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

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 probably achievable in ideal situations (eg. 2 satellites very close to each other), so 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 and no longer are within line of sight of each other.

And with 2.3M customers, that's an average 1.7 Mbit/s per customer, or 550 GB per customer per month, which is kinda high. The average American internet user probably consumes less than 100 GB/month. (HN readers are probably outliers; I consume about 1 TB/month).

Netflix uses 3-7GB an hour. The average person is spending 4-5hrs a day watching TV. I’d say most are above 100GB/month.

But that’s me.

Who has 4-5 hrs a day to watch television? ..or am I completely out of touch?

_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.

I'm middle aged. This kind of background noise sounds terrible to me.

Maybe I just grew up in a quiet place.

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.

Same and same and same, but I know exactly why I won't leave the telly on - I'm very susceptible. It grabs me. Even though I have no interest in ads or even 95% of programming. It's not a pleasant feeling.

I grew up being accustomed to having the TV as background noise but stopped watching it when I moved out. Now, when I visit my parents, it's honestly quite difficult for me to focus on conversation - there's a machine in the corner making deliberately attention-grabbing sights and sounds. So I think your experience is normal & I empathise with the generation that complained about TV ruining family life.

When you have permanent background noise in the form of Tinnitus already it's an improvement.

It is terrible, yet quite some people rather have that distracting noise, than hear their own thoughts.

For some it is just the illusion of having more people around them, though.

There are people who like to hear other humans blathering on all around them. Then there are sane people.

We're outnumbered.

If Millennial still = young then yeah, YT or something in background on TV, doing something on laptop (dev, or photo editing or other) and then occasionally phone over laptop as well to reply to chats and stuff.

I would kill for some decent high res wide fov AR glasses.

Millennials are currently in their late 20s to early 40s.

I mean I use youtube lets plays or twitch streams for that, but yes its still a thing.

It's a normie thing coping with unbearable ringing emptiness of mind. My sister and niece (7yo) do it.

watch, or leave running as background noise …

Any recommendations for shows that make good background noise? I wish they had more concerts.

For me it depends on what I'm doing. During working hours I have Soma FM playing at a low volume. Otherwise I'll probably have cooking videos or history documentaries playing as the background noise.

the ones i see most often are: The Office, Futurama, Simpsons, Friends, Brooklyn 99, How It's Made (my favourite)

kids these days mostly use youtube or twitch for background noise i think

Happy british baking children! I dont know what its called but it is on netflix and they are indeed happy, british and they bake. Or just put on Asianometry if you need to focus a bit more. I must have been through his back log a dozen times at this point. There is something about that mans voice that helps relax and focus like nothing else

Shouldn't audio (radio) suffice for that?

"What's a radio?" the kids ask.

According to historical Nielsen data[1] from 1991 to 2009: most Americans.

Even back to 1950, for per household data, it was above 4 hours.

[1] https://www.nielsen.com/insights/2009/average-tv-viewing-for...

Thats per household, not per person. That's different. And households also tended to get smaller.

The 1991 data and on was 4+ hours per person (older than 2). 7-8 hours per household.

They didn't have per person for the 1950 to 1990 data, only household (pdf in the link).

Children, sadly.

Families sharing an internet connection. Kids watch 1 o 2 hours each, mom and dad another hour each.

Yep, but that data originates from the providers network and never leave the providers network, so they probably don't count it towards your usage the same way.

I don't think that breaks net neutrality either, which the FCC seems to be reimplementing

Edit: see https://openconnect.netflix.com/en/

This obviously has no relevance for starlink which does not have local datacenters for cdn purposes. All that bandwidth is going through the satellites right before it reaches the user.

I wouldn't be surprised if starlink doesn't at least experiment with making the satellites a big bunch of CDN nodes.

Imagine they put 10TB of flash memory on the satellites and run virtual machines for the big CDN companies (cloudflare, Google, Netflix etc).

I reckon that 10TB is still big enough to service a good little chunk of internet traffic.

I guess the problem is that most of the useful bits of that 10 TB are going to be most of the time somewhere far away from the target audience.

You have to share that 10 TB with everything on that satellite's orbit.

Definitely sounds like a no-brainer / reasonable next step.

Most ISPs have CND appliances in their racks to save on uplink bandwidth. And from a satellite perspective the uplink (in this scenario: the downlink from the satellite to the gateway) definitely is the expensive bottleneck.

You want to avoid congestion and every bit of caching could be helpful.

Then it comes down to the mass and power budget (and the reliability of flash drives in space) - but that doesn't seem too terrible.

All my data usage is over LTE and NR. On one line it mostly gets used for streaming video (YouTube,plex,twitch) and averages around 500GB/mo. I rent a line to a friend and he's doing over 10TB/mo on mostly machine learning stuff and astronomy data.

T-Mobile absolutely counts all data used over the network, my voice lines go QCI 9 (they are normally QCI 6) when over 50GB of any kind of data usage each month, the home internet lines are always QCI 9. I don't have congestion in my area so it does not affect my speeds. This is QoS prioritization that happens at physical sector level on the tower(s).

They absolutely count it the same way. Comcast just gives me a number for bytes used, with a limit of (IIRC) 1.2TB above which they start metering. Our family of four comes dances around hitting that basically every month. The biggest consumer actually isn't video, is my teenage gamer's propensity for huge game downloads (also giant mod packs that then break his setup and force reinstall of the original content).

I think a few hundred GB for a typical cord-cut household is about right.

Do you have a source on the 4-5 hrs?

https://www.statista.com/statistics/420791/daily-video-conte...

300+ minutes a day for TV + vMOD (streaming services). Since no one actually watches TV anymore, at least not through traditional TV, I summed them.

I think the average Instagram or TikTok user must be using more than 100GB/month. And if you count YouTube and Netflix, it's probably more than that.

Is resolution going to peak? Like speeding on a highway are there diminishing returns? On the other hand, bandwidth availability seems to also drive demand...

Is resolution going to peak?

It should. At some point you are beyond any difference a human eye can detect on a tv or monitor you’re sitting less than 10ft away from.

It probably won’t though because capitalism means there has to be a reason to sell you a new widget and 3D was an utter failure.

Is resolution going to peak?

not for awhile. apple vision / oculus will stream (4k/8k) 3d movies.

https://developer.apple.com/streaming/examples/

Two things:

Resolution is always determined by angular resolution at viewing distance, even for analog TVs(they were smaller and further away), and also,

Videos on Internet is always heavily compressed - the "resolution" is just the output size passed to the decoder and inverse of minimal pattern size recorded within, technically not related to data size. Raw video is h * v * bpp and have always been like low to dozen Gbps.

Just my bets, the bandiwth may peak or see a plateau, but resolution could continue to grow as needed for e.g. digital signage video walls that wraps around buildings.

Sure, but "4k" is still being used as a differentiator for streaming companies in how much they charge. Even then they serve up some pretty compressed streams where there's room to do less of that for a noticeable notch in quality.

There's of course a limit. The "native" bitrate equivalent of your retina isn't infinite.

Next step though is going to be lightfield displays (each "pixel" is actually a tiny display with a lens that produces "real" 3D images) and I assume that will be a thing, we shall see if it does better than the last generation of 3D TVs/movies/etc. That's a big bump in bitrate.

There's also bitrate for things like game/general computing screen streaming where you need lots of overhead to make the latency work, you can't buffer several seconds of that.

The next gen sci-fi of more integrated sensory experiences is certainly going to be a thing eventually too. Who knows how much information that will need.

When more bandwidth becomes available, new things become possible, sometimes that are hard to imagine before somebody gets bored and tries to figure it out.

When I'm futzing around with ML models, I'm loading tens of gigabytes from disk into memory. Eventually something like that and things orders of magnitude larger will probably be streamed over the network like nothing. PCIe 4.0 x16 is, what 32 GBps? Why not that over a network link for every device in the house in 10 years?

This is being downvoted but it's probably about right.

My smart TV used 483 GB in the last 30 days

Most customers aren't served by lasers, their data goes up to the satellite and down to the nearest gateway. Lasers serve customers out of range of a downlink gateway, and the traffic probably travels the minimum hops needed to get to one.

But with lasers, it makes sense to route your packets via space. For example traffic to a different continent would be faster (and cheaper) through space. Furthermore, I assume lasers have more capacity than gateways, so they could increase capacity of one satellite by bundling with more gateways.

I thought that Starlink always "landed" to a base station back in the same jurisdiction? I think relaying through space could open a regulatory can of worms.

What kind of worms?

All countries have strict regulations on radio waves, whether that's sending or receiving. The UK for example requires a license for base stations that stipulates things like geographical boundaries, etc.

You can't freely blast radio waves into a country without falling subject to its varying regulations, but the regulations for "pre Starlink" satellite broadband/phones/etc are fairly well established.

Well maybe it makes sense for US costumer to send their traffic down from Starlink in Canada and then via fiber to the USA? I do not really see the problem if the traffic is encrypted and forwarded.

