In 2006, the U.S. Air Force acquired and installed a new lightning detection system that provides the times and three-dimensional positions of emission sources from lightning at VHF frequencies. The primary purpose of this system, called the Four-Dimensional Lightning Surveillance System (4DLSS), is eventually to replace NASA's aging LDAR (Lightning Detection And Ranging) system. The secondary purpose of 4DLSS is to integrate the analysis of the data from the Cloud to Ground Lightning Surveillance System sensors onto the same processor. This faster processor will allow the detection and display of all return strokes in real time, as opposed to just the first return stroke. Recent research has shown that many cloud to ground lightning flashes have return strokes with multiple ground attachment points separated by several kilometers, and therefore detecting and displaying all return strokes is important to safety. Integrating the processing onto a newer common processor will also ease future maintenance and upgrades. The purpose of this paper is to describe the new system, its operational uses and applications, and the performance testing that has been done to validate the new system. This performance testing consists of detection efficiency and location accuracy validations against the operational LDAR network as well as model estimates of the new system's performance.