10 ms·

Since the linked article is somewhat ambiguous about this, and other commenters appear to be getting confused about the purpose and value of the laser links as

by snoshy 6y ago

Since the linked article is somewhat ambiguous about this, and other commenters appear to be getting confused about the purpose and value of the laser links as well: these laser links are purely intended for satellite-to-satellite communications for Starlink. They are not (at least at this time, and for the foreseeable future) intended for ground-to-satellite communications. The value that sat-to-sat laser links provide is that they create a low latency, high bandwidth path that stays within the Starlink satellite network. Before these 10 satellites, each Starlink satellite has only been capable of communicating directly to ground terminals (either consumer, transit, or SpaceX control). For traffic that is intended to move large geographic distances (think transcontinental), this can require several hops back and forth between ground and space, or the traffic from the user terminal is exited at a node that is geared for transiting traffic and most of the data transits along existing ground Internet links. By performing this type of transit directly in space, and exiting at a transit node nearest the destination for the data, you greatly reduce latency. Bandwidth still might not be great, but what this does is unlocks a very financially lucrative consumer use case: low latency finance traffic and critical communications. There are many use cases around the world where shaving even 10-20 milliseconds of latency on a data path can unlock finance and emergency capabilities, and this is a long fought battle throughout the history of these industries. As an example, if you got a piece of news about a company in Australia, and wanted to trade on it as quickly as possible in USA, if you can beat your competitors by 10-20 milliseconds, that can mean a lot of money. Laser comms for Starlink sats have long been planned, but have historically proven to be quite hard to get working. They also depend on a sufficient critical mass of satellites so that a given sat actually does have another sat within lock to send the traffic towards.

