Vapor BEST AVAILA"E Copy Operations: To measure sea waves generated by MIKE, instruments were set out at 19 locations: the Enewetak Lagoon near Runit and Enewetak Island, Sea Mounts 265 and 72 north of ground zero, two locations on Bikini Atoll, Kwajalein, Wake, Truk, Guam, Canton Island, Yap, Midway, four locations in Hawaii, and two locations in California. The Horizon recovered the instruments from the two sea mounts. Radiation Exposure Potential: The Horizon placed instruments on the two sea mounts before the MIKE shot. At shot time the ship “was standing by Sea Mount 72. At 0745 the ship was ordered-to get underway on a course 045°T at 11.5 knots for 4 hours and then started circling on new station approximately 100 miles north-northeast of ground zero. At 1240 radioactive fallout was detected and the ship was closed up, ventilation secured, and the washdown system started. Upon receipt of a message from the Horizon that fallout was being encountered, the ship was ordered to proceed southward. After 25 hours steaming at 11.5 knots, the ship reported clear of the fallout area and that the peak radiation intensity encountered was an average of 0.008 R/hr (gamma only) and a maximum of 0.035 R/hr (gamma only). After Ola) o4¢,. from the washdown system were hosed down and the ship's decks were washed down. Then the radiation levels decreased to an average of 0.003 R/hr, with a maximum of 0.020 R/hr. When the ship the returned to Enewetak on 6 November, the radiation intensity had lar f\ Ihe Ob Ve. py leaving the areas of highest activity, the masts above the spray 4-58