Bypassing spying, geofencing and other regulatory stuff, perhaps? Also curious what the can of worms might be.

Unfortunately, the routing to make this feasible doesn’t exist yet. Users need a single IP address from a range that’s homed at a single PoP. Starlink doesn’t support user-user connections through the mesh, you need to go all the way out to your PoP, then over to the other users PoP, then back through Starlink to that user.

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 maintained for weeks at a time"

FTA: "in some cases, the links can also be maintained for weeks at a time"

I think there is a lot of variance. The article also states about 266,141 “laser acquisitions” per day, which, if every laser link stayed up for the exact same amount of time, with 9000 lasers, means the average link remains established for a little less than an hour: 9000 (lasers) / 266141 (daily acquisitions) * 24 * 60 = 49 minutes

So some links may stay established for weeks, but some only for a few minutes?

I would guess that the links between satellites on the same orbit stay for weeks, but the ones that cross between orbits have to constantly re-established.

Correct.

I believe Starlink (like Iridium) doesn't even try to establish connections "across the seam," ie the one place the satellites in the adjacent plane are coming head on at orbital speed.

This make side-linking easier because the relative velocity is comparatively low, but in general you unavoidably still need to switch side-link satellites (on one side) twice per orbit. Hence 49 minutes: this average must be calculated per connection not per second, so the front/back links (plus random noise) count less, so it only drags the average from 45 minutes up to 49 minutes.

I believe Starlink (like Iridium) doesn't even try to establish connections "across the seam," ie the one place the satellites in the adjacent plane are coming head on at orbital speed.

The slide showing the multiple possible paths traffic can take seems to disagree with this statement?

The first slide says "9000+", suggesting that the number of space lasers is slightly over 9000. I feel like that's an important distinction.

Most likely it's a reference to the "it's over 9000!" meme.

Data might get counted multiple times as it takes many laser hops to reach its destination.

Good point.

Just because they seem grossly underused, there are probably plenty of other non-ideal constraints like power usage for instance.

Thermal management is also a tremendous problem in space. All power generated must be radiated away, and satellites effectively sit inside a vacuum insulator.

I'd be interested in what the sustained power/thermal budget of the satellites is.

That means each laser is grossly underused on average, at 0.432% of its maximum capacity. Which makes sense since 100 Gbit/s is probably achievable in ideal situations (eg. 2 satellites very close to each other), so 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 and no longer are within line of sight of each other.

I think I agree that each laser is grossly underused on average, but if you read the article, there's quotes about the uptime of these links. They're definitely not just "used in bursts [of] a few tens of seconds or minutes".

Yeah 1TB seems average for anyone in IT who is really into data.

I'm kinda pissed their is no local ISP competition in my area....and iv tried reaching out to companies with little success...or they say were expanding to your area soon but will not say when.

10GB symmetric fiber isn't hard. Hell I'd use more bandwidth if I could but I'm stuck with no fiber atm

That means each laser is grossly underused on average, at 0.432% of its maximum capacity.

Don't forget that every communication protocol has fixed and variable overhead.

The first is a function of the packet structure. It can be calculated by simply dividing the payload capacity of a packet by the total number of bits transmitted for that same packet.

Variable overhead is more complex. It has to do with transactions, negotiations, retries, etc.

For example, while the theoretical overhead of TCP/IP is in the order of 5%, actual overhead could be as high as 20% under certain circumstances. In other words, 20% of the bits transmitted are not data payload but rather the cost of doing business.

My parents moved in and, being old, stream TV all day (instead of cable) and end up using about 40 GB per day with 1080p. We keep hitting our max of 1.2 TB set by our cable company (because there are others in the home!).

I should probably see if my router can bandwidth limit their mac addresses...

And with 2.3M customers, that's an average 1.7 Mbit/s per customer, or 550 GB per customer per month, which is kinda high. The average American internet user probably consumes less than 100 GB/month.

Dead internet theory (alive and well!)

There’s probably redundancy in the links. In other words, A sends a MB to B which sends it to C, that’s 1 MB of information transmitted to customers but 2 MB of laser transmission.

I’d have guessed they count “delivered bytes” not “transmitted bytes” and then you need to take into account each leg of the transfer. Which for starlink is at least two (for the simple bend pipe situation) and up to potentially something like ?20? (for a “halfway around the globe, totally starlink” connection). The latter is probably statistically negligible, but even the factor two would give ~2% utility. Which, taking into account, that at least 2/3 of the orbit time is spend out of reach of anywhere useful, this would give something like 1 in 10 possible bytes being transmitted. Which is much better than I’d have guessed if asked blindly

Where did you get that 100GB/mo number from? 4K streaming eats up data transfer quickly. Comcrap & friends knew what they were doing making arbitrary data caps that sounded like a big number at the time. Wireline data caps should be illegal.

There is one key issue of keeping lasers aligned for long durations between satellites and even between a satellite to a ground station. There are vibrations in satellites and even a tiny bit of that vibration translates to beam misalignment. Am not an expert though. That could explain the bursts.

So it's hard to sustain the theoretical 100GPS connection for hours let alone days across 2 end points which are in constant motion.

if you stream you use a lot more than 100gb/month. I use around 1tb with a family of 3.

"Customer" may refer to households, not individuals, in which case it could be numerous internet users soaking up data per customer.

i think even more relatable is how many customers they can handle at say 200 mbps

I sit in my hot tub at night and see 1-2+ satellites go over every single time I'm out there.

Which also makes me wonder how many of the shooting stars I've seen recently are just old starlinks burning up.

How do you spot a satellite? I've never seen one.

1. The satellite needs to be passing overhead at an angle where you can see it, and clear skies etc.

2. The sky needs to be dark enough to see it (so twilight or night)

3. The satellite needs to be illuminated by the sun.

4. The satellite needs to reflect enough light that you can see it.

Basically this happens just before sunrise, and just after sunset. So the ground and sky are dark (allowing you to see through the atmosphere), and the satellite - being at high altitude - is still illuminated.

As they pass overhead, you can often see them suddenly vanish as they pass into the Earth's shadow.

The International Space Station is a good one to find, as it's quite bright (very large).

There are various websites and apps; some phone apps use the GPS and magnetometer to show you what direction and time to look, and a search tool to look for visible objects at your location. It used to be really good with the old Iridium satellites, which gave a bright flash due to their large flat antennas.

Basically this happens just before sunrise, and just after sunset.

I've seen plenty of satellites in the middle of the night, from very dark areas (wilderness). They look like stars, only they move more quickly. These observations go back a decade, at least.

That doesn't seem right, why would they be bright?

They reflect sunlight for some period of the evening and morning, before the sun is shining where you are and illluminating the sky too much.

so not in the middle of the night.

That depends on the altitude. GPS satellites at 10000km can be lit up in the middle of the night. Starlink satellites at 500km can’t.

Ah yes, of course you're right. After all the moon is nothing but a satellite either.

Between when the sun first disappears below the horizon and when (nearly) all its light disappears, i.e., the end of astronomical twilight when the Sun's center is 18 deg below the horizon, seems to be about 90 minutes.

https://www.timeanddate.com/astronomy/different-types-twilig...

It's been awhile, but I'm pretty sure I've seen these much later than that. I'm talking about lying in a sleeping bag, looking up at the amazing starfields of pitch-black wilderness nights (tip: never use a tent except in extremis - look what you're missing!).

That's a very good question. I'm sure of what I've seen, many times over years:

I can tell you that they look like stars - so much that I need a reference point, an actual star or planet, to verify they are moving and not a 'stationary' star (judging movement being otherwise very difficult at that distance). They move very steadily, horizon to horizon, or as far as I can track them. A wild guess, based on memory, is one might take 5 or 10 minutes to cross between my horizons (usually I'm not on a plain - trees, hills, mountains may elevate my 'horizons' and reduce the distance).

Natural celestial object? No way a star is moving that fast relative to other stars and Earth's horizons. Asteroid? That seems hard to believe, due to size and illumination. Comet? Are there lots of tiny ones? I never see tails. Maybe a meteorite entering the atmosphere that doesn't yet have a tail?

Other human-made objects? Airplanes would look bigger and have colored, blinking lights - I've seen plenty of airplanes at night. Maybe there are higher flying airplanes without the colored and blinking lights? Are they illuminated whitish, and so far away they'd look like stars?

I've seen them so many times, I'm confident that I could take anyone to a wilderness area on a clear night and find one within 15-20 minutes, probably less.

A wild guess, based on memory, is one might take 5 or 10 minutes to cross between my horizons (usually I'm not on a plain - trees, hills, mountains may elevate my 'horizons' and reduce the distance).

Yup 5-10 minutes is right. It depends on the orbit altitude and the height of the pass.

You can use sat tracker apps to identify which one you're seeing. I do this sometimes because I'm a ham radio operator and I track the one I want to use sometimes with a directional antenna.

