3 ms·

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

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.
      - walrus01 6y ago
        Indeed, a flat phased array can only have a certain limited gain at elevations and azimuths far away from the direction it's pointed in. One of the reasons if you ever see a flat phased array radar inside the nose radome of a air superiority type fighter jet, they're not fixed but also can be mounted on a sort of pan/tilt platform for steering.
      - namibj 6y ago
        Yes, because e.g. a multi-panel design would be limited by regulations. Hence they decided on the single panel for ROI/cost-efficiency purposes.
walrus01 6y ago
big chunks of antarctica where most of the research base population is located can see geostationary, just at a very low look angle. the whole peninsula, mcmurdo and places at similar latitudes to mcmurdo. it's the pole that has problems seeing geostationary, and has up until very recently been totally dependent on 7-8 hours of coverage a day using big tracking antennas to talk to old geostationary satellites that have wandered somewhat out of their original orbits, so that from the POV of the earth station at pole, they can be communicated with part of the time.
- snoshy 6y ago
  Yea I'm guessing a bunch of researchers at both poles must be rejoicing at the potential for new connectivity this creates with the polar launch.
  - walrus01 6y ago
    The US DoD and Soviets, Russians somewhat solved this problem by putting molniya/tundra orbit communications satellites into orbit for narrowband data and voice, text comms. Has been a thing for 35+ years. But there has been nowhere near enough money available to do something like set up a pair of molniya orbit satellites with long apogee dwell times over the center of antarctica.
    - snoshy 6y ago
      Sure, but that pittance of bandwidth is a far cry from having persistent 24/7 access to a high bandwidth, low latency service like Starlink. Long boring months spent in the darkness with very few recreational outlets now all of a sudden become a lot more attractive with access to the open Internet and your loved ones with no restrictions.
      - walrus01 6y ago
        I can only imagine. For the Amundsen-Scott station people I imagine it will be revolutionary. Assuming that the topology will be additional highly-inclined/polar orbit starlink satellites, communicating with each other in a laser chain, this will be dependent on starlink setting up earth stations near fiber somewhere in southern Chile, Argentina or in South Africa. Or south australia, tasmania, new zealand.

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.
    - walrus01 6y ago
      Indeed, a flat phased array can only have a certain limited gain at elevations and azimuths far away from the direction it's pointed in. One of the reasons if you ever see a flat phased array radar inside the nose radome of a air superiority type fighter jet, they're not fixed but also can be mounted on a sort of pan/tilt platform for steering.
    - namibj 6y ago
      Yes, because e.g. a multi-panel design would be limited by regulations. Hence they decided on the single panel for ROI/cost-efficiency purposes.

walrus01 6y ago

big chunks of antarctica where most of the research base population is located can see geostationary, just at a very low look angle. the whole peninsula, mcmurdo and places at similar latitudes to mcmurdo. it's the pole that has problems seeing geostationary, and has up until very recently been totally dependent on 7-8 hours of coverage a day using big tracking antennas to talk to old geostationary satellites that have wandered somewhat out of their original orbits, so that from the POV of the earth station at pole, they can be communicated with part of the time.

snoshy 6y ago
Yea I'm guessing a bunch of researchers at both poles must be rejoicing at the potential for new connectivity this creates with the polar launch.
- walrus01 6y ago
  The US DoD and Soviets, Russians somewhat solved this problem by putting molniya/tundra orbit communications satellites into orbit for narrowband data and voice, text comms. Has been a thing for 35+ years. But there has been nowhere near enough money available to do something like set up a pair of molniya orbit satellites with long apogee dwell times over the center of antarctica.
  - snoshy 6y ago
    Sure, but that pittance of bandwidth is a far cry from having persistent 24/7 access to a high bandwidth, low latency service like Starlink. Long boring months spent in the darkness with very few recreational outlets now all of a sudden become a lot more attractive with access to the open Internet and your loved ones with no restrictions.
    - walrus01 6y ago
      I can only imagine. For the Amundsen-Scott station people I imagine it will be revolutionary. Assuming that the topology will be additional highly-inclined/polar orbit starlink satellites, communicating with each other in a laser chain, this will be dependent on starlink setting up earth stations near fiber somewhere in southern Chile, Argentina or in South Africa. Or south australia, tasmania, new zealand.