Still, North Korea has never tested an ICBM, so there is a fair amount of educated guessing going on in and outside of several governments about when, where, and how North Korea might make its debut. The easiest way to find out would be if North Korea issued a notice to airmen, known as a NOTAM. The idea behind a NOTAM is to warn sea and aircraft of potential hazards during the flight time of the rocket. The North Koreans have done this before for their space launches, but not for their missile launches. North Korea, if you read The Atlantic, I strongly recommend that you issue one in advance of an ICBM test. By giving advanced warning, you are making it clear that you are starting a test and not restarting a war.
But North Korea is not a very trusting state, so its leaders may not issue a NOTAM for fear the U.S. or South Korea might strike the missile before it launches. There’s been a lot of talk in the U.S. about doing just this, though it is another quick way to restart a war.
Without a NOTAM to tip off observers that a launch is imminent, the next way to know what’s happening is to turn to satellite imagery. Those of us in the open-source world use commercial satellite imagery companies like Planet to get near-daily updates. Where does one start to look? One possibility is that the North Koreans will not use a transporter erector launcher (TEL) truck of the kind visible in parades, because they are scarce and it would be too damaging to the ICBM program to lose one in what will likely be a failed first test. That makes Sohae a possibility. The satellite launch site there conveniently already has everything one would want for a test—a gantry tower for stabilizing the missile, fuel, oxidizer, engineers, and communications that make it easy for Kim Jong Un to observe from afar in case of failure or preemptive strike.