During the late 1940s, NRL foresaw the need to detect moving targets, including aircraft and missiles, at distances and altitudes beyond the line-of-sight. NRL began to investigate the use of radar operating in the high frequency (HF, or short wave) portion of the radio spectrum to extend the range beyond the horizon. By 1955, NRL was operating a low-power HF radar system called Multiple Storage, Integration, and Correlation (MUSIC). Using signals reflected by the ionosphere as well as by the target, MUSIC allowed the detection of missile launches at distances up to 600 nautical miles and of atomic explosions at distances up to 1700 nautical miles. A much improved system called Magnetic-Drum Radar Equipment (MADRE) was developed in 1961 and was installed at NRL's Chesapeake Bay Detachment.