early moments subsequent to time zero.
Later pictures show the shock wavealong the
water surface as it progressed outward from site zero.
,
To extract IBDA data from the photographs, large-scale graphics were prepared to
achieve greater accuracy in interpretation.
Site zero was established within an accuracy
of 600 to 1,100 feet from the actual location by determining the center of curvature for
the horseshoe configuration.
Interpreters attempted to obtain yield data from the photo-
graphs by utilizing time-distance curves that indicate the progress of the shock wave
TABLE 6.7
AIRCRAFT POSITIONS
Smot
i
2
3
34,000
15
33,000
18
32,000
12
31,000
23
31.000
23
30,006
30,000
4
8
6
_
—_
32,000
15
32,000
12
31,000
20
31,000
23
—
_
31,600
20
30,000
30 ,000
30,060
30 ,000
B-60 No. 1
Altitude, ft
Distance, naut mi
B-8C No. 2
Altuude, ft
Distance, naut mi
B-50 No. $
Altitude, ft
Distance, naut mi
30
30
27
30
30
37
outward from ground zero for various yields. Computations of yield by this method
proved inaccurate. Since participation was limited to surface bursts, no attempt was
made to obtain height-of-burst information.
6.4
IONOSPHERE STUDIES
Project 6.6 was conducted to study the effects of megaton-yield-range detonations on
the ionosphere
Following Shot Mike of Operation Ivy, it was noted that the virtual height
of the F~2 layer greatly increased. The project desired to corroborate this phenomenon
and to study the cause-and-effect relationships associated with it. It was also desired to
obtain data on effects at large distances from the detonation to ascertain the possibility
of using such effects as a means of long-range detection.
For collection of data, two ionosphere recorders were operated in the Marshall Islands:
one at Parry Island 200 miles west of Bikini and the other at Rongerik Atoll 150 miles
east of Bikini.
In addition, normal data from existing stations at Maui and Adak and
special data from existing stations at Guam and Okinawa were studied to determine ef-
fects at distances of 1,400 to 3,000 miles.
At Parry Island, severe absorption occurred for several hours following all megatonyield shots. This phenomenon wasattributed to ionization resulting from radioactive
particles carried to the west by fast winds at altitudes of 60,000 to 120,000 feet. Turbulence in the E-region after megaton-yield shots was manifested by sporadic E-returns
detected at Rongerik. In the F2 layer, an effect similar to that observed during Ivy was
noted, but its nature varied from shot to shot. Apparently the movement of electrons in
this layer was far more complex than originally assumed, but was still attributable to
& large-scale convection resulting from the conversion of blast-wave energy into heat
in the upper atmosphere.
Data from the distant stations indicated that ionospheric disturbances were propagated
up to 2,600 miles from the points of detonation at velocities between 8 and 16 km/min.
It appeared that the duration of the disturbances was related in some manner to the yield
of the device and was about inversely proportional to the distance.
91