martinald 6y ago
I think the other important use case is that sats without a ground station in view can backhaul traffic to another set of sats (for cruise ships or remote islands).
- walrus01 6y ago
  even just the ability to hop 1 satellite can greatly extend the range of one spacex earth station. right now, as the parent poster mentions, the moving LEO satellites need to be simultaneously in view of the CPE antenna and a spacex earth station. and also relatively overhead of the CPE antenna, since the starlink customer terminal is a phased array that does dual beamforming in a 'cone' of view directly above it. just because a satellite is visible 5, 10 or 15 degrees above the horizon from the POV of the CPE doesn't mean it can talk to it. the system is definitely reliant upon a fairly high satellite density. with the ability of the satellite that's generally overhead of a starlink earth station to talk to the satellites immediately behind, and preceding it in its orbital plane, and then those two additional satellites to talk to the CPEs underneath them, the possible coverage area can be greatly increased. 3D visualization of starlink orbits and coverage footprints: https://satellitemap.space/ https://satellitemap.space/
- briffle 6y ago
  I had a friend that worked at the south pole for a year. They had a few hours a day they could access their main communications satellite. Something like this could be a game change for remote research stations..
iso1631 6y ago
Not just low latency. Without satelite-satelite communication, both grounds stations have to be able to see the same satellite. In GEO that's not a problem - a lot of the planet is in sight. You have a ground station in New York and you can bounce off a satellite over the Atlantic and land the signal in Nigeria just fine. With Starlink the orbits are really low, so the distance to the ground station is low. That's fine if you are in the backwoods in Washington and bounce to a receiving station 100 miles away in Seattle, it's no good if you're at sea, or (in this case) at an Antarctic station -- one which can't even see GEO satelites.
- Gravityloss 6y ago
  The field of view from the satellite is 5000 km, though reception probably gets a lot worse at lower angles for a multitude of reasons. Hope I calculated right. https://www.wolframalpha.com/input/?i=2*6300*arccos%286300%2F6900%29 https://www.wolframalpha.com/input/?i=2*6300*arccos%286300%2...
  - walrus01 6y ago
    the starlink beta test customer terminals only have a cone shaped view of suitable beam forming ability and gain above them, so the 4000 km is a lot less in usable practice. they can't talk to a satellite that's 15-20 degrees above the horizon for instance, it'll only work when the satellite rises higher in its general field of view.
    - namibj 6y ago
      The horizon limitation is primarily regulatory. Given that limitation, it doesn't make sense for them to extend the cone closer to the horizon than their flat phased array can do.
      - shaklee3 6y ago
        Not true. The antenna itself has a very low scan to keep costs down.
Diederich 6y ago
> Bandwidth still might not be great Right, compared to reasonable in-ground ISPs. I think Starlink sat to Starlink sat links will also help bandwidth, specifically in the case where a given downlink connection is heavily utilized, the system can shunt traffic to another slightly less ideal but less utilized ground station. > unlocks a very financially lucrative consumer use case That's a bingo! I think there's a pretty good chance that this could turn into a pretty epic cash cow for Starlink.
- rtkwe 6y ago
  I do wonder how much of a draw Starlink will be versus terrestrial microwave for things like HFT firms. Guess it will do really well for linking further afield exchances like Hong Kong and NYSE where a straight line microwave route isn't practical so the extra distance added by the orbit doesn't matter as much.
  - walrus01 6y ago
    a lot of serious HFT for transcontinental stuff moved to HF radio some years back, with big-ass yagi-uda antennas aimed between locations like the CME datacenter, london, tokyo, new york. it's very low data rate but also guaranteed lower latency than the submarine cables.
    - rtkwe 6y ago
      OK so even that will be hard to break into except as a wider bandwidth option which would have some applications the HFT, but it'd be hard since latency is king there. Maybe with that out of the picture other uses like telepresence for remote surgery can edge in. I've been waiting for a while for that to really take off seems like an awesome way to provide services you couldn't afford to to remote places.
      - Diederich 6y ago
        > latency is king there I have read that Starlink, given sat to sat relays, should be able to beat any possible ground based system as long as the distances are great enough. Does that match your understanding of this?
JumpCrisscross 6y ago
Sat-to-sat laser links are also much more secure than undersea cables.
- ornornor 6y ago
  Can’t anyone (well, anyone with state kind of money) observe the laser and at least dump it with perfect accuracy to keep for later decryption? I’d think tapping n undersea cable is more work than observing light going from sat to sat? I’m just spitballing here, I have no idea what’s possible or not but I’d be curious to know.
  - jandrese 6y ago
    I think it would require someone to fly a spy sat up near one of the SpaceX sats. From the ground the atmosphere would attenuate the signal too badly and you'd only have visibility for a few minutes at a time as it passes overhead maybe. In practical terms I don't think it's a major concern. Much more likely that the spy agencies would tap the lines coming out of the ground stations.
    - JumpCrisscross 6y ago
      > Much more likely that the spy agencies would tap the lines coming out of the ground stations Which is a significant step backwards for e.g. Russia. Currently, all data between Asia and North America runs on cables. Anybody can spy on those. If those data did satellite laser hops, only those with ground stations would have access. Everyone else gets locked out.
