Shot Doppler was the 13th atomic test of Operation Plumbbob, detonated on 23 August 1957 at 5:30 a.m. PDT from a balloon at 1,500 feet above the Nevada Test Site. It was a Los Alamos Scientific Laboratory gas-boosted implosion device, a possible development test of the XW-34 warhead, producing 11 kilotons — consistent with its predicted performance. The device was compact: 17 inches in diameter, 26 inches long, with a total weight of just 275 lb. This Lookout Mountain Laboratory photograph — AEC-57-5829 — captures the cloud immediately after detonation, the mushroom cap fully formed and luminous against the pre-dawn darkness, the stem still thick below it. At ground level the base surge of disturbed desert soil is visible. Doppler is named for Christian Doppler (1803–1853), the Austrian physicist who described the relationship between wave frequency and the motion of its source — the LASL convention of naming shots for deceased scientists.