No way a star is moving that fast relative to other stars

No star moves relative to other stars when viewed from earth. They are all so far away they appear static. The starscape rotates as a whole (well it doesn't, the earth does, but to the observer it seems that way), but relative to each other they absolutely don't move.

If they do move, it is definitely a sign to stop drinking :) :)

Asteroid? That seems hard to believe, due to size and illumination.

Also asteroids move way faster across the sky than a satellite. And they're rare except during that time of the year when they're really common.

Comet? Are there lots of tiny ones? I never see tails.

Comets are incredibly rare in this galactic neighbourhood.

and Earth's horizons. Asteroid? That seems hard to believe, due to size and illumination. Comet? Are there lots of tiny ones? I never see tails.

Asteroid? That seems hard to believe, due to size and illumination.

And the distance - most asteroids pass by much further out than even the moon, so their motion would be hard to detect.

I grew up in a rural area, on a moonless night, without a fire, as well as giving your vision some time to adjust to the darkness, you can see crazy amounts of stars along the Milky Way plane.

I would guess, reflected moonlight (moon over the horizon) would be enough to light up the dot well enough to see unaided.

I was mostly referring to the brightest things like the ISS, Starlink and (formerly) Iridium satellites, which are in low Earth orbit.

Higher orbits are visible for longer, due to the angles involved: because they're so high, such satellites can remain illuminated with the Sun further below the horizon. The Moon is the most extreme example: it's almost never in Earth's shadow.

because they're so high, such satellites can remain illuminated with the Sun further below the horizon. The Moon is the most extreme example: it's almost never in Earth's shadow.

Very good point.

In short: after sunset.

I remember chasing one of the iridium flares and it was very bright, even during the day

To me, they look like little white dots moving across the sky. Brightness can change as they move too. It'll start off bright and then as it goes away it eventually disappears entirely. Since I usually sit in the same position in the hot tub, I've come to notice that I usually see one of them cross a pretty specific path from north to south, so I've gotten used to looking in that part of the sky as I'm sitting there. It happens so frequently, I get a little disappointed if I don't see one!

Planes are similar, but tend to have flashing or colored lights and obviously aren't as far away.

I'm in a big city, but close to the ocean so I have a bit less light pollution. The city is also heavy military, so that could be part of the frequency.

Update: if you're near any of the spacex launches, you can watch the rocket too. I'm house sitting in Irvine, CA and saw the Monday launch go right near the house. Amazing to watch the plume from the rocket!

I guess they disappear as they approach the horizon because the light is spread/absorbed too much by going through more atmosphere?

I actually see them disappear long before they get to the horizon. My guess is just less reflected light on whatever is shiny on the satellite.

that and/or entering the Earth penumbra.

In higschool we did an experiment with one of our science teachers based on this fact. We measured the duratuon of the iridum flares and could use some basic geometry to estimate how high their orbit is based on where the shadow of the earth is.

I don’t remember the details anymore, but it was one of the coolest practical experiments we did.

My impression was that you can only see them as they reflect sunlight in your direction. As the angle formed between you, the satellite and the sun changes, you will first not see the satellite, then see, then not see it again.

And of course, if it is 3am, and there is no sunlight at any altitude because the sun is on the other side of the world, no satellites are visible.

I could be wrong.

Just throwing this out there, but has anyone else seen 'formations' of satellites? I've only seen them once but there were about 5 to 10 (it was a while ago) of what I'm assuming are satellites moving in a line formation at high speeds across the night sky. They're too distant and too fast to be planes so I'm assuming they are some sort of military formation of satellites?

That's often a recently launched StarLink formation -- the bunch up in a line when deployed, and have to be maneuvered over several weeks to spread out and take different orbits.

I saw ISS in formation with visiting spacecraft a couple times - once with Space Shuttle back in the day and at least once with Dragon. Looks pretty interesting. :)

They're too distant

I don’t know how you would know that. People are very bad at seeing distances at these scales.

If they were indeed satelites they could be starlink satelites. They are put into orbit as a bunch together and then they spread along their orbital path as they take up their position.

This article has a picture, maybe you can check if it is similar to what you have seen? https://earthsky.org/space/spacex-starlink-satellites-explai...

If you could recall more details then maybe we can figure out more exactly what this might have been. (Such as where you were, which direction you were looking at, when did this happen, how fast did they cross the sky and how far the dots were from each other. Were the line spread in the direction they were moving or sideways?)

The Starlink ones look like Santa's sleigh https://i.imgur.com/4S0vbfY.gif

Only directly after deployment, though.

Nice image. The Starlink V2 are bigger though, so fewer per launch (~15 vs ~60).

I can guarantee you you have.

You probably just thought it was a star or a plane. They move but relatively slowly (even a fast LEO sat will cover the sky in about 5 minutes). They look just like a star apart from moving slowly. Depending on angles they can look pretty dim, especially the latest SpaceX sats. But the ISS is usually really bright because it's so huge and technically it's also a satellite.

You can tell them apart from a plane because they don't flash.

Edit: But yes there are several conditions that need to be met to see them like the other posters have mentioned. But every clear night near dusk or dawn you will see sats for sure. There are just so damn many in LEO now.

Some satellites do appear to flash because they are tumbling: https://www.satobs.org/tumble/tumbleintro.html

The flashing of satellites will generally be gentler than the short burst strobing of an aircraft.

The easiest satellite to see is the ISS. NASA provides times when it can be seen from any given place. I subscribe to the SpotTheStation mailing list.

In general, you can see a satellite when it is overhead and illuminated by the sun. In the evening, it will appear in the west, moving towards the east ( almost all satellites go this way, not just ISS ). As it goes farther east, heading towards darkness, it will fade away. The ISS is bright enough to see a reddish tinge as it passes through sunset light.

Shooting stars go much faster than satellites.

Yeah. With Starlink satellites, you need a lot of luck with the conditions to see them. I've seen them a handful of times and I'm in a relatively dark sky location.

ISS is often visible in the middle of the day even in bright midday Southwest sun, if you know where & when to look.

It depends where you live certainly - if you live close to a big city you will probably never see them. But there are places - like New Zealand - where you can see them fairly often. There are some online trackers you can use.

I live 10 miles from Boston and I've seen them a whole bunch. I've used https://james.darpinian.com/satellites/?special=starlink

It's usually a somewhat like a fast moving little but visible star. Fast as in it would usually cross 1/4 of the visible sky within 20 seconds or so.

You should try to find one once, with the help of an app. It's not that difficult.

If the seeing is good it's actually possible to spot up hundred satellites with the unaided eye. Due to light pollution, it's unlikely to spot one in most places, though. The ISS at least should be easily visible due to its size, even in places that aren't particularly dark.

My tip is that the very central part of your field of view has worse night vision than the rest (trading off for higher resolution instead), so if you spot something moving in your peripheral vision, don’t try to look straight at it or it’ll disappear; instead, look slightly to the side, and it’ll be easier to see (although maybe blurrier).

It takes several minutes for your eyesight to adjust enough to spot them with the naked eye. You can use websites to know when one is likely to pass overhead. Choose a suitable time (see: everyone else, basically right after dusk), and then lie down and stare up about 15-minutes ahead. Mushrooms are optional, they increase the chances of seeing something but decrease the chance that what you saw was real.

Probably out in a rural area far enough away from a major city its easier to see them.

Even in a city you stand a chance if you've got high walls around you. A courtyard garden for example. Just lie back and stare up.

https://james.darpinian.com/satellites/ Put in your location and it will tell you when and where to look at the sky to see one. Works great for me and hopefully it will work for you.

Which also makes me wonder how many of the shooting stars I've seen recently are just old starlinks burning up.

Probably close to none. The lifetime of the satellites is about 5 years give or take. According to this page [1], a total of 355 satellites have deorbited over the past roughly 5 years. That's an average of about 71 per year or about one every 5 days.

Since planned disposals are done over uninhabited areas (e.g. the pacific ocean), the likelihood of spotting one is very low.

Hope that helps answer your question, even it wasn't necessarily meant seriously :)

    [1] https://starlinkinsider.com/starlink-launch-statistics/

If someone makes a mistake and the satellite deorbits in the wrong place, am I likely to be impaled by a satellite screw or something travelling at terminal velocity?

No, they burn up. You can think of how much work goes into the heat shields on spacecraft that are supposed to survive reentry. Satellites have none of that.

I also think a screw at terminal velocity might not be particularly dangerous, similar to the popular "will a penny dropped off the empire skyscraper kill you?" question.

...which I suppose is closely related. The deorbiting satellite burns up because all that potential energy goes into heat because of the ~friction~ [edit: compression, thanks for the correction] that limits it to that low terminal velocity.

Heat is Not because of friction but compression of air

Starlinks are actually built so that nothing sizeable remains at all after reentry. This even delayed the laser coms a bit, as the original laser mirrors were too sturdy & so pieces of them could theoretically make it through.

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 much energy "stored" in it's motion as around 4-5 tons of TNT.

You mean 4-5 kg of TNT. Starlink is not relativistic yet.