      - sfblah 6y ago
        The company I work for changed its internal routing of data to use encryption for 100% of traffic crossing the public internet. I have to think everyone else is doing this as well. Is spying on cables like this even useful? How would ay usable data be extracted?
ChuckMcM 6y ago
Exactly, there was a great animation posted here once that showed the hobs with and without lasers. Given that there are examples of 44+ terabits[1] being transmitted optically I am not too worried about the bandwidth. I'd love to be on the Starlink team, they are building some really cutting edge stuff. There are not many places or times where you can have such a big impact on the world and their team happens to be one of them. Good times. [1] https://www.sciencedaily.com/releases/2020/05/200522095504.htm https://www.sciencedaily.com/releases/2020/05/200522095504.h...
- snoshy 6y ago
  This seems overly ambitious, and not likely to translate to laser satellite comms links. Remember these sats are in low LEO, so there is at least some amount of non-uniform atmospheric medium to create optical distortion that you wouldn't have in a tightly controlled environment from your link (chip, datacenter, what have you). Then there's the issue of signal attenuation at distances like these, along with the power budget from the solar panels to ensure that you aren't burning all your power just on laser comms. I can't imagine these links would be anything more than 1:1 at any given time, at least not at first. Maybe later they might be able to handle simultaneous laser links from 1:3 or something like it, but I highly doubt that's their current capability. Even some of the best latest ground-to-sat laser comms links are on the order of ~7 gigabits per second. [1] I imagine those are far larger sats than Starlink, and their entire power and thermal budget is likely spent on comms. And the ground stations can be orders of magnitude larger and power hungry in relation to a Starlink sat. Note also that this is from GEO, so you aren't likely having to handle substantial relative movement either. [1] https://en.wikipedia.org/wiki/Laser_communication_in_space#2011-present https://en.wikipedia.org/wiki/Laser_communication_in_space#2...
  - BenjiWiebe 6y ago
    Seems like a LEO-to-LEO laser link would be shorter, lower noise, and lower power for the same bandwidth as a GEO-Earth link.
  - lutorm 6y ago
    Space to ground is a lot harder than space to space. There is no atmosphere to deal with and in most cases the relative velocity is lower.
employedbydlr 6y ago
German aerospace agency DLR sent a laser terminal for satellite to ground communication on the same ride-share -> https://www.dlr.de/kn/desktopdefault.aspx/tabid-17435/ https://www.dlr.de/kn/desktopdefault.aspx/tabid-17435/
- namibj 6y ago
  Thanks for mentioning. I dug up the paper with the technical details. I did not find anything suggesting it'd be used productively for the satellite if it manages to deliver. Do you have anything about that you can tell/link? I'd be curious what the initial design weight was, before the thermal expansion problem that caused the aluminium block. As for the data rate, it seems a mechanically simplistic fold-out mirror (released during deploy, say with a current pulse into a shape-memory-alloy torsion spring to delay the unfolding until after the ejection, or just a simple friction break and a normal torsion spring) could significantly decrease the beam width when made from e.g. zerodur and fabricated as an offset parabolic dish. Slightly modifying the refractive collimating optics of the current design should make that approach possible. I'd expect vibration in space to be a negligible issue, so an edge-mounted mirror should be stiff enough. https://elib.dlr.de/135960/ https://elib.dlr.de/135960/ https://elib.dlr.de/135960/1/1150604.pdf https://elib.dlr.de/135960/1/1150604.pdf
nickik 6y ago
The real value is not super low latency communication, but rather airplanes and ships out of reach of normal base stations. I have seen no evidence that traders will be the primary users. Do you have any evidence or cases where they are doing or planning this. Are you just guessing?
- temp667 6y ago
  In my space especially with video conferencing people are willing to spend a premium for lower latency for audio / video conferencing links. So there may be a market there (if you can backhaul phone, video, audio conference traffic) where even 10 - 20 ms in savings may be noticable. Another may be gaming. Another is as you say planes and ships out of reach of ground stations (very sparse situation however).
- ncmncm 6y ago
  Every single high-speed trader's ears perked up instantly when news of this came out. They already spend huge amounts on microwave links overland between e.g. Chicago and New York, for just a few milliseconds advantage over fiber. Starlink gives them the same opportunity across Atlantic, Pacific, and Indian oceans. You can bet that there will be orbits that exactly link London and New York, New York and Tokyo, New York and Singapore, London and Singapore, etc. Traffic not sent under extra-high tariffs will be artificially delayed enough milliseconds to match fiber. It would not be surprising if these low-latency contracts, for traffic amounting to well under 0.1% of total capacity, provide 10% of revenue. It would also not be surprising if future satellites have tens of TB of storage onboard to proxy streaming for the highest-demand shows of the moment, and broadcast capability to multiple ground stations simultaneously for live streams, particularly soccer matches. Most likely, aside from financial transaction data, routing will always offload packets to ground terminals as early as possible. I strongly doubt zigzag routing will happen at all.
xibalba 6y ago
So are these laser equipped says inserted between/within the "chain" of previously deployed starlink says?
