Planetary plasma and atmospheres explored by space missions in Japan: Hisaki, Akatsuki, and beyond

Planetary plasma and atmospheres have been challenged by space missions of Japanese science community from 1990s, with ISAS and JAXA. The first trial, a Martian orbiter Nozomi, was launched in July 1998. At the departure from Earth in Dec. 1998, she met an engine trouble but we struggled and found a narrow and long path connecting to the Dec 2003 arrival, which is the simultaneous arrival with ESA Mars Express. Unfortunately, we had an additional power trouble in Apr. 2002 associated with a solar flare event, and we gave up the trial at the gate of Mars in Dec. 2003. In parallel to the Kaguya Lunar orbiter in 2007-2009, a next trial to planets, the Akatsuki orbiter to Venus, was prepared. She departed from Earth in May 2010. However, she got an engine trouble at the arrival to Venus in Dec. 2010, and we again endured another long path, but this road was at last ended by a success of the orbit entry in Dec. 2015. We also created the UV/EUV space telescope, Hisaki, using the sensor and optics technologies extracted from Nozomi. It is going well after the launch in 2013 and actively looking planetary thin atmospheres collaborating with other space missions. This paper summarizes the Hisaki and Akatsuki missions which are now on orbit, with the next missions, Arase (ERG), BepiColombo, JUICE, and beyond.