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SMALL PRESSURIZED BALLOON (SPB)

Historical Information

Following the EOLE experiment which launched with success 480 pressurized balloons at pressure level equal to 200hPa, D. Cadet et H. Ovarlez from the Laboratoire de Météorologie Dynamique (LMD) begun in 1972 to study the use of small pressurized balloons (SPB) to probe the atmospheric boundary layer.

Two preliminary experiments

22 balloons from Rangiroa island in the South Pacific in 1973,
10 balloons from Ascencion island in the South Atlantic in 1974

allowed to put forward difficulties of such flights (Cadet & al. 1975, J. Appl. Met, 14, pp. 1478-1484). These difficulties come from vertical oscillations due to, on the one hand, cooling and radiative heating of envelope, and the other hand, tropical rain effects which can down the balloon close to the sea surface. For balloon with 2m diameter, they estimate the water loading by rain equal to 500g and an additional dynamic pressure around 1000g. The balloon structure coming from the one of EOLE, with the payload under the balloon, didn't allow to stand up to these events since instrumentation is destructed when the balloon hits or gets close to the sea surface (Rangiroa experiment). That is why scientific instrumentation has been located inside the envelope to protect payload from salty water.

This solution has been tested during flights from Ascencion island then used during other experiments such as :

Summer monsoon (45 balloons launched from Seychelles in 1975 ; D. Cadet et H. Ovarlez, Quart. J. R. Met Soc, 1976, 102, pp 805-815),
BALSAMINE (60 balloons from Seychelles et 28 balloons from Diego-Suarez in 1979 ; D. Cadet & al., Bull. Am. Meteor. Soc, 1981, 62, pp. 381-388),
INDOEX (17 balloons launched from Goa in 1999 ; Ethe et al., J. of Geophys. Res., 107D19, 2002, INX2-22-1:19)
BOA (8 balloons launched from Ushuaia in 2000 ; Ethe, PhD thesis, Paris 2001).
VASCO 2005 (5 balloons from Seychelles; http://www.lmd.ens.fr/tromeur/VASCO)
VASCO 2006 (4 balloons from Seychelles; http://www.lmd.ens.fr/tromeur/VASCO)

These pressurized balloons have been fully developed and made at LMD until BOA experiment. Now, balloons are developed by the CNES, balloon envelopes being made by ZODIAC INTERNATIONAL.

Technical Information
Contact : nicolas.verdier@cnes.fr


Superpressure balloons keep a nearly constant volume and therefore fly at a quasi-constant density level, acting as Lagrangian tracers of air parcels and meteorological platforms. Produced by ZODIAC under CNES supervision, balloons are inflated with helium with a nominal 120hPa overpressure at flight level. The envelope, made of three-laminated polyester of 125 micrometers, has a 2.5m diameter spherical shape. With a total mass of approximately 9kg, this vehicle can fly in layers between the surface and approximately 830hPa depending of its ballast. As long as a sufficient overpressure is maintained the volume remains constant, except for slight thermal fluctuations producing low amplitude buoyancy oscillations mostly driven by the diurnal cycle. These balloons proved to be good tracers of horizontal motion close to their equilibrium density level. However, they may react to wind bursts by small amplitude, high frequency, vertical oscillations around this equilibrium level. The most serious problem they encounter is water loading by rain or condensation when the envelope temperature drops under the dew point temperature. This latter case may happen when the balloon enters nearly saturated air or whenever the helium gets cooled by nocturnal radiation.

	Scientific instrumentation on board SPB's consists in air pressure, temperature (Figure at the bottom on the left-hand side) and humidity (Figure at the top on the left hand side) sensors, and a 3D location GPS receiver. Helium temperature and pressure are also recorded. Data are broadcasted, with a mean 15 minutes period, through the ARGOS system. Power is provided by lithium batteries that ensure around a one month lifetime. Batteries, electronics, ARGOS and GPS antenna are all located inside the envelope (Figures on the right-hand side), protected from salty water when the balloon hits or gets close to the sea surface.