True. It's a contrived example. But people easily forget just how fast light travels. 1 nanosecond is just about 1 foot.

I figured the on board clocks received updates from the ground... I'm guessing the ephemeris is updated from the ground too. But the onboard clock accuracy improvement is still important. I wonder if the improved accuracy allows for either fewer updates, or better accuracy if ground based updates are... interrupted... for some reason. <img src="/images/graemlins/frown.gif" alt="" />