and simulations," Nasa said in a statement.


The process of aligning the telescope has been practiced several times on the ground before putting it to use in the vacuum of space. The team has developed a 1/6th scale model telescope to conduct tests. Over the next three months, the telescope will be aligned in seven phases, followed by commissioning of the instruments onboard.

Nasa, however, cleared that the images taken by Webb during this period will not be “pretty” like the new views of the universe Webb will unveil later this summer. They strictly serve the purpose of preparing the telescope for science. The US space agency said that to work together, the telescope’s 18 primary mirror segments need to match each other to a fraction of a wavelength of light approximately 50 nanometers.


Aligning the mirrors involves seven steps:

Segment Image Identification: Aligning the telescope relative to the spacecraft using the isolated star (HD 84406) to capture a series of images that are then stitched together to form a picture of that part of the sky.

Segment Alignment: This process corrects most of the large positioning errors of the mirror segments as the team begin by defocusing the segment images by moving the secondary mirror slightly.

Image Stacking: The team will move the individual segment images so that they fall precisely at the center of the field to produce one unified image.

Coarse Phasing: The segments need to be lined up with each other with an accuracy smaller than the wavelength of the light. Coarse Phasing measures and corrects the vertical displacement (piston difference) of the mirror segments.

Fine Phasing: These operations measure and correct the remaining alignment errors using the same defocusing method applied during Segment Alignment.

Telescope Alignment Over Instrument Fields of View: In this phase of the commissioning process, the team will make measurements at multiple locations, or field points, across each of the science instruments

Iterate Alignment for Final Correction: After applying the Field of View correction, the key thing left to address is the removal of any small, residual positioning errors in the primary mirror segments.

The telescope will capture the first images five months from now as the world awaits to see the images from the birth of our universe.

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