In addition to the bottom survey. aerial photographs of the crater were t&ken promptly after the snot. In addition, to assist in tracking the boat carrying the fathometer, aerial photographs were taken at 2 min. .ntervals during tne time tne boat was in the crater. The fathometer snowed that tne c-ater had refilled with very ioose sand or mud to a uniform deptn after the shot. In the placement of the barge for Snot <, which was to o+ fired at the same ground zero location as Shot 3, tne H&N group made .ead Line soundings prior to the placement of marxer suoys and moors Pur the barge. The data on those soundings are alsc included in tnis report as evidence of the crater shape. The post-Shot . surve} was condu:ted on the sixth day after the snot. At the time of tne survey, the radiation level 10 ft above the water surface was 25 tc 75 mr/hr. Measirements by other groups demonstrated that tne levels on the lanc arens surrounding the crater were much higher. After the accomplishment oF whe »yost-Snot 1 survey and the preShot 3 and pre-Shot & surveys, a discuss.on was held of the extent of further effort merited in light of tne incertainties as to times and locations of the remainder of the snots In these discussions it was brought out that tne expected result of Shot 3 would be to remove the western end of Tare Island to a deptr a” 50-100 ft. Since the preshot survey of the water surrounding it showed tnat the island had quite steep sides, :t was felt tnat the measurement of the crater would have very small value for the prediction of ‘raters in locations where the earth approached a uniform plane rather tnan a mountain top. In the same discussicn .t was alsc confidenti. predicted that tne result of Shot 4 would te a relatively minor Uist irbance at the bottom. As @ resuit of tuese discussions .% was agreed that a curtailment of effort regarding tne postskhot sirvey of these two shots was appropriate and tne tonclusion was reacne: that adequate data would be obtained if three taut wire runs ccula ve ootained approximating three crater diameters and that these runs oid »e deferred for Shot 3 until after Shot 4. Consequently the prevect group left the forward area on 1 April and returned °c tne forwarc arex on P9 April, immediately after Shot 4, The actus. gostsnot survey cof toe Shot 3 crater was somewhat modified pecause tne vield was micr sma lier “han had been predicted and hence the crater, instead of ensompassing all of the western end of the island was mich nearer to being .andlocked within the western end of the island. In acceding t. *ne cressure of the continuing shot schedule for CASTL:, .t was decidec not the pnotograpnict airplane was quipment for the postsnot measurement. been predictes t:e Lancmarxs availanle were inadequate. in addition, ceca. existent. tu vceestablish tne Raydist e- *.r Shots * and 4, and as had ‘or v.sual location of the ship 7? tre tight shot scnedule then uct apnle to rendezvous with the boat to assist in tne Location during t.c fathometer surveys. Consequently tne crate: dimensions were ijieve mined first by the fathometer wire equipment and later by equipment on the ¢ nip combined with ta. serial pnotograpn.i: mapping tecnoni,.e.. In actual operation it was found extreme>. U'ficult to mane ve: S * # 1,7! in the narrow confines aa dks, tow NO te »t nee