Results of RAIJIN2012, the intensive observation program to relax the triggered lightning launch commit criteria

Space transportation is one of the core operation in a wide range of space programs of Japan Aerospace Exploration Agency (JAXA). In those operations, one of the most important responsibilities is to assure safety of flight under any weather conditions. Among various hazardous atmospheric phenomena, specific rules and regulations are required especially for a triggered lightning since it is very capable of exerting a catastrophic influence on launch vehicle ascending into space. In order to avoid triggered lightning strikes to space vehicles, "Thick Cloud Rule" is applied to the weather launch commit criteria, which severely restricts a launch vehicle to lift off. However, since there have been no failure caused by triggered lightning so far, this rule is thought to be highly conservative and may issue an false alarm which may even leads to economic loss and other costs. To promote optimal operation, achieving both enhanced safety and increased launch opportunities, research plans are schemed and an intensive observation project called RAIJIN was conducted in Feb. 2012. This paper shows an overview of the RAIJIN 2012 project and specific results to be applied to relax the triggered lightning launch commit criteria focusing on observations of X-band dual polarization Doppler radar, video sonde, and airborne field mill.