Purpose of the flight and payload description
The objective of the flight was to obtain atmospheric air samples during a stratospheric balloon in the stratosphere. The instrument -a whole air sampler- was developed in the decade of 1960 by the National Center for Atmospheric Research in Boulder, Colorado. It flew in several balloon missions between 1965 and 1973.
The whole air sampling technique involves taking an air sample into a suitable container (ideally without fractionation of its constituents). This can be accomplished in several ways, the simplest being to expose a previously evacuated container to ambient air, and after pressure equilibration, to close it. In this way a so-called "grab sample" is obtained for which the sample pressure is that of ambient air at sampling altitude. Because of its simplicity grab sampling can be carried out on any vehicle, aircraft, balloon, or rocket and the method has been used widely.
To obtain the vertical profiles a grab sampler was carried by balloon to an altitude of 30 km and opened at different altitudes during descent. The balloon sampling train is shown in the figure at left. The gas sampling device, consisted of eight evacuated bottles which could be connected in turn to a sampling manifold by a rotary valve. Prior to opening the bottles to the atmosphere, the manifold was flushed about 20 times with ambient air by a small pump, and the residual pressure (if any) in the bottles was measured by thermocouple gauges. The bottles were constructed by welding the mouths of two 2 liter stainless steel beakers together. An inlet to this bottle was provided by a 0.63 cm outer diameter spigot and a small instrument type valve was used to isolate the bottles from the sampler. The material used was stainless steel.
The payload was suspended about 150 m below the balloon to prevent contamination with the helium vented by the balloon. To reduce contamination from the gondola itself, the sample intake was located about 6 m below and the inlet line was flushed about 20 times prior to sampling using a liquid Nitrogen cooled adsorption pump. As an additional precaution sampling was done during descent only. This virtually eliminated any external contamination.
Details of the balloon flight
Balloon launched on: 7/9/1967 at 7:10 cdt
Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US
Balloon launched by: National Center for Atmospheric Research (NCAR)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen 1.600.000 cuft (1.0 MIL. Stratofilm)
Balloon serial number: SF-162.3-100 NS-01 Serial Nº 96
Flight identification number: 325P
End of flight (L for landing time, W for last contact, otherwise termination time): 7/9/1967
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): F 1 h 50 m
Landing site: San Angelo, Texas, US
Payload weight: 697 kgs
Balloon ascended normally to a float altitude of 104.500 ft. Two air samples were taken during float. The balloon was valved to 85.000 feet where an attempt was made to collect the 3rd air sample. The gondola did not respond to the scientific commands and was valved down to 70,000 feet where the flight was terminated.