On the February 22, 2006 launch of their Akari infrared observatory
satellite, JAXA also included a solar sail test and, according to the news
article attached here, they are planning a solar sail-ion propulsion
orbiter/drop probe mission to Jupiter and a Trojan Planetoid.

Experiments to deploy the solar sail

Launch: 21st/Feb/2006 6:28(JST)

The 20m class solar sail film of fan type will be launched as a sub-payload of ASTRO-F (Infrared Imaging Surveyor). JAXA's Solar Sail uses the centrifugal force to deploy and to keep the tension of the film. In this experiment, the deployment speed of the film is gradually changed, and they observe it with two cameras.

Future mission

The solar sail mission to the Jupiter starts if the plan is approved in the committee next month. The explorer is composed of the mother ship and the Jupiter orbiter. There is an idea by which the Jupiter probe which descends to the Jupiter is added, too. There is a rotation drum in the mother ship, and it rotates slowly to keep the tension of the sail of 50m in diameter. Inside 1/3 of the sail (JAXA calls it Solar Powered Sail) is a thin-film solar cell, and the ion engine is driven by the electric power. The weight of the explorer is about 600kg because the installing fuel is a little, and it is launched by using a comparatively small rocket.

In this mission, the following observations are planned.

1. Global Observations from the outside of the ecliptic dust by infrared rays
2. The ecliptic dust distribution observation
3. Magnetosphere observation in polar regions in Jupiter
4. Fly-by observation of Trojan asteroid which exists in Lagrange point (L4) of sun-Jupiter system
5. Gamma rays burst-observation

As for the budget, it is expected to suffice for 100 and several billion yen (one hundred million, several ten million dollars). If this plan is approved in the committee in February, it is launched in the summer of 2010 or 2011, and will arrive at the Jupiter in around 2017. However, there is a mission of two competitions ( VSOP-2 radio astronomy satellite and NeXT X-ray astronomy satellite).

http://uplink.space.com/showflat.php?Cat=&Board=missions&Number=430845&page=1&view=collapsed&sb=5&o=0&fpart=

Images and diagrams here: