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from Redwing at lower levels,
as had been expected.
It also confirmed the general accuracy of the Japanese
in their original analysis of the ocean contamination
problem,
even though the levels again were below those
that could cause concern.
The
1958 series of tests,
(Hines,
1960)
Operation Hardtack,
brought more
oceanographic studies of a more sophisticated nature.
In.
addition to the tests over water or on the small islands near
the water,
tests were conducted under water in the open sea and
in the lagoon.
Three vessels were made available for oceano-
graphic surveys,
the U.S.S.
Rehoboth,
a seaplane tender converted
by the navy for oceanographic work, the U.S.S. Collett
and the U.S.S.
Silverstein
(DE 534).
(DE 730),
The Rehoboth was used to
follow the contaminated water mass subsequent to the underwater
detonations.
The data collected provide
some of the most
detailed information on short-lived radioisotopes in the sea.
The data developed aboard the Rehoboth and later,
particularly in analysis of radioisotopic content of
specimens,
revealed certain striking differences in
radioactive composition immediately following nuclear
detonation.
dominant.
The short-lived fission products were
The gamma-emitting radioisotopes in
plankton collected between May 16 and May 20 included
molybdenum 99-technetium 99, with a half~life of
sixty-six hours; and tellurium 132-iodine 132, with a
half-life of seventy-seven hours.
The larger plankton
were found to have ingested larger proportions of