I should have been more clear. GPS is the source, but the APIs that these systems use with the ground are usually UTC due to the nature of the clock source on t

I should have been more clear. GPS is the source, but the APIs that these systems use with the ground are usually UTC due to the nature of the clock source on the servers they are talking to. Getting a UTC time from GPS involves the leap second and during the event agreeing how how it’s implemented. Some systems smear, some double tick a 0 at midnight, it’s a disaster. I completely agree that any coordination should be TAI. But that’s not the world we have to interface with unfortunately. This hell isn’t imaginary, I’m speaking from experience of seeing stuff fall out of sync on the last leap second due to some systems using GPS with no smear and others using NTP to a source that smears.