China is still working on those reusable rockets...

https://www.youtube.com/watch?v=sDufpRp57ok

The lifetime of the satellites is about 5 years give or take. According to this page [1], a total of 355 satellites have deorbited over the past roughly 5 years.

Wow ... is it economical to replace the entire constellation every 5 years? How does the business side work? Or is it just a great money-burning party?

This is a large part of why they're pushing so hard on Starship. Falcon 9 is great and wildly economical, but it's not enough to make Starlink profitable in the long term. They need Starship to make that happen.

They also want to make Starlink satellites bigger, which also requires Starship's much larger diameter.

No, I love this data! Thank you.

The first time I saw the long line of starlink satellites in a dark rural area it was unreal. Straight up looked like aliens invading.

There are so many that I spot them with my telescope while watching the sky with some frequency. In the last year I've probably caught 6 or so. It's just a spot of light passing through the view, nothing spectacular, but I think it would have been virtually impossible 20 years ago.

As someone who also spends a decent amount of time outside at night, do you also see a ton of shooting stars?

I see them 1/3 of the time in outside for 30 minutes or more I’d say. Thought they were much rarer. Only seems a Starlinkn train once.

My understanding of the state of the art of inter-satellite optical links is that they have only been used between satellites that are basically in the same orbital plane and in more or less the same orbit. That is, the angle from one satellite to the other changes very very slowly, so that the optics don't have to do much tracking -- and consequently satellites can only form an optical link with other satellites that are ahead or behind themselves in ~ the same orbit.

Cross-plane optical links would have a trickier tracking problem.

While there's no explicit mention of same-plane vs cross-plane optical links, I assume that the first time people have a public cross-plane optical link, they will make a big deal out of it. :)

The article also mentions that SpaceX would need to do further study before using laser links between satellites and ground stations-- this kind of optical link would require both more angular tracking and probably atmospheric correction as well.

Take a look at the slides from the presentation, I think the geometry clearly shows cross-plane links in the mesh. Having worked on these types of systems, I've had more difficulty with the lookahead angles (rx from where the target was, tx to where it will be due to speed of light) than the tracking -- fine tracking performance was required for all modes, and it largely became a GNC and acquisition time issue (since they're ephemeral) for the cross-plane links.

In general, how is the initial alignment performed?

Is there rough pointing, followed by some rastering, until the sensor gets a hit? Maybe with some slight beam widening first? My assumption is that you would want exactly one laser, one sensor module, and probably a fixed lens on each? Is the sensor something like a 2x2 array, or pie with three pieces, to allow alignment? Or is it one big sensor that uses perturb and observe type approach to find the middle?

Also, is there anything special about the wavelengths selected? Are the lasers fit to one of the Fraunhofer lines? 760nm seems like a good choice?

A laser that transmits data at 100Gbps can also transmit at 1 bit per second with an additional path loss of 110 decibels.

You'd normally achieve this by transmitting a well-known pseudorandom sequence. You also need clock stability into the ppb range.

A path loss of 110 decibels is huge. It can easily account for your lenses being hugely off axis.

What books or webpages do I read to learn how to understand the why of your first sentence?

This is from the Shannon-Hartley theorem, the 'power limited case':

https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theore...

Alas there is no 'in general'. Acquisition is often the secret sauce due to, among other challenges, the extremely tight alignment requirement -- thermal shifts, satellite wobbling, etc, are all critical to manage.

On wavelengths, if you're trying to hit 100gbit+, you're probably having to use coherent optics, and there aren't many technology options or wavelengths on the market.

You got it exactly right! I worked on a simulation model of the complete optical setup of a laser terminal with movable mirrors and all including the fricking servo motors and a simple orbital model for the relative satellite positions. Plus an interface to drop in the actual acquisition and tracking code used on the embedded control system. All of that just to be able to do reasonably realistic simulations for verification and tuning of the secret sauce.

There's an interesting paper on the subject of alignment here. https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4...

GNC?

Guidance, navigation and control

Guidance navigation and/or control

The "routing in the mesh" slide? Definitely given where the satellites are in that picture some of the links would have to be cross-plane, it's just the whole thing looked so messy (even with it being geo-referenced on a globe) that I didn't know whether to consider it a "real routing example" vs a "notional routing example that we overlaid on the globe".

Sounds very cool that cross-plane links are doable, even if they have predictable complications compared to in-plane.

I would have thought that someone would make a big deal (have a press release, e.g.) out of successfully establishing cross-plane links, but maybe it just doesn't seem that impressive to people who already have good enough precise predictive ephemerides or satellite states to make those links in the first place.

Tracking is an issue, but doppler can also be a thing. At orbital speed (actually up to 2x orbital speeds) the doppler effect between two satellites can change the frequency enough to cause interference. Moving a scope to track a moving target is one problem, allowing the algorithms to adapt at the frequency shifts on the fly another.

Indeed Iridium had to deal with the same thing (or I guess, didn’t):

“ Cross-seam inter-satellite link hand-offs would have to happen very rapidly and cope with large Doppler shifts; therefore, Iridium supports inter-satellite links only between satellites orbiting in the same direction.”

https://en.m.wikipedia.org/wiki/Iridium_satellite_constellat...

Don't all satellites orbit in the same direction? Launching retrograde is just throwing away free velocity.

In the context of the full article (https://en.wikipedia.org/wiki/Iridium_satellite_constellatio...), it's clear they're talking about the polar orbits used by the Iridium constellation, which have "seams" around the Atlantic and the Pacific as the "first" set of satellites passing north-to-south overlap with the "last" set of satellites coming back south-to-north on the other side of their orbits. So of the 6 orbital planes used by the Iridium satellites, each plane covers 1/12th of the globe for each "half" of its over-the-poles orbit. So there are two "seams" where handoff is not supported, one off the eastern seaboard and one roughly over Japan.

There's an animation on linked article that explains this pretty well: https://upload.wikimedia.org/wikipedia/commons/thumb/9/90/Ir...

Ah I didn't realize they have all of their stats in polar orbits, that's interesting. Starlink is mostly equatorial afaik, the higher latitudes aren't very well covered.

Most of Starlink's orbits have an inclination of 53 degrees, which I wouldn't really call equatorial anymore.

The Iridium satellites are in what you might call "parallel" orbits, if you stretch the meaning of the word a little bit.

The wikipedia link above explains it well:

""" Orbital velocity of the satellites is approximately 27,000 km/h (17,000 mph). Satellites communicate with neighboring satellites via Ka band inter-satellite links. Each satellite can have four inter-satellite links: one each to neighbors fore and aft in the same orbital plane, and one each to satellites in neighboring planes to either side. The satellites orbit from pole to same pole with an orbital period of roughly 100 minutes.[8] This design means that there is excellent satellite visibility and service coverage especially at the North and South poles. The over-the-pole orbital design produces "seams" where satellites in counter-rotating planes next to one another are traveling in opposite directions. Cross-seam inter-satellite link hand-offs would have to happen very rapidly and cope with large Doppler shifts; therefore, Iridium supports inter-satellite links only between satellites orbiting in the same direction. """

The 'seams' have interesting implications for latency when I was working on Global Data Broadcast.

There were some experiments with communicating over Iridium to small cube-like sats back in the day, but we couldn't make the system on a chip beefy enough to do the Doppler shift calculations on the fly and survive a launch; it was close though. I think its possible to do now.

Doppler is not a big problem with lasers because the carrier frequency is so much higher than RF that it doesn't matter; it's bang-bang AM modulated.

I'm assuming two things: That something like Manchester coding is being used so that some clock skew is tolerable, and that the laser carrier is not in fact being frequency or phase modulated. Last I checked FM and PM of optical frequencies was not yet practical outside of laboratories, but I'm happy to be corrected.

Links between satellites closing range near 2x orbital speed have two problems: - bigger doppler - the lifetime of the link is much shorter

“Another really fun fact is that we held a link all the way down to 122 kilometers while we were de-orbiting a satellite,” he said. “And we were able to downstream the video.”

For the future, SpaceX plans on expanding its laser system so that it can be ported and installed on third-party satellites. The company has also explored beaming the satellite lasers directly to terminals on the Earth’s surface to deliver data.

So what happens to the laser beam when there are clouds?

Interesting parallel to solar panels.

It would fall back to radio and/or other connections. The laser connection would probably be sold at a discount rate due to the variable level of service.

maybe it could route around the clouds via some other satellites

The lasers aren't used for ground-to-satellite comms. While they refer to some of them maintaining a link through the atmosphere, the lasers are intended for satellite-to-satellite communication way above the atmosphere.

There are some wavelengths that maintain decent signal quality through cloud cover, and even rainstorms. I cannot find the paper right now, but iirc Tightbeam (formerly from the Google sharks with lasers team, now spun out as Aalyria), demonstrated space to ground comms in adverse weather with negligible packet loss and something like 40% reduced bandwidth.

