Like her sister vessels—one older ship dating to 1999, two newer ones that entered service in 2009 and mid-2015, plus at least one more Type 815 still under construction—Neptune is roughly 400 feet long. The ship boasts several large domes arranged along the superstructure that apparently house antennae for intercepting radar and radio signals broadcast by the military forces of potential enemies. China’s intelligence analysts at sea and on land can then interpret the signals in order to determine the capabilities of other countries’ ships, planes, and military hardware.