North Korea has used images to project strength and signal developments in its nuclear program, and the images have helped experts understand whether the country could hit the United States with a nuclear weapon.

A photograph released this week by the Korean Central News Agency, the North’s state news agency, shows a beaming Mr. Kim surrounded by military officers and was reportedly taken at the launch site, a clear sign of his personal involvement in the exercise.

If the smile on Mr. Kim’s face does not clearly indicate his pleasure with the country’s latest “muscle flexing,” as K.C.N.A. put it, the agency made clear that he “expressed great satisfaction over the successful launching.” The test was part of a broader plan for “containing Guam,” a United States territory in the Pacific.