- NortySpock 6y ago
  Either they will retire old chains of satellites or just start new chains.
  - ceejayoz 6y ago
    The older satellites self-retire after a couple years, anyways, just by running out of fuel and deorbiting.
- snoshy 6y ago
  Not quite. In order for a laser sat to talk to another sat, the second sat needs to also have laser comms hardware on it. Given that these were the first 10 to boast of such hardware, initially they'll only be talking to each other. Over time, as Starlink pitches more sats into orbit with laser comms, they will have more and more peers to talk to. As the sister comment implies though, Starlink sats are in low Low-Earth-Orbit (LEO) so they experience non-zero drag from the atmosphere. This slows them down, causing them to gradually fall back to Earth, creating a natural expected service lifetime for each satellite in orbit. So the expectation is that SpaceX will have to continually put up more and more replacements indefinitely as older sats decay and burn up in the atmosphere. These 10 laser sats are just the latest among a string of sats that are yet to come online with newer and better capabilities.
- Tuna-Fish 6y ago
  This particular set goes into their own plane in a much more highly inclined orbit than any of the existing ones.
benlivengood 6y ago
There are lots of fascinating problems to solve. The telemetry and tracking itself for the laser links. All the satellites need fairly accurate orbital information from all other satellites; there will be several thousand satellites capable of performing autonomous orbital adjustments to avoid debris and for their own station keeping. There has to be a convenient and reliable fallback for automatically syncing satellites with the rest of the network after a reboot or loss of communication. The packet network needs to maintain an efficient routing table and provide low packet loss to end-users. My guess is that the only practical choice will be establishing a large number of point-to-point channels with their own retry/error-correction management. TCP/IP isn't capable of dealing with more than about 1% packet loss and I doubt raw optical/wireless links will be reliable enough especially with topology changes, requiring extensive store-and-forward hardware to buffer transmissions waiting for a reliable route or de-duplicating multicast packets at the receiving end. Reassembly and de-duplication on receipt is theoretically feasible; if a tight reception window can be maintained then specialized hardware could filter duplicates sent over 2 or 3 redundant routes to a local receiver without increasing observed latency or using unreasonable amounts of RAM. A combination approach could allow a tradeoff between using double or triple the raw bandwidth but providing low-latency reliability vs. higher latency with retries while maximizing throughput depending on the current network load. It could also be hardcoded for different traffic classes. I'm not involved in this problem space in any technical capacity but it sounds like a very fun set of problems to solve.
- snoshy 6y ago
  SpaceX continues to genuinely feel like a practical intellectual's playground. They really do have so many fascinating problems to work on. Accurate orbital information might not be necessary or possible, if you can perform broad scanning that can quickly lock in your given target, but it certainly doesn't hurt. The issue is that even having an orbital track, because of the sats being so low in LEO, atmospheric drag will change your orbit rapidly enough that this information can get out of date quite fast. Convenient and reliable fallbacks I feel are largely a solved problem for SpaceX. They've built their Starlink bus by reusing a lot of the software from the Falcon 9, Dragon, and Starship programs that already had to handle even greater levels of reliability. Routing and retransmits are indeed quite a novel area for this kind of service. But the laser link will only be locked on one other peer satellite at any given time, and I don't think they plan on reorienting the sats in order to establish laser comms because of the effect it would have on drag as well as albedo. The former impacts service life per sat, and the latter has been a big rallying cry for Starlink opposition due to the impact it has on astronomy and the visible sky. So if you likely can't reorient to retransmit, your only options are the peer laser link or the ground transit exit node, either or both of which might not exist, but I feel like you would just ack the packets on each hop to your peer and leave it at that.
SheinhardtWigCo 6y ago
> shaving even 10-20 milliseconds of latency on a data path can unlock finance and emergency capabilities The financial upside is clear, but what kind of emergency capabilities do you mean?
- cozzyd 6y ago
  Maybe something like remote-controlled rescue?
- aaron695 6y ago
  I suspect it's just the scam people use for no use i.e. https://xkcd.com/2128/ https://xkcd.com/2128/ But I too was interested to see if they had an actual idea in mind? I would think the computer game market. Maybe other markets that have high end mature users where client side is very good so lower latency might be something that matters relative.
new_realist 6y ago
I question how low latency these links will be, given the sheer number of hops (and thus queues and transceiver modulations) required to span the globe. And, of course, every round trip requires four trips through the atmosphere. Then you have the Manhattan distance of the hops. Maybe dedicated QoS flows along orbital planes stand a chance, not so general Internet traffic. (downvotes don’t change facts, kiddos)
etaioinshrdlu 6y ago
Also, each starlink satellite can use beamforming to very rapidly send narrow beams down to Earth and switch quickly, hundreds of times faster than steering an antenna mechanically. They can't (as far as I know) use beamforming with lasers, so they can't be steered to different terminals as quickly.

