I don't think relativistic effects are that great of a problem; I'd imagine that we know the orbital and gravitational characteristics well enough to do pretty

I don't think relativistic effects are that great of a problem; I'd imagine that we know the orbital and gravitational characteristics well enough to do pretty decent compensation for relativity. That being said, nanosecond accuracy might be out of our reach, considering that it's bit of a challenge to get that level of accuracy on even on Earth. Also shipping atomic clocks to space is not all that outrageous idea. Few years ago NASA lauched Deep Space Atomic Clock[1], which is exactly what it sounds like. Also modern "chip scale" atomic clocks[2] are pretty small and low power, so I would not be surprised to see those in future missions. [1] https://www.nasa.gov/mission_pages/tdm/clock/index.html https://www.nasa.gov/mission_pages/tdm/clock/index.html [2] https://www.microsemi.com/product-directory/embedded-clocks-frequency-references/5207-space-csac https://www.microsemi.com/product-directory/embedded-clocks-...