It's not just launches. It's, well, everything. It drives me nuts!

Spacecraft flight software almost always have the capability to execute uplinked commands based on time. But what time scale? The operational control systems for spacecraft almost always have the ability to issue timed commands to spacecraft. But what time scale? The various mission planning and analysis systems also are time dependent. But yet again, what time scale?

Some systems support TAI as well as UTC. Others support GPS time as well as UTC. Yet others only support GMT (Greenwich Mean Time), which hasn't existed since 1973. A tiny few support relativistically-correct time scales as well as UTC. The ubiquitous answer is UTC (or GMT in the case of legacy systems from some previous millennium). So, rather sadly, this is the one time scale that is almost always used.

This sadly means that spacecraft should not doing anything critical near a leap second boundary.

It's not just launches. It's, well, everything. It drives me nuts!

Spacecraft flight software almost always have the capability to execute uplinked commands based on time. But what time scale? The operational control systems for spacecraft almost always have the ability to issue timed commands to spacecraft. But what time scale? The various mission planning and analysis systems also are time dependent. But yet again, what time scale?

Some systems support TAI as well as UTC. Others support GPS time as well as UTC. Yet others only support GMT (Greenwich Mean Time), which hasn't existed since 1973. A tiny few support relativistically-correct time scales as well as UTC. The ubiquitous answer is UTC (or GMT in the case of legacy systems from some previous millennium). So, rather sadly, this is the one time scale that is almost always used.

This sadly means that spacecraft should not be doing anything critical near a leap second boundary.