DESCARTES is the acronym of Détermination Et Séparation par Chromatographie lors de l'Analyse des Résultats des Traceurs Échantillonés dans la Stratosphère (Determination and separation by chromatography in the analysis of tracer results sampled in the Stratosphere). It is an instrument developed by the University of Cambridge for the measurement of long-lived trace gases (CFC-11, CFC-113, CCl4 and CH3CCl3) in the stratosphere. The low weight of less than 20 kg and no need of telemetry make the instrument suitable for being launched on small balloons or fly as piggyback on larger balloons.
The working principle is to let an amount of air pass through 16 sample tubes containing a Carboxen adsorbent. A valve allows only one tube at a time to be exposed to the air flow. Trace gases will then be trapped inside the sample tubes while the rest passes through. An on-board computer controls the sampling sequence, and also measures the flow of air, the pressure and temperature, the level of the batteries, and the state and position of the valve.
After the flight, the data is downloaded from the computer, the sample sizes are determined and the sample box is connected to a gas chromatograph for quantification.
Balloon launched on: 8/14/2000 at 9:12 utc
Launch site: European Space Range, Kiruna, Sweden
Balloon launched by:
Balloon manufacturer/size/composition: Zero Pressure Balloon
End of flight (L for landing time, W for last contact, otherwise termination time): 8/14/2000 at 11:32 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 2 h 30 m
Landing site: Near Kangos, Sweden
During this third and last flight of the SAMMOA campaign in Esrange, two units of DESCARTES were used one belonging to the University of Cambridge and the other from the Swedish Institute of Space Physics. One of the instruments was run in a normal mode to take samples from 350 to 10 hPa and the other was used to improve height resolution in the upper troposphere and lower stratosphere as much as possible. Both instruments were analysed in Kiruna and the overlapping samples shows the same profile within the estimated error limit.
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