James Webb Space Telescope Locked Onto Guide Star for High Accuracy Mirror Alignment
upstart writes:
James Webb Space Telescope Locked Onto Guide Star for High Accuracy Mirror Alignment:
After starting the mirror alignment with Webb's first detection of starlight in the Near-Infrared Camera (NIRCam), the telescope team is hard at work on the next steps for commissioning the telescope. To make more progress, the team needs to use another instrument, the Fine Guidance Sensor, to lock onto a guide star and keep the telescope pointed to high accuracy. We have asked Rene Doyon and Nathalie Ouellette of the Universite de Montreal to explain how Webb uses its Canadian instrument in this process.
"After being powered on January 28, 2022, and undergoing successful aliveness and functional tests, Webb's Fine Guidance Sensor (FGS) has now successfully performed its very first guiding operation! Together with the Near-Infrared Imager and Slitless Spectrograph (NIRISS), the FGS is one of Canada's contributions to the mission.
"To ensure Webb stays locked on its celestial targets, the FGS 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. In addition to its speed, the FGS also needs to be incredibly precise. The degree of precision with which it can detect changes in the pointing to a celestial object is the equivalent of a person in New York City being able to see the eye motion of someone blinking at the Canadian border 500 kilometers (311 miles) away!
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