Purpose of the flight and payload description

The objective of this series of flights was to measure the directional distribution of cosmic rays at atmospheric depths of 15 to 25 g/cm2. The experiments were conducted from the U.S.S. Norton Sound at geomagnetic latitudes of 0°, 20°, 30° and 40° on a cruise from Port Hueneme, California, to Jarvis Island and return, between July and August 1949.

In the image at left we can see the basic measuring instrument used in the campaign (click to enlarge). It was a three fold Geiger counter coincidence telescope, composed by Geiger counters of 1 inch diameter, installed on three 10 x 10 inches trays and spaced 50 inches between extremes. This construction represented a considerable improvement in counting rate and angular resolution over the geometry previously employed by the same scientific group.

The telescope, complete with high and low voltage dry batteries for 15 hours operation, was an independent unit and was hung by its shaft in a vertical frame with a motor and gear drive arranged to control the zenith position during flight according to a prescribed schedule. During flight the entire gondola was rotated with a period of about 18 minutes by a large gear and motor about a ball-bearing vertical shaft. This shaft was effectively anchored to the balloon by a non-twisting, double suspension about 10 feet below the balloon load ring. The complete gondola ready to fly weighed from 105 to 115 pounds.

The pressure (altitude) was measured during the rising portion of the flight by a baroswitch aneroid element supplemented by a non-spillable mercury manometer, while temperatures were measured by a thermistor. This information along with the counting rate of the instrument at altitude was telemetered back to the ship using an audio F.M. sub-carrier system of transmission. Radar tracking facilities available on the "Norton Sound" provided time-altitude curves and geographic course charts of the balloons within a 75 mile radius of the ship.

None of the gondolas were recovered, so that post-flight checks of the instrument was not possible.

Details of the balloon flight

Balloon launched on: 7/12/1949
Launch site: USS Norton Sound (AVM-1)  
Balloon launched by: Office of Naval Research (ONR)
Balloon manufacturer/size/composition: Zero Pressure Balloon  
End of flight (L for landing time, W for last contact, otherwise termination time): 7/??/1949

External references

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