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WAMEMORANDUM FOR RECORD
SUBJECT: =f
de
* Melght ef Ivy (
** pike Cloud
“AL the tine ef the IVY ike Operetion two abrereft designe ted
pee \tshaker® flew rece-track courses, ene due South ef ground sere at
“enpproximetely 7O aautical miles, theether due eset ef ground perc at
~iapprexinately 80 mmutical alles. The planned mission ef these fiights
ams te ecure a photograph of the IVY Mike sleud sech minmte fer ene hour
siafollowing the explosion. This mission was requested by Headquarters UséF,
“SAFOAT~] for eftar-the-fact ¢loud height esleulations but the pictures have
Saat yet been received, and may act be of much velve for the intended pirposs
‘saubeesuse ef poorly defined or absent harizons.
2g +@inecheduled bubble sextant readings were made by —
.-Gin the alreraft te the south and
ef Meadquarters WEAF, APOAT-:
>ain the aircraft te the east.
Alrereft leren pesitions were provided by the
“wmavigator ef the alreraft who alee checked some ef the angle ebservations.
“mkttached hereto is Table I giving the ebservations and esleulations of eloud
diaight and heights ef various ovtstanding features ef the cloud. The obser-
“yetions ef engle, distance to ground sero, and alrereft altitude are believes —
,
*+%0 be euch thet the salculated heights are ast in error ens way or the ether
Aaya Mann a fou thousand feet. Consideretion of seme
would lead
to believe that no large aerrers were introduced by "edge" eighting and
ebtaining erronscusly high angles. First ef all, ‘there can be Litt).
."Sef this kind ef arrcr in sigvting en the rethex sharp-pointed plume which
~“eplelded an altitude of 135,500 feet. The difference between this ati tude
aed the tep of the ¢leud at around 120,000 feet was in the serrect proportic
: age the thickness of the sloud (120,000 ~ 67,000 ® 43,000 feet) as fudge
amt the time.
Secondly, a sighting
on the far right sdge ef the cloud
debe: at 21.75 minutes in Table I) gave 104,000 feet and this ean hardly
fin exror by 40,000 feet dus te erroneous sighting arising fram edge end
thickness effects, os it would be if the cleud did not rise above the trepepeuse. -Thirdly, the mein shear layer measured at 15.25 minutes in Tabis !
agave an altitude cerresponding exactly te that of the prognosticated principi4
‘awehear altitude fer the event and wee again judged te be at the earrect pro:
“portional altitude fer a tep at around 120,000 feet. Fourthly, the altitude:
of 110,000 and 112,000 feet at 2.66 and 3.42 mirartes are not explainebis or
~failse bese line because of latare) movement ef the cloud; sir movements are
not that vepid compared with s plane to ground zero bate line of 66 meutics
miles.
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, SeGuEly INFORMATIO
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