The objective of the flight was to investigate the Earth-ionosphere wave-guide, using a series of receivers onboard a balloon in the stratosphere that received the electromagnetic field signals transmitted by the 166 kHZ antenna of the Sainte-Assise complex, a very low frequency (VLF) radio transmitter and military installation located near Paris. The experiment was carried out by the Groupe de Recherches Ionospheriques of the Centre National de la Recherche Scientifique (CNRS) from France. The observations were intended to made new contributions to the study of VLF propagation providing information about the influence of both the ground and the ionosphere.
The various elements of the experimental device are shown in the figure at left (click to enlarge). The method of measurement of the electromagnetic field was similar to that employed on the FR-1 satellite: the received signal at 16,800 Hz was mixed with that from a reference oscillator at 16,810 Hz and the beat frequency of 10 Hz was passed through a low pass filter system, such that relative phases were conserved. Solar sensors and a triaxial magnetometer provided the restitution of attitude. The spin axis was vertical and the horizontal antennas aboard the balloon rotated around this axis and gave successively the same signal. Furthermore, the 10 Hz beats amplitudes and phases were modulated by the balloon's rotation and these modulations were strongly interrelated, depending on the horizontal polarization of the electric or magnetic field.
The observations were complemented on the ground with a series of similar sensors to the one located in the balloon which were setup at the Aire Sur L'Adour site.
Balloon launched on: 11/12/1969 at 11:00 utc
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): 11/12/1969 at 13:00 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 2 h
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