5. United States and Japanese maps will be used to determine the dis - tance from the cameras to the barge. 6. The Observers will be shown the cameras to be used in photograph- ing the fireball. ured. The focal length of the lenses in the cameras will be meas- The timing device which correlates the fireball images with the time after detonation will be calibrated by using 200-cycle tuning forks. The Ob- servers will view the selection of the filter paper to be installed in the sampling equipment which will be flown through the residue cloud of the explosion. They may also inspect the sampling equipment to be used. 7. The time at which the sampling aircraft takes off will be fixed rough- ly by the requirement that the people engaged in the sampling flight shall receive no more than one roentgen of radiation. The Observers will attend the flight briefing in which the flight plan is formulated. Upon return of the air- craft, the filter paper containing the radioactive residue will be removed by remote control and stored in a sealed container. 8. The films of the fireball will also be placed in sealed containers. 9. The filter paper container and the film containers will accompany the Observers to Berkeley for analysis. 10. In Berkeley the Observers may participate in the radiochemical analysis described below for determining the fission yield of the bomb. The Observers may also participate in the development of the fireball films. Duplicate film strips will be made available to the Observers for their re- tention. The dimensions of the fireball images will be measured on a com- parator. The Observers may subsequently verify those dimensions on their own instruments. 11. The fission ratio of the bomb Fission yield in megatons Total yield in megatons will then be established. 12. The Observers should be prepared for a possible delay of several days in the detonation of the device.