AERIAL PHOTO AND RADIOLOGICAL SURVEY FROGRAM
2.
RADIOLOGICAL SURVEY
The Aerial Radiation Surveys will be carried out by means of two
Navy helicopters which will fly cultiple missions from the USNS
WHEELING station near the atoll or in the lagoons wnen possible.
EG&G will supply the scientific flight crews and technical support
personnel to operate and maintain the radiation measuring and
position measuring equipment.
The aerial radiation survey will employ an array of forty 12.7 cm
diameter by 5 cm thick NaI(Tl) scintillation detectors mounted within
two pads which are hung externally on the helicopter.
Signals from
the detectors are fed into a multichannel data acquisition system
mounted inside the helicopter.
Gamma radiation data is accumulated
continuously and recorded on magnetic tape once each second.
in
addition to the radiation data, position information provided by a
microwave ranging system and a radar altimeter are also recorded on
magnetic tape each second.
Flight lines on each atoll island spaced
45 meters apart will be flown at an altitude of 30 meters and a speed
of 30 meters per second.
A steering indicator,
using signals from the
microwave ranging system, will be used to aid the helicopter pilot in
maintaining uniform flight line spacing.
A large portion of
the data reduction will be performed in the field
using two NOVA 840 minicomputer based data reduction systems.
Radiation
and position data are correlated on a second-by-second basis and processed
in the form of radiation contours overlayed on aerial photographs.
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