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Starlink's laser system is beaming 42 petabytes of data per day

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Re: Starlink's laser system is beaming 42 petabytes of data per day

#461

Post by edmundsauto »

mrb wrote: post #225

So that is "432 Mbit/s per laser, and 9000 lasers total". I don't know you guys but I find that statement much more relatable than "42 PB/day". Interestingly, they also say each laser "can sustain a 100Gbps connection per link" (although another part of the article even claims 200 Gbit/s). That means each laser is grossly underused on average, at 0.432% of its maximum capacity. Which makes sense since 100 Gbit/s is p…

The average household probably watches significantly more tv than HN users. That is almost all streamed - something like 6 hours per day times multiple TVs.

1tb feels reasonable to push that much video.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#462

Post by NelsonMinar »

quailfarmer wrote: post #373
NelsonMinar wrote: post #131

Earlier quoted context omitted.

I think it means pretty much all Starlink users have at least some data go over laser links every two hours. Which is a bit of surprise to me, if true. I have a year or so of fine-grained latency detail taken with IRTT on a Starlink connection, I should sit down and see if I can see times I'm using a satellite. Latency is highly variable in Starlink though so it's pretty noisy data.

Hey, I’m very curious if you’ve seen any improvement in latency over the past month.

not in the last month but I had a major improvement 11 months ago. still not clear what they did, but best guess is shifting load.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#463

Post by ang_cire »

colordrops wrote: post #331
edude03 wrote: post #292

Earlier quoted context omitted.

_actively_ watch? Probably not many. Having it on as background noise however? 5 hours is pretty easy

Is that still a thing with young people? I associate leaving the TV on in the background as an older generation thing.

sure, it's just Critical Role playing on the YT app on their tv, rather than some cable channel.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#464

Post by ang_cire »

jimmy76615 wrote: post #417
dr_dshiv wrote: post #351

Earlier quoted context omitted.

John Von Neumann liked to do math with the TV on as background noise. Genius.

I heard all those stories about Von Neumann working like that. According to a biography, his wife once designated a room as his office and he became very angry about that since it was too quiet for him to work there. Personally I need almost complete silence in order to get anything done, his abilities in this regard always fascinated me.

I actually prefer to work in a cafe setting, where there is a good amount of non-directed background noise; no one talking to me, but just to each other.

If it's dead quiet, I become hyper-alert to noises, to the point I can't concentrate on working.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#465

Post by mlindner »

7e wrote: post #129
Scoundreller wrote: post #23

So which points are getting “faster than fibre” latency because of this? Extra distance up and down, but make up for it on the long-haul. Won’t beat HF radio though.

Starlink adds a latency penalty of tens of milliseconds going through the atmosphere. Each round trip is four hops through the clouds. I expect most of this delay is forward error correction, combined with lower bandwidth of the radios. On top of that, you may have queuing in each satellite. Finally, the satellite laser links aren’t pointing exactly in the direction you want to your packets to travel. They’re at some…

This is just incorrect. The speed of light through atmosphere is almost identical to speed of light in a vacuum. There's no latency penalty for traveling through the atmosphere. The one-way time delay to a Starlink satellite is about 2 milliseconds.

Re: Starlink's laser system is beaming 42 petabytes of data per day

#466

Post by themeiguoren »

qayxc wrote: post #424
mlindner wrote: post #329

Earlier quoted context omitted.

Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location. However instead the satellites are designed to be intentionally "demisable" meaning that every portion of the satellite should vaporize/turn to char/dust during re-entry. Put another way, every kilogram of Starlink spacecraft has as…

> Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location. SpaceX says otherwise, see [1] SpaceX spokesman James Gleeson, when asked about the 10 satellites, said SpaceX is “performing a controlled de-orbit of several first iteration Starlink satellites,” using onboard propulsion. There's…

Not quite. The spokesman is a talking about controlled deorbit, where propulsion is used to actively lower altitude rather than coasting down due to atmospheric drag. This is in contrast to controlled reentry, which targets an ellipse on the ground where any debris would fall. The latter requires either much more thrust than their electric thrusters have, or a much steeper reentry angle than Starlink's circular orbits.

Starlink satellites are pretty well aerodynamically balanced when in their "ducked" orientation, but are not going to be able to overcome aerodynamic torques below 200 km or so, meaning they will be unable to point their thrusters in target directions. At that point, there are still 1-2 days before reentry will occur. Hour-to-hour variability in tropospheric atmospheric density due to solar flux levels and geomagnetic activity means that the precise reentry time will be unpredictable to within a few hours (which equates to anywhere along the ground track of a few orbits).

Re: Starlink's laser system is beaming 42 petabytes of data per day

#467

Post by themeiguoren »

mschuster91 wrote: post #6

> The lasers, which can sustain a 100Gbps connection per link > Brashears also said Starlink’s laser system was able to connect two satellites over 5,400 kilometers (3,355 miles) apart. The link was so long “it cut down through the atmosphere, all the way down to 30 kilometers above the surface of the Earth,” he said, before the connection broke. How do these tiny satellites achieve this kind of accuracy and link qua…

This says more about the link budget than anything else, it's much harder to keep tracking when satellites are close to each other moving at high relative velocities. At the distances in your example, movement of the laser link optical head is very slow, on the order of 0.01 - 0.1 deg/s. Optical heads also have a control loop which actively corrects for pointing errors once a positive link is established. Check out: https://www.sda.mil/wp-content/uploads/2022/04/SDA-OCT-Stand...

Re: Starlink's laser system is beaming 42 petabytes of data per day

#468

Post by inemesitaffia »

p_l wrote: post #460
inemesitaffia wrote: post #459

Earlier quoted context omitted.

Launch customer yes. Investor no. That's Google and Fidelity Paying above the regular rate. Definitely

USAF fronted significant (40%? Those kinds of numbers were floating around) of initial operational capability costs.

I'd like to see an article or even an estimate. SpaceX spent 2.4 billion upfront on the dishes alone to ST Micro.

I don't believe the AF spent anything more than 100m for whatever R&D program. And the money was post development.

Was it a black budget thing?

Re: Starlink's laser system is beaming 42 petabytes of data per day

#469

Post by schiffern »

Gravityloss wrote: post #454
schiffern wrote: post #269

Earlier quoted context omitted.

>these laser links are used in bursts and the link stays established only for a few tens of seconds or minutes, until the satellites move away The way Starlink satellites are in orbit, the same satellites will remain "ahead" and "behind" you in the orbital plane. Those laser links (specifically!) will remain relatively persistent. This arrangement is similar to Iridium FYI. FTA: "in some cases, the links can also be…

Partially! There are also ascending and descending satellites meeting. Ascending and descending doesn't mean altitude but in a "2D view" sense. See https://www.heavens-above.com/StarLink.aspx

Thanks, this is an important point. I missed the fact that Starlink's orbital planes actually cover the full 360° of RAAN[0], not just 180° like Iridium did (presumably to minimize the number of satellites).

So actually this Iridium-type "seam" disappears, meaning that every satellite should always have co-orbiting "neighbors" on both sides. Cool!

[0] https://en.wikipedia.org/wiki/Right_ascension_of_the_ascendi...

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