During IOP 12 several location have been chosen to launch radiosondes at the same time. Our students helped at launching radiosondes at the TARA site. Radiosondes are used to record profiles of the atmospheric state (temperature, pressure, humidity, wind) at high spatial resolution. The dedicated probe that we can see on the right picture is attached to a balloon filled with Helium which bring the probe up to 12-15 km height. At such height, the balloon usually increases so much in volume due to the difference of pressure with the surrounding that it explodes. Data recorded are transfered via radio frequence to the surface where they are processed and displayed near real time. For hymex, data are recorded and kept in both ascent and descent of the probe within the atmosphere.