The customer terminals will likely never connect through lasers (because a laser can only point in one direction at a time), but moving the ground station uplink to a laser link sounds very beneficial.

Right. The Iridium network had communication between satellites in different orbital planes passing each other but that was a pretty unusual capability.

I wonder how iridium actually handles the tracking (or if it’s just slow enough and lack of attenuation in free space just lets them blast it).

And if they have zones where they don’t go to adjacent orbits, but instead go up or down within their orbit for the handover between orbits.

Supposedly they use steering, since the horizontal azimuth to adjacent-plane satellites varies from 0 to 65 degrees across an orbit: https://apps.dtic.mil/sti/tr/pdf/ADA348174.pdf

It doesn’t get into it too much on pages 14 and 15, but it indeed suggests that they probably exclusively use the “intra-orbital” links closer to the poles to get data to a satellite where the inter-orbital links are more practical.

I believe Iridium had way more downlinks than they used to pre-bankruptcy. I guess volume constraints were less of an issue, so ok to hop around more in space.

This has more details: https://fcc.report/IBFS/SAT-MOD-20131227-00148/1031348.pdf

Apparently it only happens above/below 68 degrees latitude, so the next satellite with a working inter-orbital-plane connection is at most one hop ahead or behind.

https://spaceflight101.com/spacecraft/iridium-next/ has some more photos and diagrams; seems like they're really mechanically steered even on the NEXT constellation.

They do have counter rotating planes though, so there are places where two satellite tracks next to each other moving in opposite directions, and these pairs of satellites cannot use the cross plane communication mode.

Additionally, their inter satellite links use regular Ka band radio.

With 266,000 acquisitions per day, I suggest they are regularly doing links across orbital planes.

If they could only do in-plane links, they would have barely any acquisitions per day, because most links would stay up for long periods of time.

I'll assume there is a lot of double/triple (or higher) accounting going on here as data is sent through multiple relay hops to get the intended target.

Nah, I once did a job for a guy and they did LEO-GEO distances alright iirc and LEO-Earth in the mid-end 2000s, which has to deal with some pretty high angular velocities, if not as potentially high as LEO-LEO when they don't happen to be relatively nicely aligned. (In case that sounds strange, the guy was one of the two owners of a small, very specialized company that in turn was subcontracted by a rather bigger company. These laser terminals were quite the beasts and not really cheap.)

I have absolutely no idea how that number relates to any comparable operation. Can anyone add a banana for scale?

10 minutes of 4k video is ~30GB.

Knowing the size of a video file is exactly not the information, that would help me put this number in a meaningful perspective with any comparable operation.

How do I think of 42 petabytes in terms of an ISP? Is that a lot? How does it compare to other satellite providers? How does it compare to 4G capacities? Is this a small country worth of traffic or just any ol' data center? I have no intuition about traffic at this scale.

42 million gigabytes per day, or if we are working with 30GB for 10min of 4k movies - 233,000 hours of ultra HD movies per day

42 million gigabytes per second

Per day?

It's 42 PB per day, though.

per day*

Over estimating by a factor of 86,400.

I still dont think this is what the OP was asking for. This is in the context of an individual-HD video is an individual perspective. More helpful would be a comparison to say a small town or a major city or state.

Based on 2160p movies i've seen around the very largest max out at around 100, and 40 is more common, so this seems wrong.

We're not talking pirated movie here, think Netflix and Youtube.

Netflix and Youtube streams are less GB/hour than a typical movie rip. Roughly 3GB/hour at 720p and 8GB/hour at 4K. A decent-quality pirated 4K movie is more like 20GB/hour. A high-quality rip is 40GB/hour.

I feel like this is a bad example.

Most people's experience with 4K video is through a streaming service, and 10 minutes of 4K video on a streaming service is more like 1-1.5 GB.

Or a UHD Disc perhaps where 10 minutes is 3.5-7 GB.

If you took a petabyte's worth of 1GB flash drives and lined them up end to end, they would stretch over 92 football fields.

https://info.cobaltiron.com/blog/petabyte-how-much-informati...

That's actually a somewhat useful visual.

Not really unless you're using 1 GB flash drives from fifteen years ago. 256 GB is now common, which would make that petabyte less than 1 football field. (It's only 4096 such drives.)

You can buy a 1TB microSD card for $150 now.

What a time to be alive! Even those of us without a football field can lay out huge amounts of data in a straight line.

dang I can hear the youtube channel voice

...how large is a football field?

is it supposed to be actual football one or the field for handegg?

American Gridiron football, though Rugby League and Rugby Union (two other forms of football) use similar length fields/pitches. An Association Football pitch is almost always longer than a Gridiron field, depending on how you measure (it is typical to exclude the end-zones when measuring a Gridiron field, and while Rugby and Gridiron football have a playable area behind the goal (or try) line, Association Football does not.

As a side-note Canadian Gridiron football uses a longer field than American Gridiron football, though (measuring between the goal lines) still slightly shorter than a typical Association Football pitch.

Australian Rules Football is on a field typically longer even than an Association Football pitch, though I don't believe there is a regulation limiting the size.

Not really unless you're using 1 GB flash drives from fifteen years ago

1GB flash drives are still 1GB today.

256 GB is now common, which would make that petabyte less than 1 football field. (It's only 4096 such drives.)

If we're completely changing what we're using for scale, you can fit a petabyte on ~10 100TB drives, which is like 3% the length of an olympic swimming pool.

If you've got a laptop with a terrabyte drive, it would be 42,000 full laptops worth of data.

If you have a laptop with a petabyte drive, it would be 42 full laptops worth of data!

Might as well get a 42 petabyte drive.

Implementing a “comparable operation” to this satellite network using laptops instead is going to be really expensive fuel-wise, I think.

"Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway."

-- Andrew Tannenbaum

Bangladesh, the whole country, usage 2,300Gbps as of 2021. So 1 Petabyte per hour?

Edit: It's international traffic. YouTube, Facebook video has local cache server by ISP.

This is a useful scale of comparison and what I think OP was after

OP agrees

486GB/s

Better yet, a work in a 35 foot long Twinkie.

EMBL-EBI’s open transfer systems provide ~5PB of data each month.

ftp.ebi.ac.uk for example.

Assuming it's a constant data transfer rate, this is 3,889 Gbps. This is

- About 4,000 customers worth of maxed out Gigabit internet

- ~243,000 simultaneous Netflix 4K streams

- 1.6% the capacity of the latest BlueMed undersea fiber cable

According to a quick search the average US household is closing in on 600 GB of traffic per month, that makes 42 PB per day the internet traffic of 2.1 million households. Incidentally the second picture in the article says 2.3M+ customers. With an US average of 2.5 people per household that is the traffic of 5 million people or 1.5 % of the US population.

In the long run that could become a massive strategic advantage for the US. A 2nd layer of resilience over undersea cables

Real time video and telemetry for military drones that’s nearly immune to electronic warfare counter measures is the real end game. The fpv drone carnage in Ukraine is currently limited to the contact lines plus or minus a few kilometers. Satellite comms change that drastically. Yes it’s available now but highly restricted.

But not immune to missiles. Russia's already threatened to target Starlink satellites. Maybe they're bluffing, or not, but it does offer a reminder that these are just floating computers in the sky.

How feasible is it though once the network reaches a huge size? Starlink satellites are tiny, and they've been deploying thousands of them over the last few years. I imagine it would take enormous resources to shoot them down, especially if the US does treat them like a strategic resource and adds more for redundancy.

The huge size of the network is itself a risk. Kessler syndrome is something everyone is currently trying to avoid, but if you wanted to intentionally induce it you could just start launching giant payloads of tiny ball bearings into their orbits, or take down enough of them that the shrapnel becomes equivalent to that anyway. Starlink is low enough that the debris from even a full Kessler syndrome cascade will deorbit very rapidly, but we're still talking a 3-5 year timeframe, not months, and trying to rebuild capacity in that period will just worsen + extend the problem.

This is something commonly misunderstood. Kessler syndrome is a statistical process that happens over many years. It is not a sudden cascade like is seen in movies like Gravity. Statistical processes are not what militaries are interested in.

It's actually thought that Kessler syndrome is kind of already happening right now, which is why there's a lot of push right now to try to de-orbit the very large pieces of debris, so they can't act to form further debris.

Why can’t every satellite have a small rocket/firework like thing on the back pointing out to the expanse and if the power goes out or it doesn’t receive a signal from the dead man’s switch for long enough then it ignites? Even with a big mass you don’t need to give it much of a shove downwards in a zero friction environment to speed the de-orbit period up.

I’m sure I’m missing something but it just seems like a no brainer to make the deorbit process speed up with something relatively failsafe, as opposed to hopefully/maybe saving a bit of fuel to push it that way eventually

Satellite failures often involve uncontrolled spinning. So you've turned a piece of debris in a known stable path that will eventually deorbit into a piece of debris on an unknown but potentially energetic orbit.

Satellites do have deorbit thrusters, but they're a lot more deliberate. I think Starlink have a whole separate remote controllable system just for deorbit control.

