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Comment by 0xbeefcab | Hacker News Reader

Interesting there is an optical networking option for end users (claims ~6TBps). Maybe a really dumb question, but how would the end user's ground station maintain connectivity during cloudy weather? Do they have cloud-penetrating lasers from the MEO satellites? Would that interfere with aircraft, astronomy tools, etc?

Some short googling says they have lasers that clear a path for a data carrying beam, but that seems wasteful/infeasible for commercial uses

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Some info from NASA optical communication page.

"Even Earth’s atmosphere interferes with optical communications. Clouds and mist can interrupt a laser. A solution to this is building multiple ground stations, which are telescopes on Earth that receive infrared waves. If it’s cloudy at one station, the waves can be redirected to a different ground station. With more ground stations, the network can be more flexible during bad weather. SCaN is also investigating multiple approaches, like Delay/Disruption Tolerant Networking and satellite arrays to help deal with challenges derived from atmospheric means."

https://www.nasa.gov/technology/space-comms/optical-communic...

Some more info on Optical Communications for Satellites: https://www.kiss.caltech.edu/workshops/optcomm/presentations...

So it'll never work in Scotland.

9600 Baud...

CONNECT 9600

Seems like reusing some of Star Wars research could be used as well where the beam is constantly adjusted with independent mirrors to keep the beam coherent through the atmosphere. Also learned was the beam itself starts to distort the atmosphere requiring even more adjustments.

Wouldn't the angle of the offset matter? It seems like it would make scattering worse to be off-axis by too far.

Which then also means you have to build ground stations in this range yet far enough apart that they experience different weather yet close enough that you can redundantly link all the sites.

Aside from government and massive telecommunications companies who would this serve?

???

It's just really cool sci-fi tech that I want to see used in something other than DLP chips!

JWST and other observatories with segmented primary mirrors kind of use the segment alignment one time to get the correct alignment once. Then there is Adaptive Optics. It's kind of the opposite direction though as they are using a laser to detect the distortion so it can be compensated in the image. From learning about SDI when I was a kid/teen, it's just always been about controlling the laser itself in my mind.

The JWST does not have to deal with atmosphere or weather and uses a giant sun shield to keep the internal temperature stable so these alignments have the longevity you need to make the platform work.

Yes, maybe my comment wasn't clear if you're thinking I thought JWST was using AO. It used segment control for alignment once.

>the beam itself starts to distort the atmosphere requiring even more adjustments.

may be something like this - a high-power impulse making a channel through whatever clouds, mist, dust and after that information carrying ray/impulse through the channel, rinse and repeat

Multiple ground stations are a fine solution for backhaul, but not most end-user use cases.

That 6 Tbps optical link is the max per MEO satellite and they are only planning 128 of those. I imagine the end users of that are pretty much only backhaul customers, individual households/businesses would still need RF or wireline service.

I think customer speeds is 144 and the 6Tb is their ground links to their stations. That is my take on it at least as its not super clear. I'm curious as to how it works as well.

My read was that they're going to have 144 Gbps RF for both regular users and their ground station gateways, and 6 Tbps optical for satellite-satellite back haul, but then you can also buy direct ground-MEO access to a back haul link. (Presumably MEO-only because it's hard to maintain the link to a fast-moving LEO satellite?)

They don't seem to mention using optical for their own ground stations - maybe too unreliable?

With both RF and optical you could see FEC or ARQ being used for something that isn't 100% signal loss. Downlink is optical, uplink is RF. Downlink transmits with FEC, user terminal fixes as many errors as possible, still missing packets so requests ARQ and either gets retransmission on optical or RF.

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