Purpose of the flight and payload description
This was a technological flight of BOCCAD (Balloon OCCultation for Aerosol Detection) an instrument developed in 1994 by the Laboratoire d'Optique Atmosphérique (LOA), Université des Sciences et Technologies de Lille in France. The aim of the instrument was to observe solar occultation through the atmosphere. It was planned to provide useful information for other LOA experiment known as RADIBAL (RADIometer BALloon), and to provide a direct comparison with satellite measurements SAGE II and a POAM II.
At left we can see an schematic description of the instrument (click to enlarge). The objective formed the Sun's image on a CCD matrix of 244 by 550 pixels. The vertical and horizontal FOV of the instrument were 10° and 7.5° respectively. A filter wheel, located between the objective and the detector, allowed multispectral measurements to be performed. Three interference filters centered at 850, 780 and 443 nm were used for aerosol studies, and a fourth channel at 600 nm was dedicated to ozone detection. BOCCAD was installed on the same gondola as BALLAD and also operated at the balloon ceiling level. The gondola stoped rotating after the BALLAD measurements and the instrument pointed 2° below the balloon horizon so that the large FOV allowed observation of the whole occultation event. The measurements started when the solar elevation reached ca. 2° and the Sun's image could be obtained almost outside the atmosphere to provide a reference image in each channel. Typically about 300 images were formed successively in each channel during a sunset at high latitudes.
Details of the balloon flight
Balloon launched on: 11/30/1994 at 13:44 utc
Launch site: Virgen del Camino Airport, León, Spain
Balloon launched by: Centre National d'Etudes Spatiales (CNES)
Balloon manufacturer/size/composition: Zero Pressure Balloon model 100sf Zodiac - 100.000 m3
Balloon serial number: 100 SF Nº 223
End of flight (L for landing time, W for last contact, otherwise termination time): 11/30/1994 at ~ 17:45
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 4 h 2 m
Payload weight: 520 kgs
Gondola weight: 251 kgs