4 ms·

This is the point I'd really like to see some more detail on or discussion on from relevant experts. I'm sure you can build some kind of GNSS with the capabilit

This is the point I'd really like to see some more detail on or discussion on from relevant experts. I'm sure you can build some kind of GNSS with the capabilities of OneWeb satellites, can you build something with similar capabilities to existing GNSS (GPS was original designed in the 70s so was designed with receivers with limited computational capability, with modern capabilities can you build a system that requires lots more satellites for a good fix, where those satellites don't need the same capabilities as a GPS satellite for instance)? If not do you need small tweaks to OneWeb's current platform or a total overhaul to build a GNSS? I can well believe the UK government has been sold on a thing that can't work, but equally I can see reasons it may be possible to use OneWorld's existing platform for a GNSS service.

dr_orpheus 6y ago
One of the biggest drivers of cost on GNSS satellites is the need for an extremely accurate clock. Position is calculated based on a series of ranges to the satellites with a "known" position. That range is calculated is based on a time-of-flight so you need a very accurate time source. The whole Galileo project cost is 10 billion [0] and this is "cheap" compared to the US GPS system. I can't find great numbers for it, but for the cost of building two new GPS satellites this year is $1.8 billion [1] and operating cost for the existing constellation I believe is on the order of 100s of millions. I know someone could probably do it for cheaper, but I guess my point is putting an atomic clock in space is expensive. But I also wanted to come back to the cost of operations and "known" satellite position. Because if you need your GPS satellites to have good enough position and time knowledge you need something on the ground with a better than extremely accurate clock. See this picture of the backup clock arriving at the GPS operations center [2] Edit: Also see my comment a couple comments down on my assessment of possible accuracy of the current one-web satellites to get an idea of accuracy. [0] https://en.wikipedia.org/wiki/Galileo_(satellite_navigation) https://en.wikipedia.org/wiki/Galileo_(satellite_navigation) [1] https://www.defense.gov/Newsroom/Releases/Release/Article/2079489/dod-releases-fiscal-year-2021-budget-proposal/ https://www.defense.gov/Newsroom/Releases/Release/Article/20... [2] https://www.schriever.af.mil/News/Article-Display/Article/276171/new-alternate-master-clock-arrives-at-schriever/ https://www.schriever.af.mil/News/Article-Display/Article/27...

dr_orpheus 6y ago

One of the biggest drivers of cost on GNSS satellites is the need for an extremely accurate clock. Position is calculated based on a series of ranges to the satellites with a "known" position. That range is calculated is based on a time-of-flight so you need a very accurate time source. The whole Galileo project cost is 10 billion [0] and this is "cheap" compared to the US GPS system. I can't find great numbers for it, but for the cost of building two new GPS satellites this year is $1.8 billion [1] and operating cost for the existing constellation I believe is on the order of 100s of millions. I know someone could probably do it for cheaper, but I guess my point is putting an atomic clock in space is expensive. But I also wanted to come back to the cost of operations and "known" satellite position. Because if you need your GPS satellites to have good enough position and time knowledge you need something on the ground with a better than extremely accurate clock. See this picture of the backup clock arriving at the GPS operations center [2] Edit: Also see my comment a couple comments down on my assessment of possible accuracy of the current one-web satellites to get an idea of accuracy. [0] https://en.wikipedia.org/wiki/Galileo_(satellite_navigation) https://en.wikipedia.org/wiki/Galileo_(satellite_navigation) [1] https://www.defense.gov/Newsroom/Releases/Release/Article/2079489/dod-releases-fiscal-year-2021-budget-proposal/ https://www.defense.gov/Newsroom/Releases/Release/Article/20... [2] https://www.schriever.af.mil/News/Article-Display/Article/276171/new-alternate-master-clock-arrives-at-schriever/ https://www.schriever.af.mil/News/Article-Display/Article/27...