Recent progress of Scientific Balloon Activities in Japan Hideyuki Fuke 1, * for JAXA Scientific Ballooning Research and Operation Group 1

Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan *

E-mail: [email protected]

JAXA/ISAS has conducted scientific ballooning in Japan for 50 years since 1966. Since 2008, annual domestic balloon campaigns have been carried out at Taiki Aerospace Research Field (TARF), Hokkaido. A dedicated launch equipment “Sliding launcher” enables us to inflate the balloon indoors safely. The so-called “boomerang flight operation” is adopted to maximize the balloon flight duration while making sure of quick recovery both of payload and balloon in coastal waters. Fruitful results have been achieved by many projects from various academic fields such as atmospheric science, astrobiology, space engineering, as well as cosmicray physics and astronomy. Nowadays, due to more unfriendly weather condition, tighter safety requirements, and the lack of resources, it becomes difficult to make our domestic scientific ballooning more active in terms of balloon size, payload weight, and flight duration. In 2015, JAXA/ISAS has carried out a balloon campaign at Alice Springs, Australia, as a precursor of future sustainable overseas activities. The balloon campaign at Alice Springs is complimentary to the domestic campaign at TARF in order to realize longer flight duration, ground recovery, and observations in the Southern Hemisphere. In addition to the balloon flights provided by JAXA, Japanese scientists consider to obtain valuable flight opportunities conducted by foreign space agencies in order to carry out the cutting-edge space sciences. In order to explore the mesosphere much easier, JAXA/ISAS has developed ultra-thin-film balloon step by step. In 2013, we fabricated an 80,000 m3-volume balloon with 2.8-micron polyethylene film. This balloon hanging a 3 kg payload reached an altitude of 53.7 km, the world record of the highest altitude of unmanned balloon. Though this type of ultra-thin-film balloons already have been used for atmospheric observations, we will develop a reinforced type which can lift a 10 kg science payload above 50 km altitude to enlarge scientific capabilities of ultrathin-film balloons. At the workshop we will report on the details of the current status and future prospects of the Japanese scientific ballooning.