Via NHK News :
" Fukushima University will check radiation levels high in the atmosphere to get a better grasp of the extent of contamination from the troubled Fukushima Daiichi nuclear power plant.
The university says it will release a large balloon on Friday carrying a weather observation device called a "radiosonde" as well as radiation measurement equipment into the skies above Fukushima City.
It plans to gauge radiation levels and collect other data up to 30 kilometers above ground. Readings will be taken at intervals of 10 meters over a period of 20 days.
The university has so far been measuring radiation closer to the ground. It has checked more than 300 locations in Fukushima Prefecture.
But it deems the current method insufficient to make a correct assessment of the diffusion of radioactive materials."