by snoshy 6y ago

martinald 6y ago

I think the other important use case is that sats without a ground station in view can backhaul traffic to another set of sats (for cruise ships or remote islands).

walrus01 6y ago
even just the ability to hop 1 satellite can greatly extend the range of one spacex earth station. right now, as the parent poster mentions, the moving LEO satellites need to be simultaneously in view of the CPE antenna and a spacex earth station. and also relatively overhead of the CPE antenna, since the starlink customer terminal is a phased array that does dual beamforming in a 'cone' of view directly above it. just because a satellite is visible 5, 10 or 15 degrees above the horizon from the POV of the CPE doesn't mean it can talk to it. the system is definitely reliant upon a fairly high satellite density. with the ability of the satellite that's generally overhead of a starlink earth station to talk to the satellites immediately behind, and preceding it in its orbital plane, and then those two additional satellites to talk to the CPEs underneath them, the possible coverage area can be greatly increased. 3D visualization of starlink orbits and coverage footprints: https://satellitemap.space/ https://satellitemap.space/
briffle 6y ago
I had a friend that worked at the south pole for a year. They had a few hours a day they could access their main communications satellite. Something like this could be a game change for remote research stations..

iso1631 6y ago

Not just low latency. Without satelite-satelite communication, both grounds stations have to be able to see the same satellite. In GEO that's not a problem - a lot of the planet is in sight. You have a ground station in New York and you can bounce off a satellite over the Atlantic and land the signal in Nigeria just fine. With Starlink the orbits are really low, so the distance to the ground station is low. That's fine if you are in the backwoods in Washington and bounce to a receiving station 100 miles away in Seattle, it's no good if you're at sea, or (in this case) at an Antarctic station -- one which can't even see GEO satelites.

Gravityloss 6y ago
The field of view from the satellite is 5000 km, though reception probably gets a lot worse at lower angles for a multitude of reasons. Hope I calculated right. https://www.wolframalpha.com/input/?i=2*6300*arccos%286300%2F6900%29 https://www.wolframalpha.com/input/?i=2*6300*arccos%286300%2...
- walrus01 6y ago
  the starlink beta test customer terminals only have a cone shaped view of suitable beam forming ability and gain above them, so the 4000 km is a lot less in usable practice. they can't talk to a satellite that's 15-20 degrees above the horizon for instance, it'll only work when the satellite rises higher in its general field of view.
  - namibj 6y ago
    The horizon limitation is primarily regulatory. Given that limitation, it doesn't make sense for them to extend the cone closer to the horizon than their flat phased array can do.
    - shaklee3 6y ago
      Not true. The antenna itself has a very low scan to keep costs down.

