Re:Starlink is now Accepting General Pre-orders
by sandworm101 on Thursday February 18, 2021 @08:38PM
(#26188423)
No. The beams would overlap, which is fine of they are on different frequencies, but eventually you run out of frequencies to use. Fiber confines the beam to inside the fiber. No overlap between one fiber and another means you can run multiple down the same pipe.
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Re:Starlink is now Accepting General Pre-orders
by mleonhard on Friday February 19, 2021 @02:10AM
(#26190520)
Why would they overlap?
Re:Starlink is now Accepting General Pre-orders
by Melkman on Friday February 19, 2021 @09:35PM
(#26200950)
Because a beam in an open medium always diverges due to wavefront errors and diffraction. A very good laser system might possibly have a divergence of only 1 microradians. For reference a typical laser pointer has a divergence angle of 1 to 2 milliradians. With the 2000km or so between satellites for Starlink the laser "spot" on the receiving satellite with the very good laser will be about 2 meter. Not enough to receive multiple beams on one satellite without overlapping.
Re:Starlink is now Accepting General Pre-orders
by mleonhard on Saturday February 20, 2021 @12:01AM
(#26201729)
Thanks for explaining. Would it work if they put receivers on a long pole, spaced 3m apart? Maybe they could mount them on the edge of the solar panel array, which is ~30m long [0].
[0] https://lilibots.blogspot.com/2020/04/starlink-satellite-dim...
Re:Starlink is now Accepting General Pre-orders
by Melkman on Saturday February 20, 2021 @05:54AM
(#26203235)
The link estimates the surface of the panels to be 30m2. Since the panels are 3.1m wide the length would be 9.6 meters. But even at 30 meters it would be very very hard to engineer a system that can keep a laser beam aligned on a moving target with sub microradian precision. I'd guess Starlink laser are more divergent to make hitting the target easier. Keeps the exit pupil a manageable size too (narrower beams need bigger optics).