June 19, 2018

STRATEOLE-2: the LOAC particle counter joins the Zephyr gondola

In early February, the LOAC particle counter was delivered to the integration and test platform in Guyancourt. Its integration for the flying balloons Strateole-2 project took place without any issue!

Stratospheric cloud - © Holly Troy 2010

The LOAC particle counter is the third and last instrument delivered to the TTL1 installation to be integrated into the Zephyr gondola.

It was developed at the Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E) in Orléans under the responsability of Jean-Baptiste Renard and Pierre Zamora. This instrument weighting a few hundred grammes was designed to be easily used under any type of balloons.

Every month since 2014, LOAC is released by a weather balloon from the CNES base at Aire sur l'Adour in order to carry out a continuous monitoring of the aerosol contents of the atmosphere.

In 2013, LOAC also performed 13 boundary layer pressurised balloon flights and 20 weather balloon flights as part of the ChArMEx campaign to gather data on the transport processes of mineral particles or pollution in the Mediterranean region.

This instrument provides the size distribution for atmospheric particles between 0.2 μm and 100 μm and data on the typology of the particles composing the air mass probed. For this, LOAC studies the scattering of light by particles that are pumped into a small optical chamber from two different angles.

As part of the Strateole-2 project, the LOAC instrument will be used to gather data on the occurrence of convective clouds (cumulonimbus type) entering the lower equatorial stratosphere. These clouds participate very effectively in the transport of water vapour from the lowest layers of the atmosphere to high altitudes.

However, the importance of their contribution to the direct transport of water vapour in the stratosphere is a much-debated subject in the scientific community.

By observing the entire equatorial belt, the LOACs on board these long-duration Strateole-2 flights will study this contribution both over continents and oceans, where convection is usually more vigorous. Finally, the instrument will provide rare data on the aerosol content of the low equatorial stratosphere.


  • Philippe Cocquerez, Project manager of Strateole-2 - philippe.cocquerez at cnes.fr
  • Jean-Baptiste Renard, Head scientist of the LOAC instrument - jean-baptiste.renard at cnrs-orleans.fr
  • Pierre Zamora, Project manager LOAC Strateole-2 - pierre.zamora at cnrs-orleans.fr