Purpose of the flight and payload description

The payload was composed of a grille spectrometer associated with a telescope and a Sun pointer. The goal of the flight was to perform spectroscopic measurements of HCl in a portion of the fundamental band in the 3 microns wavelength region.

The spectrometer used a Littrow mounting with an off-axis parabolic mirror whose focal length wass 60 cm. The grille was deposited on an 18 x 18 mm calcium fluoride window. The signal was chopped at 360 Hz by vibrating the collimating mirror at 180 Hz, which was the resonance frequency of the mechanical mounting included in the servo system stabilizing the vibration amplitude. The spectral calibrations were performed by means of H2O and CO2 absorption lines and by the simultaneous recording of the spectra and of position grating marks. To maintain the instrumental performance during flight the optical path inside the spectrometer is servo controlled to balance the mechanical deformations due to temperature and attitude alterations. Two auxiliary grilles located alongside of the main grille were used for this purpose. The first was illuminated by a filament lamp, with ray paths close to the path of the solar radiation to be measured. The light flux was received on a gold doped germanium photodiode after reflection on the second grille. The detector signals were preamplified and telemetered to the ground through three channels having different sensitivities.

A 4.2 m focal length modified Cassegrain telescope of 32 cm diameter was used to image the Sun on the grille. The Sun pointing system controls the attitude of the spectrometer telescope assembly. The gondola on which the payload was mounted counted with an azimuth control unit and with a servocontrolled plane mirror for elevation and fine azimuth sun tracking.

Details of the balloon flight

Balloon launched on: 10/2/1975
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 model 100z Zodiac - 100.000 m3
Payload weight: 217 kg

External references

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