With underground railways, giant tarps and a movable launch pad structure in place, experts say, the North is getting a lot better at concealing its preparations.
American and Japanese officials say they are seeing heightened activity at North Korea's main rocket facility, though they stress it's still unclear if a launch really is in the works or how soon it might come.
Intelligence officials in Seoul, stung by their failure to predict the North's January 6 nuclear test, are also cautiously warning another provocation could happen abruptly.
There are indications -- including the construction of a new and taller gantry, visible in commercial satellite imagery -- that it could be a bigger and better version of the Unha 3 space launch vehicle that lifted off from the Sohae facility in 2012, on the west coast of North Korea.
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That would be in line with the North's own previous announcements.
The Unha 3 successfully delivered North Korea's first satellite into Earth orbit. A January 2013 report by Rodong Sinmun, the ruling party newspaper, which has since been deleted from its online edition, quoted a scientist saying there would be a series of launches of observation and communication satellites culminating with Unha 9, which would carry a lunar orbiter.
Models of the larger and much more formidable-looking Unha 9 rocket have since been displayed at various events in North Korea, including annual flower shows held in honour of national founder Kim Il Sung and his son, Kim Jong Il.
Although there are important differences, the US and others have strongly criticised such rocket launches because similar technologies can be used in the development of ICBMs, which North Korea is banned from doing under UN restrictions.
Tightening its punitive squeeze on the North, the US on January 17 announced sanctions on 11 individuals and entities involved in Iran's ballistic missile programme, including Iranian officials it said had direct links to North Korea and work being done by Pyongyang on "an 80-ton rocket booster."
It said two of the sanctioned Iranians "have been critical to the development of the 80-ton rocket booster, and both travelled to Pyongyang during contract negotiations."
Whether the booster would be a new first stage for the Unha rockets or something different is not known.