New commercial satellite imagery of the Punggye-ri Nuclear Test Site from March 25 shows the continued presence of three to four vehicles or equipment trailers at the entrance to the North Portal. The texture of the ground from the portal entrance past the vehicles or equipment trailers suggests that communications cables may have been laid on the ground. This equipment would likely be used to initiate the test, collect data from the explosion and process the data. Also notable, water is being pumped out of the portal and draining downhill to the east and west, presumably to keep the tunnel dry for monitoring or communications equipment.
The combination of these factors strongly suggests that test preparations are well underway, including the installation of instrumentation. The imagery, however, does not provide any definitive evidence of either a nuclear device or the timing of a test.
Apart from several mining carts at the West Portal, there is no significant activity at the other areas of the test site. The lack of activity may mean that test preparations are in their final stages. However, since North Korea knows the world is watching and is capable of deception, caution should be used before declaring that a nuclear test is imminent.
Figure 1. Probable cabling and water drainage seen at the North Portal.