MIT Radiation Laboratory radars

thumb|right|The AN/APN-4 was an airborne LORAN receiver used into the 1960s. It was built in two parts to match the UK's Gee system, and could be swapped with Gee in a few minutes. LORAN (Long Range Navigation) was a hyperbolic radio navigation system developed in the United States during World War II. It was similar to the UK's Gee system, but operated at lower frequencies in order to provide an improved range up to 1,500 miles (2,400 km) with an accuracy of tens of miles. It was first used for ship convoys crossing the Atlantic Ocean, and then by long-range patrol aircraft, but found it

radiometer that measures energy in the one millimetre to meter wavelengths

automatic tracking microwave radar