TEST B: UNDERWATER EXPLOSION 



array were the unmanned drone boats, controlled by 

 radio signals sent from support ships located well out 

 of danger. These boats threaded their way through 

 the array of ''hot" ships, taking w^ater samples and 

 recording just how intense the radioactivity was in 

 each area. Manned boats skirted the region cautiously, 

 keeping outside of the really ''hot" zones. 



Master charts were prepared on the support ships 

 showing danger areas. A "red line" was drawn show- 

 ing where the radioactivity exceeded one roentgen per 

 day, and was thus unsafe. A "blue line" indicated 

 where the activity was less than 0.1 roentgen, and was 

 safe. As the lagoon currents slowly spread, shifting 

 the contaminated water area, new charts were prepared 

 and word sent to all ships.* 



All animals had been taken off the target ships by 

 five days after B-Day; some of the scientific instru- 

 ments could not be approached with safety for weeks 

 afterwards. 



* Re-entry of the target area would have been greatly slowed if 

 previous studies of lagoon currents had not teen made. Commander 

 Roger Revellers Oceanographic Group, besides making model 

 studies, had spent weeks finding just where the lagoon currents 

 went, and how fast. With dye markers, floating poles, and other 

 equipment his group tracked not only the surface currents but also 

 the counter -currents flowing along the lagoon bottom. They found 

 where the bottom water welled up, and where the surface water de- 

 scended. They found how the current changed with wind and 

 tide. Thanks to this information, they could assure the Task Force 

 Commander that advance scouts would not suddenly find them- 

 selves trapped by radioactive water welling up behind them un- 

 expectedly. 



69 