It happens as fast as it happens. Any actual projection would depend on the specific orbits, masses, volumes, materials, and numbers of satellites - Starlink's orbits have a lot of satellites now. There's a very big difference between "everyone trying to avoid it" and "one of the world's largest space programs trying to cause it" in terms of how much we should be worried about it happening for any given orbit in the near term.

The reason it's a scary outcome is because it's an exponential. It can look like an isolated incident or incidents, then the next day be not practically stoppable.

Even if anti-satellite missiles are too expensive to be used to shoot down thousands of targets, the ground stations could be bombed instead. Hacking the control plane and sending de-orbit commands could be even cheaper.

Starlink satellites use inter-satellite lasers and can send those signals arbitrary distances via multiple satellites. Taking out a ground station will just require routing changes and the constellation will continue to perform.

And you can't just wave around "hacking the control plane". Russia's been trying to interfere with Starlink for a while and they haven't had any long term success. And finally, even if the did somehow get access to the control systems at SpaceX, the satellites can't de-orbit quickly. It takes weeks to de-orbit, over which time they could be commanded to reverse course.

The new generation of Starlink satellites have laser connections between them (which is what the article is discussing). They can send data to the other side of the globe to a friendly country for the ground link. (That’s a less efficient use of the inter-satellite bandwidth, of course, but worth doing for war.)

Pretty feasible for anyone who has enough ballistic missiles to target about 5000 targets, or is willing to invest a couple billion into stocking 5000 overpowered fighter-launched missiles. Starlink isn't that high up, and in military terms 5000 targets isn't that much.

The effort of getting a ballistic trajectory that peaks at 500km is a lot smaller than reaching a stable orbit of that height. And just like WWII aircraft you don't need to hit them, just produce enough shrapnel in their vague vicinity.

The biggest hurdle is the universal international condemnation you would receive for such an act

There's no way Russia can afford to make a significant dent in the number of Starlink satellites, even assuming their ASAT missiles aren't mostly filled with water rather than rocket fuel as a result of corruption.

Missiles are expensive compared to tiny, cheap satellites.

Laser beams are also the replacement for ASAT.

Yes effectively immune to missiles. SpaceX launches a new batch of 22 satellites on average every 4-5 days right now and if needed can launch a new batch every 3 days. You'd have to shoot down thousands of satellites to create enough of a service gap, and keep shooting down the new ones. And the problem is only getting harder with time. Unless you're building up an armada of thousands of anti-satellite missiles that you need to maintain at the ready to do this task, you're not really taking the system down.

I should add that anti-satellite missiles are _large_ missiles. The missiles of this size in the US arsenal are SM-3 missiles (or larger). The number even the US has is only in the high hundreds to possibly low thousands. That's completely out of the ability of Russia. It's maybe possible for China but not in their current stockpiles.

A privately-held strategic advantage?

Like all other US defense companies, why not? Do you think US Navy produces their own ships?

The distinction here is that ships are built by nongovernmental private enterprises, whilst Starlink is operated by a nongovernmental private enterprise. With a somewhat volatile executive.

Which isn't unprecedented. But it's also far from the equivalence your comment suggests.

The US military already uses commercial satellite communication systems.

and commercial sensor system like 'Planet'.

and commercial cargo transport.

And lots of other stuff.

Note that, historically, the US Navy had plenty of its own shipyards, and did produce many of its own ships.

https://en.wikipedia.org/wiki/Category:United_States_Navy_sh...

But that's mostly been "optimized away" in more-recent times, in the name of Capitalism and Campaign Donations.

Offloading the risk on private players, reduces the amount of government investment required, and shields them from any criticism, should the project fail.

Also, if it is that strategically important, the government can just buy SpaceX.

They probably wouldn't have to buy them, if there's a war on they probably have enough legal tools to just require SpaceX to sell them whatever capabilities they have.

https://en.wikipedia.org/wiki/Defense_Production_Act_of_1950

It doesn't really matter who owns it as long as it can be bent towards national goals when it matters.

American vehicle manufacturing was a strategic advantage during WWII because they swiftly pivoted to selling tanks to the government instead of cars to civilians.

It's already been bent towards missile defense https://wikipedia.org/wiki/Starlink#Military_capabilities

Plenty of US strategic advantages are privately held or otherwise very dependent on the private sector. It's fine because the company can't really leave the US.

At that level of strategic usefulness ownership stops mattering if shit hits the fan. It'll simply get commandeered.

A strategic advantage depending on the whims of a single provate company.

Sounds great, what could possibly go wrong?

Assuming imminent domain and pursuant seizure.

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.

Why would we expect faster than fibre?

The speed of light in a vacuum is roughly 50% higher than the speed of light in fiber.

I will note that this is the case for conventional fiber-optic cable. The newer hollow-core fiber cables transmit light at nearly c. As far as I know hollow-core has not seen wide-spread use, but it will be interesting if trans-continental connections switch over.

Will adopting the new cables everywhere mean nearly halving latency all across the board? Sans routing latencies.

This would be huge for realtime gaming across continents.

Any stretch of fibre you replace with hollow core fibre will see latency reduced to two thirds of what it was before. (It would be half if the speed of light in it were double what it is in normal fibre, but it's only 50% faster).

You say sans routing latencies, but these are very much significant for intercontinental communication:

I get 6ms ping to AWS eu-central, which is less than 100km by air from me. I get 114ms to AWS us-east-1, which is roughly 6500km. Now 6500km / (2/3 * c) = ~32ms. So if there were a fibre running in a straight line, time in the fibre would be 32ms. Of course it isn't running in a straight line, so let's say 50ms are pure "light traveling through fibre". Switching all of that to hollow-core would cut that to 33ms, so that's a savings of 17ms or roughly 15% of my total latency.

This is still a very nice savings, but very far off from cutting latency in half.

(Also, it's a single hop from my company network to DE-CIX, one of the largest internet exchanges in the world, so I feel confident saying my results aren't skewed by a bad uplink.)

The area between a starlink receiver on the ground and a satellite isn’t a vacuum

That's a great point, I was curious so I looked it up. Google offered the following:

"The speed of light in air is about 299,705 kilometers per second, or 2.99705 × 10^8 meters per second. This is almost as fast as light travels in a vacuum, slowing down by only three ten-thousandths of the speed of light."

So seems like the speed of light in atmosphere is still a lot faster than fiber.

The speed of light in air is 99.97% of that in a vacuum, vs about 2/3 of c through fiber.

Is attenuation in a vacuum also better?

yes, glass has a non zero amount of absorption which is why Erbium amplification is required.

Also, as pointed out elsewhere, the number of hops is the biggest contributor to latency.

It's possible for starlink to beat radio, because radio can't always go straight to the target. If I wanted a radio link from NY->Tokyo, what would that path look like?

It would look like the HF radio bouncing off the ionosphere. I have contacted someone in Japan from Oregon. The downside of HF is that the bandwidth is low with 30MHz across the entire band.

There was company recently wanting to do high-frequency trading on HF because of the quickest path.

I'm curious how much the curved route affects the effective speed of communication with skywaves. You also have many situations where communication becomes impossible due to space weather or other atmospheric phenomena.

True, it would be bouncing around between ground and the atmosphere (when it works at all).

Optical fiber has an index of refraction of around 1.6, so signals travel at around 0.6c. For a perfectly straight cross-continental link (5,000km) with no delays from amplification/retransmission, that's about 26 milliseconds. Assuming the satellites are directly overhead, Starlink adds another 500km up and down, making the minimum possible latency around 20 milliseconds. The real number might be slightly higher or lower depending on the location of the satellites.

My guess is the real latency depends mostly on the latency of relay nodes (either satellites or routers on earth), not the medium through which signals travel.

Number of hops definitely matters more usually. For example I'm about 150 miles from Azure East US 2 (richmond, va), and at the speed of light that should be sub 2ms round trip, but actual latency to it is ~30ms. But I'm sure I'm going through dozens of switches/routers to get there. What Starlink buys you is that you get to go straight to a satellite, then a laser in a vacuum to other satellite(s) and then a ground station that's likely already at an IXP or very close to one.

Could also be shit routing.

Some big ISPs here refused to locally peer with some cheaper providers, so some packets to a local data centre (5 miles away) in Toronto would round trip through Chicago and back.

If they wanted a direct connection; they wanted them to pay for transit.

That could already be the case. Round trip time to the ~500km orbit is about 4 milliseconds (+ all other network elements before, after and in between). They claim to have a >5000km link running for significant time. Now think of a fibre link of that length and how many repeaters / routers will be needed due to attenuation and physical constraints. I can clearly see a path where Starlink laser links could be a viable option to subsea cables - at least for some priority traffic...

a few random outages which happened near places some oligarch's yacht has visited recently and it'll become the priority backhaul.

I see folks in the Pentagon doing a collective /phew that this project is online in the next decade, multiple times.