Diederich 6y ago

> Bandwidth still might not be great Right, compared to reasonable in-ground ISPs. I think Starlink sat to Starlink sat links will also help bandwidth, specifically in the case where a given downlink connection is heavily utilized, the system can shunt traffic to another slightly less ideal but less utilized ground station. > unlocks a very financially lucrative consumer use case That's a bingo! I think there's a pretty good chance that this could turn into a pretty epic cash cow for Starlink.

rtkwe 6y ago
I do wonder how much of a draw Starlink will be versus terrestrial microwave for things like HFT firms. Guess it will do really well for linking further afield exchances like Hong Kong and NYSE where a straight line microwave route isn't practical so the extra distance added by the orbit doesn't matter as much.
- walrus01 6y ago
  a lot of serious HFT for transcontinental stuff moved to HF radio some years back, with big-ass yagi-uda antennas aimed between locations like the CME datacenter, london, tokyo, new york. it's very low data rate but also guaranteed lower latency than the submarine cables.
  - rtkwe 6y ago
    OK so even that will be hard to break into except as a wider bandwidth option which would have some applications the HFT, but it'd be hard since latency is king there. Maybe with that out of the picture other uses like telepresence for remote surgery can edge in. I've been waiting for a while for that to really take off seems like an awesome way to provide services you couldn't afford to to remote places.
    - Diederich 6y ago
      > latency is king there I have read that Starlink, given sat to sat relays, should be able to beat any possible ground based system as long as the distances are great enough. Does that match your understanding of this?

JumpCrisscross 6y ago

Sat-to-sat laser links are also much more secure than undersea cables.

ornornor 6y ago
Can’t anyone (well, anyone with state kind of money) observe the laser and at least dump it with perfect accuracy to keep for later decryption? I’d think tapping n undersea cable is more work than observing light going from sat to sat? I’m just spitballing here, I have no idea what’s possible or not but I’d be curious to know.
- jandrese 6y ago
  I think it would require someone to fly a spy sat up near one of the SpaceX sats. From the ground the atmosphere would attenuate the signal too badly and you'd only have visibility for a few minutes at a time as it passes overhead maybe. In practical terms I don't think it's a major concern. Much more likely that the spy agencies would tap the lines coming out of the ground stations.
  - JumpCrisscross 6y ago
    > Much more likely that the spy agencies would tap the lines coming out of the ground stations Which is a significant step backwards for e.g. Russia. Currently, all data between Asia and North America runs on cables. Anybody can spy on those. If those data did satellite laser hops, only those with ground stations would have access. Everyone else gets locked out.
    - sfblah 6y ago
      The company I work for changed its internal routing of data to use encryption for 100% of traffic crossing the public internet. I have to think everyone else is doing this as well. Is spying on cables like this even useful? How would ay usable data be extracted?

ChuckMcM 6y ago

Exactly, there was a great animation posted here once that showed the hobs with and without lasers. Given that there are examples of 44+ terabits[1] being transmitted optically I am not too worried about the bandwidth. I'd love to be on the Starlink team, they are building some really cutting edge stuff. There are not many places or times where you can have such a big impact on the world and their team happens to be one of them. Good times. [1] https://www.sciencedaily.com/releases/2020/05/200522095504.htm https://www.sciencedaily.com/releases/2020/05/200522095504.h...

snoshy 6y ago
This seems overly ambitious, and not likely to translate to laser satellite comms links. Remember these sats are in low LEO, so there is at least some amount of non-uniform atmospheric medium to create optical distortion that you wouldn't have in a tightly controlled environment from your link (chip, datacenter, what have you). Then there's the issue of signal attenuation at distances like these, along with the power budget from the solar panels to ensure that you aren't burning all your power just on laser comms. I can't imagine these links would be anything more than 1:1 at any given time, at least not at first. Maybe later they might be able to handle simultaneous laser links from 1:3 or something like it, but I highly doubt that's their current capability. Even some of the best latest ground-to-sat laser comms links are on the order of ~7 gigabits per second. [1] I imagine those are far larger sats than Starlink, and their entire power and thermal budget is likely spent on comms. And the ground stations can be orders of magnitude larger and power hungry in relation to a Starlink sat. Note also that this is from GEO, so you aren't likely having to handle substantial relative movement either. [1] https://en.wikipedia.org/wiki/Laser_communication_in_space#2011-present https://en.wikipedia.org/wiki/Laser_communication_in_space#2...
- BenjiWiebe 6y ago
  Seems like a LEO-to-LEO laser link would be shorter, lower noise, and lower power for the same bandwidth as a GEO-Earth link.
- lutorm 6y ago
  Space to ground is a lot harder than space to space. There is no atmosphere to deal with and in most cases the relative velocity is lower.

