It may mean the mission has started successfully, but it can also mean it’s OK for the mission to start because there are no obstacles. Let’s imagine a war movie, where a group of soldiers is waiting for headquarters to send them out on a mission. The commander runs in and says “the mission is a go!” — that would mean it’s OK to leave and start on the mission.
It means the mission has started
You may have heard the term: “All systems go!” which means
basically the same thing, all is in readiness to begin the mission.
I think it goes back to the days of early space exploration at NASA, There were banks of flight technicians at Houston who monitored various functions of the rockets. Before a step was taken – for example lighting the rocket – the flight controller would turn to each one in turn and ask them for a decision whether to go ahead or stop the countdown. Each in turn would reply “go” (or “delay”). If the controller received all positive responses he would say “the mission is a go”. That signified a collective decision to proceed.
It means the mission has been accepted, or has been started.(:
Basically the mission has started/commenced/begun/etc…
Source(s): You’ve been watching mission impossible, haven’t you…