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 diagonal, and the packets need to tack back and forth, which wastes distance. Think the streets of Manhattan.

Random thought I just had: What are the odds of a rocket launch crossing through one of these laser links on its way to a higher orbit and disrupting traffic for a fraction of a second?

I know space is really big and so the odds of a rocket hitting a satellite on its way up are incredibly low, but now we're talking about lots of lines between each satellite rather than just the satellites themselves. Are the odds still tiny?

Not that it would be a big deal if it happened, just curiosity.

I think they are still tiny. Also don't networking systems routinely deal with temporary link disruption?

What does that have to do with the odds of rocket induced dropped packets?

Any rocket induced dropped packets will just be resent after the rocket has passed or will be routed over other links.

Lets not forget about clouds, birds, airplanes, hot hair balloons and tons of other things that separate the ground from space.

We have protocols and networks already designed today that deal with this exact problem.

I don’t think there are many birds, aeroplanes, nor hot air balloons in LEO? Are there?! (I doubt clouds too, but meteorological phenomena perhaps?)

I think the GP is saying that we already deal with these problems with downlinks, so accounting for similar problems on crosslinks is a known, and expected quantity.

Yes thank you, forgot to link everything together. We already have point-to-point optical and deal with these issues.

It's absolutely incredibly small, think of how large the surface area of a sphere of LEO and the surface area of these lasers linking the vertices of the 5,289 satellites. The gaps between them are probably hundreds of kilometres. I would imagine that each link has multiple routes so if there was a failure traffic can still be routed in the same way the Internet has many routes.

https://satellitemap.space is pretty amazing but a Starlink satellite looks massive on there, really at the scales we are talking they wouldn't even be a pixel. Do we know how many of the satellites are actually interlinked by lasers?

There’s no friction in space. So the question is not how wide the plume of a rocket engine gets, but how spread out does the vapor trail need to be before it stops being an optical impediment?

Volume is even larger than area…

You’re being condescending. That belongs on Reddit, not here.

If you’re in low earth orbit you’re traveling through rocket exhaust. That doesn’t mean you’re seeing enough to affect optical transmission gain. Or orbital decay. But the notion that you’re going to miss because there’s 100’s of kilometers between fast moving satellites? That’s the part of this conversation that deserves condescension, if anything.

Until one of us does the actually maths and builds a model of the probability of intersection I guess our intuition on this being different is fairly irrelevant, either of us could be wrong. I didn’t really think much about my comment, maybe it was patronising I don’t know. I try not to treat the comments I write here (or receive here either) with much seriousness, often you can take most things I say here as me thinking out loud rather than some planned sarcasm or as you say Reddit type posting.

the odds of a rocket hitting a satellite on its way up are incredibly low

Aside, but it's not left to chance. They only launch when there's a gap in the space traffic.

Fair, but they don't compute and probably can't know the laser paths between Starlink nodes.

Interesting question. It used to be zero, before the satellites and before the rockets, but now is probably not zero.

I think you could take the time a rocket would be in the way and compare it to the time it would take any given satellite link pair to make an orbit to form an estimate of the chance of a single interference. Then multiply by rockets and satellite pairs to form an overall estimate.

I've done some research, I don't have a probability but from what I've found. A Falcon 9 shortly before stage 1 separation is around 50km altitude[0] doing ~2000 m/s. Preseperation the F9 is 70m tall, add 130m for plume[1] so 200m total. At 2000 m/s it'll cover it's own length and plume in 100ms. If the laser link is running at 100 Gbps that's 10Gb of data lost.

Which is actually a lot more then I estimated when I started this math, kinda puts into perspective more then 1 of the scales at play here.

Tl;dr Rockets are fast, data is apparently faster.

[0] Apparently on its longest distance link Starlink intersected 30km altitude

[1] Ref: my ass

It doesn't matter what the odds are; loss of connectivity is going to happen. Packet loss is common across the internet, fortunately we have protocols that can deal with this.

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 quality when they're shooting around Earth with 17.000 miles an hour?

(Meanwhile, me on Earth, has link quality issues due to a speck of dust on a fiber connector)

Phased array antennas probably have a lot to do with this. You can aim the signal more accurately and faster than any mechanical system ever could.

Laser links are not using phased array antennas. It's a physically moving "turret" with a laser and another with a receiver. And they need to be separate units, because the speeds and distances involved are long enough that you are not receiving from the same direction as you are sending.

that you are not receiving from the same direction as you are sending

It's a thrill to think about that. Starlink is really out there.

I bet this is lost on a lot of people. Not to patronize anyone, but what Tuna-Fish is pointing out is that due to the speed of light, the distance between satellites and their relatives velocities, when one satellite is beaming data to another satellite it must aim where the receiving satellite will be, as opposed to where it is now, when the light arrives. Further, the receiver must be looking at where the transmitter was back when the signal was sent, as opposed to where the transmitter is now. And because this is all bidirectional, each satellite must send and receive in different, continuously changing directions at the same time.

I understand what you're saying... But lets check.

Assuming the lenses are about 2 inches across (from photos) and they are 1310nm IR lasers:

https://www.wolframalpha.com/input?i=single+slit+diffraction...

So we have a minimum beam width of 0.0014 degrees.

And the speed of light round trip distance is say 3.3 milliseconds.

So the question is, does the angle between the satellites change faster than 0.0014/0.0033 = 0.42 degrees/second?

Well the worst case is one satellite heading north at 7.4 Km/s and another heading south at 7.4 km/s. Lets assume the satellites are 550 km apart (the distance between planes at the equator), and use the small angle approximation... Comes out as 1.4 degrees per second.

So yes, these satellites do need the ability to aim transmit and receive in different directions! (although they might be able to just defocus the beam a little when angles are changing fast to trade off throughput for design complexity)

Surely the lasers aren't phased arrays.

(Meanwhile, me on Earth, has link quality issues due to a speck of dust on a fiber connector)

It's incredible really. I remember when I was a kid living with my mom on an island, we got broadband relatively late (compared to the rest of the country), as the island required antennas for getting mainland and the island linked, instead of cables. I think it was set up that way because of costs or something, remember it being expensive...

Regardless, the antennas were setup and we finally got broadband, but every time it got a bit windy and/or rainy, the links started to have huge issues, especially if the lake got lots of waves, then the connection simply disappeared.

And now it seems almost like magic to me how the same setup is literally done but way above our heads, in a really hostile environment like space.

In some important ways space is actually the least hostile environment. But yeah, it’s still amazing and has its own challenges.

Given this is Gen3 and Gen4 now being launched, it took some figuring out

Relative to the origin satellite I would assume the others are in a fairly fixed position to it. Remember they try to keep them spaced out and even coverage. That means the things are not moving around wildly relative to each other. But to us they are wizzing by. For example I know I am relatively moving fairly quickly to the earths core and pretty fast around the center of the sun. But from my PoV everything around me looks stationary. Also there is not a lot of dirt up there.

Their exact position in space can be calculated very precisely. The Starlink terminals do this as well.

The rate of change of their relative positions is what matters. At 5400km distance this is likely slowish so that tracking is not a big issue as long as position is well known, which it is.

Re. Link quality: laser, line of sight, most of the trip is in vacuum and the rest in very sparse atmosphere. So interferences are likely quite low.

3M just invented a new fiber interconnect thing to mitigate the dust issue: https://www.3m.com/3M/en_US/data-center-us/applications/inte...

Maybe the future of usb in 10 years :)

The current Starlinks satellites aren't small. They are almost a ton and 13ft by 9ft.

Even the original ones weren't that small weighing 570lb.

I just noticed that they were launching their first satellites in 2019. It's impressive that they are now able to casually talk about the different routing options for the data streams to remote areas just 5 years after that.

At first this sounded like an utopian dream but now it looks like common infrastructure that has a place in everyones life.

This must have been the same feeling when the first landlines were installed. The very first lines were a sensation and then after only a few years it becomes normal quickly.

I think it's likely a bad idea at this point to bet against Elon - he seems to make more good decisions than bad decisions, and is able to attract and keep the talent that is enabling his companies to snowball exponentially towards reaching the abundance of the universe.

My deepest hope currently is that the riches of the universe now on the horizon of being relatively easily accessible, in a systematic and efficient way, will lead to the military industrial complex profit seeking to redirect their efforts to mining the riches of the our solar system and beyond, rather than likely mostly inadvertently driving for hell on Earth.

Past performance is a piss poor indicator of future performance.

You can’t deny (I don’t think) that the things he’s done are amazing. He’s in the zone where he’s smelt too many of his farts though, and believes he can do no wrong, which is historically a very bad place to be. I hope, for all of the awesome things he’s said he’d like to do, that they don’t come agutsa due to that

the things he's done are amazing

The things he's _purchased_ are amazing.

The things he purchased were fine. They became revolutionary under him.

The man has a lot of flaws and since covid drifted into ideologies I don't agree with. I also wouldn't buy a Tesla. But there is no denying that both Tesla and SpaceX revolutionized their respective industries. And it seems safe to say that neither would have managed to do this without Musk. And at least SpaceX manages to sustain a substantial lead over the competition and continues revolutionizing industries.

