pattern was negative.
at 0941, 1033,
Subsequent reports at the south end of the pattern
1038 and 1057 indicated contamination of 0.05 to 0.10 R/hr.
This was undoubtedly the lowest portion of the stem since it was encountered within minutes of the time forecast by the preshot air radex area
and hodograph.
At 1219, radiation levels of approximately 2 R/hr were
reported by Wilson 3 at the north end of the pattern;
it is believed that
this was some of the same fallout encountered by Wilson 2
low).
One significant difference was noted, however,
(discussed be-
in that Wilson 3 re-
ported the simultaneous collection of a "white frost or snow” on the front
of the aircraft.
At this time, the aircraft was ordered to the south end
of the pattern to “cool off."
The frost-like material was washed off when
the aircraft passed through a rain shower while responding to the order,
and the aircraft's radiation background dropped markedly.
Subsequent read-
ings in the pattern were background, and at approximately 1430 Wilson 3 was
ordered to attempt to locate the southern edge of that portion of the cloud
believed to be moving west-northwest.
It was suggested that Wilson 3 pro-
ceed from the holding pattern to 12.5°N, 163°E and thence to Enewetak. No
contamination was reported on this phase of the flight, which indicated
that cloud movement was more northerly than had been presumed.
Wilson 2 was directed to fly in the holding pattern from H+2 to H+5,
then search a sector east of ground zero (limiting bearings 60° and 90°
true).
The first contact with the cloud was reported by Wilson 2 at 1118
at the north end of the racetrack pattern, with the radiation level reported at 0.850 R/hr.
This was probably fallout from the southwesternmost
edge of cloud segments that were moving north.
Wilson 2 did not encounter
contamination at the southern end of the pattern.
Wilson 3, however, 5,000
feet (1.52 km) lower, reported radiation from approximately 0900 to 1100
{establishing an upper limit of about 8,000 feet [2.45 km] for cloud segments moving in a southwesterly direction and confirming both the air radex area and the hodograph).
Immediately after the initial cloud contact,
Wilson 2 proceeded east toward the previously designated search sector.
At that time, however, the Radsafe Office desired additional information
concerning any possible cloud movement toward Enewetak; accordingly,
260