employedbydlr 6y ago

German aerospace agency DLR sent a laser terminal for satellite to ground communication on the same ride-share -> https://www.dlr.de/kn/desktopdefault.aspx/tabid-17435/ https://www.dlr.de/kn/desktopdefault.aspx/tabid-17435/

namibj 6y ago
Thanks for mentioning. I dug up the paper with the technical details. I did not find anything suggesting it'd be used productively for the satellite if it manages to deliver. Do you have anything about that you can tell/link? I'd be curious what the initial design weight was, before the thermal expansion problem that caused the aluminium block. As for the data rate, it seems a mechanically simplistic fold-out mirror (released during deploy, say with a current pulse into a shape-memory-alloy torsion spring to delay the unfolding until after the ejection, or just a simple friction break and a normal torsion spring) could significantly decrease the beam width when made from e.g. zerodur and fabricated as an offset parabolic dish. Slightly modifying the refractive collimating optics of the current design should make that approach possible. I'd expect vibration in space to be a negligible issue, so an edge-mounted mirror should be stiff enough. https://elib.dlr.de/135960/ https://elib.dlr.de/135960/ https://elib.dlr.de/135960/1/1150604.pdf https://elib.dlr.de/135960/1/1150604.pdf

nickik 6y ago

The real value is not super low latency communication, but rather airplanes and ships out of reach of normal base stations. I have seen no evidence that traders will be the primary users. Do you have any evidence or cases where they are doing or planning this. Are you just guessing?

temp667 6y ago
In my space especially with video conferencing people are willing to spend a premium for lower latency for audio / video conferencing links. So there may be a market there (if you can backhaul phone, video, audio conference traffic) where even 10 - 20 ms in savings may be noticable. Another may be gaming. Another is as you say planes and ships out of reach of ground stations (very sparse situation however).
ncmncm 6y ago
Every single high-speed trader's ears perked up instantly when news of this came out. They already spend huge amounts on microwave links overland between e.g. Chicago and New York, for just a few milliseconds advantage over fiber. Starlink gives them the same opportunity across Atlantic, Pacific, and Indian oceans. You can bet that there will be orbits that exactly link London and New York, New York and Tokyo, New York and Singapore, London and Singapore, etc. Traffic not sent under extra-high tariffs will be artificially delayed enough milliseconds to match fiber. It would not be surprising if these low-latency contracts, for traffic amounting to well under 0.1% of total capacity, provide 10% of revenue. It would also not be surprising if future satellites have tens of TB of storage onboard to proxy streaming for the highest-demand shows of the moment, and broadcast capability to multiple ground stations simultaneously for live streams, particularly soccer matches. Most likely, aside from financial transaction data, routing will always offload packets to ground terminals as early as possible. I strongly doubt zigzag routing will happen at all.

xibalba 6y ago

So are these laser equipped says inserted between/within the "chain" of previously deployed starlink says?

NortySpock 6y ago
Either they will retire old chains of satellites or just start new chains.
- ceejayoz 6y ago
  The older satellites self-retire after a couple years, anyways, just by running out of fuel and deorbiting.
snoshy 6y ago
Not quite. In order for a laser sat to talk to another sat, the second sat needs to also have laser comms hardware on it. Given that these were the first 10 to boast of such hardware, initially they'll only be talking to each other. Over time, as Starlink pitches more sats into orbit with laser comms, they will have more and more peers to talk to. As the sister comment implies though, Starlink sats are in low Low-Earth-Orbit (LEO) so they experience non-zero drag from the atmosphere. This slows them down, causing them to gradually fall back to Earth, creating a natural expected service lifetime for each satellite in orbit. So the expectation is that SpaceX will have to continually put up more and more replacements indefinitely as older sats decay and burn up in the atmosphere. These 10 laser sats are just the latest among a string of sats that are yet to come online with newer and better capabilities.
Tuna-Fish 6y ago
This particular set goes into their own plane in a much more highly inclined orbit than any of the existing ones.

