ELECTROMAGNETIC RADIATION CALIBRATION
OBJECTIVES
In order to gain maximum information on nuclear detonaticns as
determiried from the electromagnetic pulse received at distances, there
are two fundamental problems; first, the discrimination of nuclearweapon pulses from natural atmospherics and second, the determination
of the maximum information on the source itself and external conditions
at detonation time, from the characteristics of the selected pulse.
The 7.1 Castle project offered an opportunity to monitor detonations of
nuclear devices of known composition and characteristics. More specific objectives can be summarized as follows:
1. Determination of pulse character before changes due to propa-
gation become apparent.
,
2. Determination of pulse character as a function of external
parameters such as distance, time of day, and ionospheric conditions.
3. Measurement of field strength.
4. Explanation of the causes of the electromagnetic phenomena
observed.
5. Relation of pulse occurrence to sequence of events during the
detonation.
6. Relation between nuclear-weapon characteristics and pulse
characteristics, both close-in, and, insofar as possible, at distances.
7. Experirentation with prototype surveillance equipment.
8. Measurement of azimithal errors in direction-finding equipment.
9.
Determination of times of pulse reception to within 1 msec in
world time.
BACKGROUND
AFOAT-1 has supported experimental measurements of the pulse emitted at the time of a nuclear detonation during each series of atomic
tests beginning with Buster-Jangle (Autumn, 1951). As a result of these
experiments (References 1,2,3), the following can be stated with some
assurance:
1.
There is an electromagnetic pulse less than 100 psec long
emitted at the time of a nuclear detonation.
2. At a distance of 20 km from the generating source, the field
strength may be a few hundred volts per meter.
3. There is a general relationship between kiloton yield and the
vertical component of the electromagnetic field.
4. The emitted frequency spectrum extends from about 2 ke or
below up to a few megacycles, but the main components are in the region
of about 6 to 50 ke,
i