The objective of the flight was to study stratospheric gravity waves during a long duration balloon mission. The payload, composed by two scientific gondolas suspended at different levels in the flight train, were developed by the Laboratoire de Météorologie Dynamique (LMD) of the Centre National de la Recherche Scientifique (CNRS) while the balloon used for the mission, an Infrared Montgolfier was provided and operated by the Centre National d'Etudes Spatiales (CNES).
As the properties and propagation of gravity waves are strongly influenced by the vertical temperature and horizontal velocity gradients of the medium in which they propagate, to measure these gradients, two gondolas were suspended under the balloon, at 100 m and 300 m respectively. Each one carried a pressure sensor, a temperature sensor, two sonic anemometers (one measuring the vertical relative wind, the other the horizontal relative wind), and two magnetometers used to determine the absolute direction of the measured horizontal wind. The different devices and instruments were mounted on an aluminum frame welded, which also carried a fin that allowed to orient each gondola in the direcion of the wind. The anemometers and the temperature sensor were placed at the end of a horizontal arm pointing upstream of the flow. The support frame measured 2.50 m long and 1.40 m wide high.
In the images at left we can see pictures of the two gondolas that formed the flight train (click to enlarge). Picture up: on the right, the fin (on the non-visible side of which are mounted the two magnetometers). In the middle, at the top of the metal frame, the panels of solar cells. At the bottom of the frame, the two boxes of polystyrene containing respectively the electronics and the pressure sensor (left), and the energy block (right). On the left, carried by the arm, the temperature sensor (suspended at the end of the arm) and the two sonic anemometers (horizontal and vertical). Picture down: on the left, the fin in the middle of which are placed the two magnetometers. In the middle, at the bottom of the metal frame, the two boxes made of polystyrene which respectively contain the energy block (left), and electronics (right). The second box also contained the pressure sensor.
The on-board electronics based on a microprocessor board, managed the instrumental measurements, made calculations of the horizontal wind components relative to a landmark linked to the Earth, calculated the temporal average of the different quantities measured and finally stored and transmitted the processed data using the ARGOS system to NOAA satellites. A circularly polarized antenna, shaped like a Archimedean spiral, was used for data transmission.
The energy supply to each nacelle was provided by a battery of cadmium-nickel recharged by solar cells. It was protected inside a set of polystyrene nesting boxes, separated by mylar sheets, which prevented the temperature from drop below -40°C. The solar cells were gathered in 4 panels 54 x 45 cm, each consisting of 5 rows of six 76 mm diameter cells.
The MONTGOLFIER INFRARED
The balloon used as platform for this mission is the so called Infrared Montgolfier (MIR) developed by the Service d'Aéronomie of the CNRS and CNES in 1977 in an attempt to meet the needs of long-duration flights. The MIR is a hot air balloon "open at the bottom" made of 2 different materials: a top part of aluminized Mylar 12 µm thick making a cavity for absorbing ascendants infrared and block any re-emission toward the sky and the bottom part made of linear polyethylene 15µm thick, an infrared transparent material and tough at cold (-80°C). It only uses helium to gain altitude at takeoff. Their reflective cover provides lift heating the air inside the envelope by the sun during the day or by the infrared radiation coming from the earth during the night. During the day, the MIR flies at an altitude of about 28 km to 32 km while at night it floats between 18 and 22 km depending on the infrared flux radiating from the overflown area and the temperature of the air parcel. It could carry a scientific payload of about 50 kg.
Balloon launched on: 12/11/1982
Launch site: Paardefontein Tracking Station, Pretoria, Southafrica
Balloon launched by: Centre National d'Etudes Spatiales (CNES)
Balloon manufacturer/size/composition: Montgolfier Infrared 40.000 m3
End of flight (L for landing time, W for last contact, otherwise termination time): 2/1/1983
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 53 d
Landing site: Not known. Balloon ceased data transmition over W Angola.
The balloon was launched from the grounds of the Satellite Tracking Station of CNES in Paardefontein, near Pretoria on December 11, 1982. After reaching float altitude it drifted with the easterly winds of the stratospheric summer as we can see in the map above. The mean zonal speed remained mostly unchanged close to 9 meters per second. The balloon movement in latitude was limited to a slow steady drift towards the north, between 25º S at the beginning of the flight and 12º S at the end. On February 2, 1983, one day after completing its first revolution around the globe, the balloon ceased emitting. Apparently it passed the night before above a high cold cloud layer, clearly visible on the images transmitted by the Meteosat satellite, and associated with a very active convective zone. It seems that the IR flux emitted by these cold clouds was not sufficient to maintain the balloon's buoyancy.
This was the first full Earth circunnavigation of an InfraRed Montgolfier balloon.