Purpose of the flight and payload description

At the end of the 1980's decade the Centre des Faibles Radioactivités a French research centre managed by the Centre national de la recherche scientifique (CNRS) and the Commissariat à l'Energie Atomique (CEA) established a balloon-borne sampling program to study the exchanges between the surface of the continents and the upper atmosphere using as a tracer Krypton-85, a rare radioactive gas injected in the atmosphere during the reprocessing of bars of nuclear fuel. Chemically inert, this gas has a radioactive half-life of 10.76 years which gives it enough life time to reach the upper layers of the stratosphere.

In the image at left we can see the payload being readied in the laboratory for a flight (click to enlarge).

Once the balloon reached the stratosphere the instrument initiated a sampling sequence of the sourrounding air. The sampled air was first compressed by a mechanical booster pump, and then by a one stage rotary pump. Oil and water vapours were removed in a liquid nitrogen cooled trap, and the air was blown through one trap filled with activated charcoal, and maintained at 120º K by liquid nitrogen. The sampling device comprised five such independent traps selected by valves operated by remote control. A total of four samples were collected during the flight while a fifth trap was maintained closed during the flight as a blank, in order to detect the presence of any contamination.

After recovering the sampler, the air -already enriched in rare gases- was desorbed by heating and the krypton of the air was again trapped in cold charcoal and then separated and measured by gas chromatography. This krypton was subsequently introduced into a beta counter whose volume was completed by a classical Argon-Methane mixture, in order to measure the Kr-85 activity. Almost six flights were made for the program between 1986 and 1990.

Details of the balloon flight

Balloon launched on: 10/1/1987
Launch site: Centre de Lancement de Ballons CLBA, Aire Sur L'Adour, Landes, France  
Balloon launched by: Centre National d'Etudes Spatiales (CNES)
Balloon manufacturer/size/composition: Zero Pressure Balloon  
End of flight (L for landing time, W for last contact, otherwise termination time): 10/1/1987

External references

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