In just 42 seconds, a small Chinese satellite captured images of a large area around a US city that would be sharp enough to identify a military vehicle on the street and tell what type of weapon it might be carrying, say scientists reporting on the breakthrough.

Beijing-3, a small one-tonne commercial satellite launched by China in June performed an in-depth scan of the core area of the San Francisco Bay (3,800 square kilometres or 1,470 square miles), according to scientists involved in the project.

Most Earth observation satellites must be stable when taking images because attitude control mechanisms can produce vibrations that blur the images. But in this experiment on June 16, the Beijing-3 rolled and yawed wildly, the dramatic motion changing the angle of its camera’s line of sight to the ground when flying over North America. The movement allowed it to capture a larger area than satellites have managed until now.