3 ms·

The bandwidth is not expensive. There is simply a lack of it. Most LEO satellites have 10-20 minutes a day communications window assuming single ground station

The bandwidth is not expensive. There is simply a lack of it. Most LEO satellites have 10-20 minutes a day communications window assuming single ground station. Amount of data you can download from a single pass is a tens or hundreds megabytes per day. One high-resolution camera image can be easily over 10MB.

lozaning 6y ago
Very interesting, thanks for the follow up. Would this issue be any way relieved with things like AWS ground station? If you can only see a ground station from a satellite for 20 minutes, could you just add more ground stations? Or is that 20 minutes window constrained by something other than having a ground station within receiving range?
- d_silin 6y ago
  More ground stations will definitely make things better, but 24/7 connectivity to assets in LEO will take monumental, Starlink-scale level of effort.
  - chinathrow 6y ago
    Would it be possible to use Starlink for comms if a sat is flying in a lower position?
    - d_silin 6y ago
      In theory, yes. In practice, this will depend more on my negotiation skills when talking to Elon Musk and less on any technical challenge :)
      - portyllo 6y ago
        No, it will not be possible, no matter what Elon says. Starlink operates in portions of the Ku and Ka bands that are reserved for Earth-to-space comms, not for space-to-space comms.
        d_silin 6y ago
        My impression was that Starlink relies on inter-satellite links to route traffic. We can use the same links for our own extended network.
        portillo 6y ago
        The current satellites do not have crosslinks, and in any case, in their FCC filings SpaceX talks about optical crosslinks, not RF.
  - portillo 6y ago
    You can get 24/7 connectivity to LEO right now (and 25 years ago too) using TDRSS. The system costs a fraction of what Starlink will cost, as you only need 3 GEO satellites.
portyllo 6y ago
There is plenty of bandwidth to achieve more than 1 Gbps of throughput from a 3-U cubesat (see Planet with their latest X-band comms-system [1], which results in more than 50 GB per pass). If you really need more than that, new free space optical communications systems under-development will bring multi-Gbps to small-sats [2]. For me, the real problem with nanosats is that they generate barely no power and they are really volume-constrained compared to the bigger birds (so you cannot have high-resolution sensors, and cannot fit in there a good optical-comms system, you need to be mindful of your power consumption all time during the mission...). Finally, note that nowadays Planet downloads 10 TB/day, and they could go up to 40 TB/day once they upgrade their fleet with the latest X-band antenna, which is comparable to the 80 TB/day that DigitalGlobe generates. [1] https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4405&context=smallsat https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4... [2] https://www.tesat.de/images/tesat/products/TOSIRIS_Data-Sheet.pdf https://www.tesat.de/images/tesat/products/TOSIRIS_Data-Shee...

lozaning 6y ago

Very interesting, thanks for the follow up. Would this issue be any way relieved with things like AWS ground station? If you can only see a ground station from a satellite for 20 minutes, could you just add more ground stations? Or is that 20 minutes window constrained by something other than having a ground station within receiving range?

d_silin 6y ago
More ground stations will definitely make things better, but 24/7 connectivity to assets in LEO will take monumental, Starlink-scale level of effort.
- chinathrow 6y ago
  Would it be possible to use Starlink for comms if a sat is flying in a lower position?
  - d_silin 6y ago
    In theory, yes. In practice, this will depend more on my negotiation skills when talking to Elon Musk and less on any technical challenge :)
    - portyllo 6y ago
      No, it will not be possible, no matter what Elon says. Starlink operates in portions of the Ku and Ka bands that are reserved for Earth-to-space comms, not for space-to-space comms.
      - d_silin 6y ago
        My impression was that Starlink relies on inter-satellite links to route traffic. We can use the same links for our own extended network.
        portillo 6y ago
        The current satellites do not have crosslinks, and in any case, in their FCC filings SpaceX talks about optical crosslinks, not RF.
- portillo 6y ago
  You can get 24/7 connectivity to LEO right now (and 25 years ago too) using TDRSS. The system costs a fraction of what Starlink will cost, as you only need 3 GEO satellites.

portyllo 6y ago

There is plenty of bandwidth to achieve more than 1 Gbps of throughput from a 3-U cubesat (see Planet with their latest X-band comms-system [1], which results in more than 50 GB per pass). If you really need more than that, new free space optical communications systems under-development will bring multi-Gbps to small-sats [2]. For me, the real problem with nanosats is that they generate barely no power and they are really volume-constrained compared to the bigger birds (so you cannot have high-resolution sensors, and cannot fit in there a good optical-comms system, you need to be mindful of your power consumption all time during the mission...). Finally, note that nowadays Planet downloads 10 TB/day, and they could go up to 40 TB/day once they upgrade their fleet with the latest X-band antenna, which is comparable to the 80 TB/day that DigitalGlobe generates. [1] https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4405&context=smallsat https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4... [2] https://www.tesat.de/images/tesat/products/TOSIRIS_Data-Sheet.pdf https://www.tesat.de/images/tesat/products/TOSIRIS_Data-Shee...