North Korea appears to have conducted a rocket engine test at its main spaceport in July, possibly to troubleshoot the launch vehicle that failed to put a military satellite in orbit in late May and prepare for the next attempt, according to NK Pro analysis of satellite imagery.

Planet Labs imagery suggests the test took place at the vertical engine test stand inside the Sohae Satellite Launching Ground complex between July 7 and 16. It comes as construction and upgrades have continued in recent weeks around the entire Sohae complex.

The clearest sign of an engine test