Incoming rays are reflected first off the mirror surface and then off the subreflector. They are focused to a point at the receiver room. Feeds attached to different receivers, covering different frequency (wavelength) ranges, can be moved into position at the focal point because they sit on a rotating turntable in the receiver room.
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Notice that none of the incoming rays are blocked or diffracted by anything as they are reflected on the telescope structure. This "unblocked aperture" is a unique feature of the GBT design. Note too that although oriented upright in this diagram, the GBT would actually be observing a source off to the right. |
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The GBT will be fully steerable. It can move by tilting, and also by rotating. |
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