New satellite photos from April 29, 2012 indicate that a major upgrade of North Korea’s Tonghae Satellite Launching Ground—more commonly referred to as Musudan-ri—underway since summer 2011, is making rapid progress. The new construction is intended to support future launches of rockets larger than the recently tested Unha—more capable liquid fueled space launch vehicles or missiles with intercontinental ranges—that will also overfly Japan, further aggravating regional tensions. In addition to a new launch pad under construction, much of the nearby village of Taepodong has been razed to clear the way for what appears to be a new building designed to assemble larger rockets. The high bay portion of that building—the area where rockets are assembled—may have twice as much floor space as similar facilities at Musudan-ri and the new Sohae Satellite Launching Station (commonly referred to as Tongchang-ri). At the current pace of construction, the facilities should be operational by 2016-17.
The new assembly building is somewhat similar to one at Iran’s Semnan Missile and Space Center. Nevertheless, while the two countries have a long history of missile cooperation, it is too soon to tell whether that cooperation extends to the design and construction of this facility or the new long-range liquid fueled rocket.
Probable New Rocket Launch Pad
Based on previous satellite imagery, construction at the test range began in summer 2011 with ground clearing visible that fall. Over the past eight months, work has proceeded at a fast pace. The new launch pad, seen in an April 29, 2012 satellite photograph from DigitalGlobe, is still in the early construction phase (see figure 1). The site is located in a remote area a little less than one kilometer northeast of the original rocket motor test stand and 1.75 kilometers due east of the original launch pad. 
Present are a flame trench orientated slightly downhill toward a stream, foundations for fuel and oxidizer tank buildings that bracket the flame trench, a dam up-stream connected by a pipeline to a water tank at the main facility and three other completed buildings. The most unusual feature is a white circular structure that surrounds where the rocket will stand when erected on the pad, the purpose of which is unclear.
Figure 1. New probable launch pad under construction at Musudan-ri (Tonghae Satellite Launching Ground).
Three developments strongly suggest that this new pad is designed to launch rockets larger than the recently tested Unha, either more capable, liquid fueled space launch vehicles or missiles with intercontinental ranges. (Figure 2 is an enlargement of the main area of the new facility.) First, the flame trench—the dark object in the center—is larger than those at the original Musudan-ri launch pad and the new Tongchang-ri. The new trench measures 33 meters in length, 9.5 meters wide, and 6 to 8 meters deep. The circular ring—with an outside diameter of 14.5 meters and an inside diameter the same as the tranche’s width of 9.5 meters—marks the beginning of the pad. (A crane can be seen outside the ring). A white object inside the ring is probably the end wall of the trench.
Figure 2. Enlargement of the launch pad area.
Second, just above the ring are four concrete footings. Their location indicates that they are for a new rocket gantry rather than a tower for a new engine test stand that would be built over the trench. Based on the distances between the footings—14.5 meters apart with widths of 9.5 meters—the new gantry will be larger than the structure at Tongchang-ri, at which, the footings measure 10 meters by 8 meters. That gantry easily accommodated the Unha rocket and was clearly designed to launch even larger rockets.
Finally, buildings designed to enclose the fuel and oxidizer tanks as well as to contain five tanks each, are located on each side of the pad area and measure 23.5 by 18 meters. They are larger than two largest propellant buildings near the launch pad at Tongchang-ri—24 by 13 meters and 21 by 13 meters. Once again, since previous 38 North analysis  of Tongchang-ri concluded that it was built to accommodate a space launch vehicle larger than the recently tested Unha, these new buildings could support the launch of a rocket “at least” as large as that larger rocket.
In summary, the large flame trench, probable gantry tower, and size of the fuel and oxidizer buildings strongly indicate the construction of a launch area for a large liquid fueled rocket. These features coupled with the fact that the existing pad at the test range is not capable of launching a rocket bigger than the Unha strongly suggests the North plans to use its eastern test range for future launches of large liquid fueled rockets. Aside from the obvious security implications ofNorth Korea’s continued development of longer-range rockets, these tests will overfly Japan, further aggravating tensions between Pyongyang and its neighbors.
Probable New Rocket Assembly Building
The second major construction project—due east of the test range motor pool—required the razing of about 70 homes, 5 larger buildings, and many sheds in the village of Taepodong. (Figure 3 shows the area in late April 2010 before the buildings were torn down.)
Figure 3. The village of Taepodong before the new construction.
Figure 4. Probable new missile assembly building in an early phase of construction.
Construction of the new facility also started in the summer of 2011 with the clearing away of the old buildings. (Figures 4 and 5 show the new construction and an enlargement of the area). The foundations for a large T-shaped structure measure about 25 by 70 meters, and increases in width to 35 meters along each side. The T foundations at the eastern end measure 23 by 54 meters. It appears this building will be connected to the new launch pad (about 1.86 kilometers away) by a road under construction. (In figure 4, a bulldozer can be seen near the lower road in the right corner of the image that will connect the two facilities.)
The probable missile assembly building is bigger than similar existing facilities at Musudan-ri and Tongchang-ri, allowing it to handle even larger rockets. A comparison of the floor space in the high bay section of these buildings—the area where the rocket is brought into the building in stages and assembled—and other administrative/laboratory space is as follows in square meters:
|High bay floor space||Other space|
|Tonghae new building:||1750||1592|
|Tonghae old building:||864||874|
|Sohae existing building:||864||1387|
It may seem unusual that the North would build a missile assembly building in a location that requires the razing of a significant portion of the village of Taepodong. However, civilians may no longer be located in the area. Moreover, aside from the fact that the old building is incapable of supporting the assembly and checkout of a rocket larger than the Unha, it may also not be in an optimum location to serve the new launch area. The high bay area is twice as big as the other structures; the overall increase in floor space may reflect the reality that the old assembly building will not be adequate to process the new larger rocket. In the future, the existing assembly building at Tongchang-ri may have to be replaced since it has the same amount of square footage in the high bay space as the old facility at Musudan-ri.
Figure 5. Early construction of a large probable missile assembly building.
Figure 6. The New Facilities at Musudan-ri (in Google Earth)
Google Earth programming done by Curtis Melvin and Tamara Patton.
An Iranian Connection?
At this early stage of construction, while it is difficult to find clear signs of North Korean-Iranian cooperation, the new facility is somewhat similar to a recently completed horizontal assembly building at Iran’s Semnan launch complex, also intended to handle a new large liquid fueled rocket. Measuring 100 by 50 meters with a center high bay section 60 by 38.5 meters, the Iranian building is larger. (Its high bay floor space is about 2310 square meters and other space 2490 square meters.) The North Korean facility, however, seems to have a similar layout, with labs and what appear to be administrative offices on the sides of the high bay building. But there are also clear differences; for example, the “T” building at the end of the North Korean structure is not present in Iran.
While the extent of North Korean-Iranian collaboration on a new long-range liquid fueled rocket that both appear to be developing remains unclear, such cooperation would not be out of the question since the two countries have worked together on most of their ballistic missile and space launch vehicle development in the past. As construction progresses on the new North Korean facility, careful examination of further satellite photography will be warranted to discern possible new signs of cooperation.
Satellite imagery analysis provided by Nick Hansen, an imagery analyst and foreign weapons expert. See more articles by Nick here .
  The coordinates for this facility are 40° 51’ 29.5″N, 129° 41′ 10.55″E.