 The radars have been modified and adapted to meteorology and then delivered at the rate of five per year.The modifications were conducted by the weather service and the modified radars took the successive names of WSR-1, WSR-1A, WSR-3 and WSR-4, depending on the gradual improvement of hardware.The first WSR-1 was put into service at the Washington, DC, national airport on March 12, 1947.