Days after it began aligning the mirrors, the James Webb Telescope locked onto a guide star using its Fine Guidance Sensor to keep the telescope pointed to high accuracy. Engineers fired the Fine Guidance Sensor for aliveness and functional tests on January 28 after the telescope’s first detection of starlight in the Near-Infrared Camera (NIRCam).
The sensor, along with the Near-Infrared Imager and Slitless Spectrograph, has been developed by Canada. Measures the exact position of a guide star in its field of view 16 times per second and sends adjustments to the telescope’s fine steering mirror about three times per second.
René Doyon and Nathalie Ouellette, principal investigators for FGS and NIRISS said that the sensor is so powerful that a person in New York City could see the eye movements of someone blinking at the Canadian border 500 kilometers away.
“Webb’s 18 primary mirror segments not yet aligned, so each star appears as 18 duplicate images. On Feb. 13, FGS successfully locked onto and tracked one of these star images for the first time,” the engineers said adding that they thrilled to see this ‘closed-loop guiding’ working. They launched the telescope to probe farther into our origins from the Universe’s first galaxies to the birth of stars and planets.
Noted that the engineers will now use the FGS guidance for most of the alignment process of the telescope mirrors, providing diagnostic information for mirror adjustments. The telescope in a three-month commissioning phase as it received the first photons of starlight that traveled through the entire observatory and detected by the Near Infrared Camera (NIRCam) instrument.
The process of aligning the telescope practiced several times on the ground before putting it to use in the vacuum of space.
The James Webb Space Telescope, a successor to the legendary Hubble Space Telescope, launched from Europe’s Spaceport in French Guiana in December on board the powerful Ariane-5 rocket to a destination nearly 15,00,000 kilometers away from its home planet.
Developed by scientists, engineers from 14 countries of the world, the telescope required 40 million hours of work to be ready before locked on top of the rocket. The telescope is so sensitive that it can theoretically detect the heat coming from a bumblebee located at the distance of the Moon from Earth.
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