North Korea appears to have resumed "pop up tests" at Sinpo. This a big deal -- but one of those cases where we may have to wait. A short thread. Well, not that short. 
In a pop-up test, a missile is ejected from a canister or a silo using compressed gas. The missile either has no propellant, the propellant does ignite or it burns for only a very short time. This is step precedes flight testing of the missile.
tass.com/defense/1014008
tass.com/defense/1014008
North Korea has a pop-up test stand at Sinpo. This image, probably from April or May 2016, shows the support structure, a canister held up with an erector arm, and the nose of a missile that was ejected. (There was similar stand near Kusong, but North Korea dismantled it.)
We don't have video of a North Korean test, but here is an American one for fun. 🍿
@planetlabs imaged Sinpo twice on April 5, capturing activities suggestive of a pop-up test. @38NorthNK published the afternoon image, but the morning image shows more -- not only is the support structure pulled back, a big crane is present and the erector-arm is vertical.
We can see the progression of activities at the site on April 4-5. Situation is normal on April 4. On the morning of April 5, the support structure is pulled back, a crane has appeared and the arm is up. By the afternoon, the big crane seems gone and the arm is back down.
We saw similar signatures in May 2017 before a round of pop-up tests in North Korea. @planetlabs imaged cranes on site on three days in the month preceding a May 31 pop-up test. North Korea ended up doing 4 pop-ups in 2017, probably for the Pukguksong-3.
So what's (popping) up? One possibility is that North Korea is in the very early stages of testing a new missile that will be launched from a canister. We have seen some enigmatic canisters in North Korea before.
Still, it could be months before North Korea finishes pop-up testing at Sinpo, then months more before it flight tests whatever is under development there. A cool thing about OSINT is that we catch glimpses of the future. The downside is that we often have to wait. /end
