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How does FAST observe different parts of the sky even though its main dish does not move?
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Telescope
Aerial view of the Keck Observatory's twin domes, which are opened to reveal the telescopes. Keck II is on the left and Keck I on the right.
Although the main dish of the Five-hundred-metre Aperture Spherical Telescope (FAST) is fixed within a natural depression and does not move, it can observe different parts of the sky within 40 degrees of the zenith through two primary mechanisms:12
- Changeable Surface: The shape of the telescope's spherical reflector is adjustable, allowing it to deform its surface to maintain focus as it tracks celestial objects.1
- Moving Feed Cabin: The feed cabin, which is the component where radio waves are focused, is suspended from six cables above the dish. This cabin can move around the surface of the dish to capture signals from different directions.1
By combining these two features, FAST is able to effectively scan the sky despite the immobility of its massive primary structure.1