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 sat

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...