benlivengood 6y ago

There are lots of fascinating problems to solve. The telemetry and tracking itself for the laser links. All the satellites need fairly accurate orbital information from all other satellites; there will be several thousand satellites capable of performing autonomous orbital adjustments to avoid debris and for their own station keeping. There has to be a convenient and reliable fallback for automatically syncing satellites with the rest of the network after a reboot or loss of communication. The packet network needs to maintain an efficient routing table and provide low packet loss to end-users. My guess is that the only practical choice will be establishing a large number of point-to-point channels with their own retry/error-correction management. TCP/IP isn't capable of dealing with more than about 1% packet loss and I doubt raw optical/wireless links will be reliable enough especially with topology changes, requiring extensive store-and-forward hardware to buffer transmissions waiting for a reliable route or de-duplicating multicast packets at the receiving end. Reassembly and de-duplication on receipt is theoretically feasible; if a tight reception window can be maintained then specialized hardware could filter duplicates sent over 2 or 3 redundant routes to a local receiver without increasing observed latency or using unreasonable amounts of RAM. A combination approach could allow a tradeoff between using double or triple the raw bandwidth but providing low-latency reliability vs. higher latency with retries while maximizing throughput depending on the current network load. It could also be hardcoded for different traffic classes. I'm not involved in this problem space in any technical capacity but it sounds like a very fun set of problems to solve.

snoshy 6y ago
SpaceX continues to genuinely feel like a practical intellectual's playground. They really do have so many fascinating problems to work on. Accurate orbital information might not be necessary or possible, if you can perform broad scanning that can quickly lock in your given target, but it certainly doesn't hurt. The issue is that even having an orbital track, because of the sats being so low in LEO, atmospheric drag will change your orbit rapidly enough that this information can get out of date quite fast. Convenient and reliable fallbacks I feel are largely a solved problem for SpaceX. They've built their Starlink bus by reusing a lot of the software from the Falcon 9, Dragon, and Starship programs that already had to handle even greater levels of reliability. Routing and retransmits are indeed quite a novel area for this kind of service. But the laser link will only be locked on one other peer satellite at any given time, and I don't think they plan on reorienting the sats in order to establish laser comms because of the effect it would have on drag as well as albedo. The former impacts service life per sat, and the latter has been a big rallying cry for Starlink opposition due to the impact it has on astronomy and the visible sky. So if you likely can't reorient to retransmit, your only options are the peer laser link or the ground transit exit node, either or both of which might not exist, but I feel like you would just ack the packets on each hop to your peer and leave it at that.

SheinhardtWigCo 6y ago

> shaving even 10-20 milliseconds of latency on a data path can unlock finance and emergency capabilities The financial upside is clear, but what kind of emergency capabilities do you mean?

cozzyd 6y ago
Maybe something like remote-controlled rescue?
aaron695 6y ago
I suspect it's just the scam people use for no use i.e. https://xkcd.com/2128/ https://xkcd.com/2128/ But I too was interested to see if they had an actual idea in mind? I would think the computer game market. Maybe other markets that have high end mature users where client side is very good so lower latency might be something that matters relative.

new_realist 6y ago

I question how low latency these links will be, given the sheer number of hops (and thus queues and transceiver modulations) required to span the globe. And, of course, every round trip requires four trips through the atmosphere. Then you have the Manhattan distance of the hops. Maybe dedicated QoS flows along orbital planes stand a chance, not so general Internet traffic. (downvotes don’t change facts, kiddos)

etaioinshrdlu 6y ago

Also, each starlink satellite can use beamforming to very rapidly send narrow beams down to Earth and switch quickly, hundreds of times faster than steering an antenna mechanically. They can't (as far as I know) use beamforming with lasers, so they can't be steered to different terminals as quickly.