The tests, the most recent in mid-September, appear to have been of liquid-fueled, first-stage engines for either the Unha-3 satellite launch vehicle or the KN-08 long-range missile first displayed during a parade in Pyongyang in April, the 38 North blog of the U.S.-Korea Institute at Johns Hopkins University said.
Even though the rocket test failed last spring, commercial satellite imagery indicates North Korea is still developing long-range missiles, possibly with intercontinental ranges, the blog said.
Also, satellite imagery of the Sohae Satellite Launching Station rocket launch area indicates construction activity that would be necessary for future launches of long-range rockets larger than either the Unha-3 or the KN-08, the blog said.
38 North said the U.S. and South Korean presidential elections may spur North Korea to undertake new activities in 2013, including rocket and nuclear tests that would contribute to development of its nuclear deterrent. The blog said whether testing large rocket motors or construction activity at the launch pad would play a role for future activities remained unclear.