In 1954, the fallout plume from the Castle Bravo nuclear test passed over Bikar about 20 hours after the shot. Based on ash from plant samples taken on March 9, the atoll was contaminated by about 1,400,000 d/m/gm of radioactive material, compared with 35,000,000 d/m/gm from the most contaminated soil samples at Rongelap Atoll, and 950 d/m/gm at Majuro Atoll, several hundred miles south of the fallout pattern. This experience led to a pre-planned aerial survey of atolls adjacent to the subsequent March 27 Castle Romeo test, timed at one and four hours after the shot. The aircraft were equipped with gamma radiation detectors designed to measure ground contamination from altitudes of 200 to 500 feet. An overflight of Bikar Island measured 0.1 mrem/hr (1 μGy) an hour after the shot, rising to 15 mrem/hr (150 μGy) three hours later.