This is obviously untrue. what you’re really saying is “I don’t agree with Elons views so it would be uncomfortable for me to think that he has some admirable qualities, so I don’t allow myself to think about it”

It's amazing the mental gymnastics otherwise intelligent people reach for just to allow themselves to feel superior over someone whose politics they disagree with.

Past performance is the only data available to help predict the future.

Don't forget about prophecy

Prophecy generally falls in line with "any sufficiently advanced technology is indistinguishable from magic.”

If you have enough real-world data, and learned the patterns of history, along with fundamental principles that seem to be precursors or prerequisites to change, then a prophet is more or less someone with a honed and an extended-expanded open mind neural network compared to most.

P.S. It's why it's a really good idea to allow immigrants fleeing from communist countries, as they'll be best and perhaps first to detect and sound the alarm bells if fascism patterns begin to emerge in their new country.

Past performance is a piss poor indicator of future performance.

This is such a baseless and almost comically wrong heuristic I'm curious how it's one you landed on. I'm earnestly curious, do you use the same heuristic in other areas of your life?

If you were in the market for a car, would you let the past performance of other vehicles you've owned influence that decision? It seems to me to be such a simple and fundamental part of decision making, I'm fascinated you've gotten along thus far without it.

"We actually serve over lasers all of our users on Starlink at a given time in like a two-hour window"

I can't figure out what this sentence means.

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.

Have you posted that data anywhere? I'm currently on a 10mbps DSL connection and considering StarLink, but have so far been scared away by the cost and concerns about latency, so I'm always on the lookout for real world data.

My pings roughly 60-80 no matter if I’m going to a friends server down the road or across the world. Before starlink, my rural internet would be lucky to get below 120. For what that’s worth.

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

That any SpaceX user who has a connection established for >2h will have their data sent not via the classic path "ground - satellite - ground" at least once during the connection, but via "ground - satellite 1 - satellite 2 - ground".

Don’t you mean 42million Gigabytes?

I was going to put 336,000,000,000,000,000 bits/day, but it seamed a bit overkill.

*seemed

I dont think theres anything having to do with seams or fabric in this conversation

Been quite a lot of discussion of both of those things in this thread!

Isn’t that equivalent? What does it help to use GB instead of PB?

https://news.ycombinator.com/item?id=39199368

But how do they beam copies of the space to space links down for wiretapping, as Iridium does?

At the ground stations

Starlink is rolling out "direct to cell" connections, where the satellites connect directly to GSM cell phones. Is any ground station involved in a cell to cell call?

You could imagine a situation where they can do that.

But practically what happens is the phone connects to a sat, the sat connects to a local ground station, then across conventional fiber to another ground station, up to a sat and then down to the other phones.

The are likely doing that because regulation and so on. But the do what you suggest.

GS is layer 2. It's done at the POP's like every other company

Global internet traffic is estimated to be 3 yottabytes per day. So Starlink is now carrying one of out every 77 million parts of worldwide traffic. Wow, that's small.

EDIT: there's some confusion information out there. With a more conservative estimate of 150.7 exabytes per month, Starlink gets 1 part of 119, which is more impressive.

The quoted number is only for inter-satellite laser links, not for other methods of information transmission.

Most of the traffic is probably just bounced off the satellite down to the nearby ground station still.

Where do you get 3 yottabytes? That is difficult to believe. I see 150 exabytes per month [1], about a thousand times less.

https://gitnux.org/internet-traffic-statistics/ [1]

https://www.statista.com/statistics/216335/data-usage-per-mo...

Has anyone tried Starlink? I super curious as to whether it's a decent drop in replacement for the ISP have been using at home, and have had trouble with since day one. I won't mention any names (but I will say that it sounds a bit like Smodabone). What is the latency like? The variability of the up/down? Does it do what it says on the tin? Is (non-professional) online gaming a go?

My experience, a year of use - 300Mbps down pretty consistently, 40Mbps up, 40-60ms latency, fine for gaming for the most part, and the drop outs are unnoticeable short when they do infrequently happen. Never had an outage more than 10 seconds.

They’ve also nearly halved the price since I signed up.

Has anyone tried Starlink? I super curious as to whether it's a decent drop in replacement for the ISP have been using at home

I use it when I'm venturing around my rural area, which has spotty (or zero) LTE and broadband. It's awesome for that, literal game-changer.

But it does suffer from downtime, sometimes poor reception, bit of lag, etc. It's the difference between 99% uptime and 99.999999%; you'll notice if you're using it all day, every day. It's also more expensive than my home broadband for lower speeds. I don't think you could replace your ISP, unless your ISP is pretty bad.

Been using it since it was first available. Latency is fine, speeds are good and steady. Occasional outages of several hours every few months or so, but improving as time goes on.

Only complaint is that their DHCP server is buggy so if you don't use their blessed router, you can expect outages when you get transitioned to a new base station and starlink expects your IP to have changed, but it doesn't, or sometimes when your IP lease expires. Took me months to figure out that was the issue. I run almalinux on my router so I just have a script that checks a heartbeat and if it gets interrupted it will nmcli down the wan interface and back up, which usually gets a new IP. Though sometimes it will give the special IP to my router that is supposed to go to the blessed router.

Overall I do recommend, but have a backup ISP if always up is important.

I hate that PCMag ignores browser preferred language lists. It switches the language on my geo IP address which is a language I cannot read.

This is a serious annoyance for me all day long, across the internet. Have you found most sites respect your preferred languages list?

For Google, I found setting my browser to "Accept-Language: en,sv" when I live in Denmark was sufficient — just English and they seem to assume I can't configure the browser and want the local language.

PCMag serves me English, with "en-GB,en", though I don't know if they would support Danish anyway.

The amount of bleeding edge innovation that is rapidly developed and deployed into production in Musks companies is incredible.

The amount of bleeding edge innovation that is rapidly developed and deployed into production in Musks companies is incredible.

SpaceX for sure.

Hard to argue that Tesla is "bleeding edge" anymore; they maintain some advantages, but have fallen behind in other domains.

What are you talking about - weather you think it will work or not, no other company is collecting training data and attempting to solve FSD in the same order of magnitude as Tesla. (last is saw, TSLA collects more video data in 1.5 years then Waymo does in 1 year)

FSD12 is end-to-end neural nets and the videos are pretty impressive. Who else is doing that ?

Somewhat tangential: I assume that Starlink is not yet profitable. How many customers do they need to become profitable?

I recall reading they were profitable on a quarterly basis at end of 2023.

Is it possible one of these laser satellites miss and hit you in the eye? Would that blind a man?

No. The focus of a laser beam is not constant over these large distances. It is the same effect you get if you use a laser pointer over large distances. The spot becomes large quickly.

Isn’t the user experience with starlink pretty abysmal for the average user? Both the service and the customer service?

It's pretty average ish.

You can try it out for 30 days and form your own opinion.

When will we see data centers in space?

I think the biggest hurdle would be heat dissipation. Solar power is plentiful, but all that energy then has to be radiated away somehow.

Are they using Mynaric technology?

Internet says no: https://www.cnbc.com/2021/11/19/german-space-lasers-company-...

42M GB Per day = 3.9tbps

M GB

I can hear the SI crying.

[dupe] https://news.ycombinator.com/item?id=39199368

OP was posted earliest so I guess we'll merge the other threads hither. Thanks!

3.65 days of downtime isn't going to be winning any prizes.

If near a ground station, can't the satellites just use their standard radio links to cover that?

Might be an issue for Antarctica and major seas.

My novice view....Laser connections are point to point, so they can be between satellites....But to the end user equipment,having those many point to point laser connections might be too difficult or impractical to achieve...So that's where they use radiowaves, which means any satellite over the horizon can talk to a dish...

Is that a lot?

Just for context, here's SDA's Open Standard on how they expect to do connections over Optical Links. I assume the starlink terminals work in a similar manner:

https://www.sda.mil/wp-content/uploads/2023/06/SDA_OCT_Stand...

The article mentions that they were able to stream video from a starlink satellite as it was de-orbiting - it would be neat to see the video of that, even if it cuts off as the laser link losing connection (or the satellite burns up)

Wait, I thought only Kuiper has laser.

4 nines uptime is great, but I would think the SNR matters more in a packet switched network like this. There are conditions that may lead to a very low SNR.

I’m waiting for two things:

1. Full-circumference world round-trip latency sat to sat (yes it has to go to ground to “count” but I just want to know what the number is)

2. Deployed LEO servers running with laser communication to the Starlink satellites. Preferably gaming or CDN since either is a great way to verifiably test the limits.

This post currently has 420 points, I bet Musk would like that (wont vote to keep it this way)

That's around 3.9 Tb/s, in case you are wondering.

If I send one byte and it hops through ten satellites, is SpaceX counting that as ten bytes of data?