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HEADQUARTERS USAF
OFFICE FOR ATOMIC ENERGY ,DCS/C
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glté 1453
24 April 1953
4 MAY 1953
MELORANDU:; FOR RECORD
sect: MMR Height of IVY (Rggggg ike Cloud
le
At the time of the IVY Mike Operation two eircraft designated
“Saltshaker” flew race-track courses, one due south of ground zero at
approximately 70 nautical miles, the other due east of ground zero at
epproxinctely 60 nautical miles.
The planned mission of these flights
was to secure a photcgraph of the IVY Mike cloud each minute for one heur
folloving the explosion. This mission was requested by Headquarters USAF,
AFOLT-1 for after~the-fact cloud height calculations but the pictures heve
not yet been received, and may not be of much value for the intended purpose
becouse of pocrly defined or absent horizons.
2,
Unscheculed bubble sextant readings vere made by Dr. ft. D. Urry
in the aircraft to the south and Colonel Fee of Headquarters USAF, AFUAT-]
in the aircraft to the east. Aircraft loran positions were provided by the
nevigator of the aircraft who also checked some cf the angle observations.
Attached heretc is Table I giving the cbservations and calculations of cloud
heisht end heights of various outstanding features of the cloud.
The obser
vetions ef angle, distance to ground zero, and aircraft altitude are belicved
tc be such that the calculated heights are not in error one way or the cther
by mere than a few thousand feet.
Consideration of some points vould lead
one te believe that no large errors were introduced by “edge” sighting and
thereby obtaining erroneously high angles. First of all, there can be little
ef this kind cf error in sighting on the rather sharp-peinted plume which
yielded an altitude of 135,500 feet. The difference between this altituce
and the top of the cloud at around 120,000 feet was in the ccrrect propertion
to the thickness of the cloud (120,000 - 67,000 = 43,000 feet) as judged
at the tire. Seccndly, a sighting on the far right edge of the cloud
(cbs: at 11.75 minutes in Table I) gave 104,000 feet and this can hardly be
in error by 40,00 feet due to erroneous sighting arising from edge and
thickness effects, as it would be if the cloud did not rise above the tropofeuSsce Thircly, the main shear layer measured at 15.25 minutes in Table I
géve an altitude corresponding exactly to that of the prognesticated princi
shear altitude for the event and was again judged toe be at the ccrrect properticns] altitude fer a top et around 120,000 feet. Fourthly, the altitudes
ez 116,000 and 112,000 feet at 2.66 and 3.42 minutes are not explainable on
false base line because of lateral movement of the cloud; air movements are
net that rapid compared with a plane to greund zerc base line of 68 nautical
rN.
rles.
Inclosure ) 1
Copied/DOE
LANL, J-Div.
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