NASA does know that the ISS spins around the earth and isn't in line of sight all the time? Is the geostationary 'base station' going to have a stonking big buffer because watching Netflix in space will be tedious - watching for 10 minutes, buffering for 90, watching for 10, buffering for 90.
NASA to fire 1Gbps laser 'Wi-Fi' ... into spaaaaace
NASA hopes to use lasers to shoot data to and from the International Space Station and Earth at gigabit-per-second rates by 2021. The Laser Communications Relay Demonstration (LCRD) has the potential to become “the high-speed internet of the sky,” the American space agency said on Wednesday. The plan is to encode digital data …
COMMENTS
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Thursday 23rd March 2017 06:27 GMT Anonymous Coward
They'll only need two
If they have two of these satellites on opposite sides of the globe one will always be within reach of ISS. That probably makes more sense than having ISS go directly to Earth through the atmosphere.
And even with one, good bandwidth 50% of the time is still an improvement.
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Thursday 23rd March 2017 20:42 GMT tom dial
Re: Latency...
I make it around 120 milliseconds one way transit to a geosynchronous satellite, so about a quarter second to the ultimate destination (plus additional switching time within the routing station, and around half a second turnaround. Short enough for voice communication but long enough to be quite annoying on an interactive terminal or the like.
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Friday 24th March 2017 02:48 GMT Oengus
Re: Latency...
120 milliseconds from earth to geosynchronous satellite, depending on location of location of space station receiving message 120 milliseconds (low earth orbit) to 240 milliseconds (geosynchronous orbit on the opposite side of the earth) or more if space station is at L4 or L5. Then of course you have to double that for the return trip...
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Friday 24th March 2017 00:14 GMT bombastic bob
Re: Latency...
latency goes up when you use geosync satellites. best sync would be to multiple ground stations underneath the expected path of the ISS, almost like cell towers [with frickin' laser beams, OK couldn't resist either, heh]
really, though, a design of a laser with less than a 1 degree cone might do the trick, then have the response laser modulate the original "carrier" [i.e. reflect it back with interferometry involved, let's say]. targeting a laser within one degree shouldn't be too hard. existing weapons systems might already have similar capability...
whole point would be for the ground-based laser not only to send data, but to power up the received signal as well. A laser has a cone-shaped propagation pattern, more or less, and so disperses a little bit [especially from atmospheric interference]. Then it's just reflected back with modulation by the I.S.S..
yeah, it could work... (with frickin' laser beams)
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Thursday 23rd March 2017 09:59 GMT Pen-y-gors
Another slight issue?
The article says it needs to be very precisely aligned. So, even if you get over the issue of line-of-sight from a network of base stations, doesn't that mean that you'll need a separate ground-based laser + tracking/aiming hardware for each space vehicle you want to talk to?
Not a major problem at the moment, but does rather limit options for expanding the system.
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Thursday 23rd March 2017 11:16 GMT Pen-y-gors
Re: Another slight issue?
I wondered about that. Point the ground laser at a 'router' satellite in geostationary orbit, but then the satellite needs a separate laser rig to pass the data on to each space vehicle, which won't be in geostationary orbits and could have much larger angular velocities relative to the satellite than for the ground ones. And that kit could be quite heavy. Probably cheaper to do it directly from the ground, but still not easily expandable.
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Friday 24th March 2017 09:29 GMT Francis Boyle
Re: Another slight issue?
The article is talking about a test system which will be on a satellite in geosynchronous orbit (presumably because actually creating the tracking tech is still on the to do list). The business about routing is purely commenter speculation. My take is that they are planning to do direct to LEO from a series of ground stations but that too is pure speculation.
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Thursday 23rd March 2017 12:37 GMT Brangdon
SpaceX
This sounds like the technology SpaceX plans to use for their Internet via satellite scheme, which they hope will pay for their Mars colony. The hard part (aside from launching 7,500 satellites into LEO, which they think they have nailed), is making the pizza-box ground transcievers that can track the satellites as they move.
https://en.wikipedia.org/wiki/SpaceX_satellite_constellation
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Thursday 23rd March 2017 14:30 GMT DropBear
Re: "requires the optical modules to be perfectly aligned"
The neat thing about optics is that we're pretty good at shaping the beam width to an almost arbitrary size at the destination. Not to say that kilometer-wide beams are a bright idea, but you don't exactly need to hit a coin with another coin...
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