Solar Polar Orbiter
The solar polar orbit is a mission concept to observe the sun's poles. The spacecraft spirals in towards the sun to about half Earth's distance (0.48 AU), then inclines the orbit until it passes over both poles. From this vantage point, a spacecraft can image the polar regions of the sun, and monitor the solar wind from these regions, to better understand how the sun works. This is a very energy intensive mission, which solar sails would be well suited for, because of the abundant sunlight. Ulysses is the only current mission which observes the sun's poles.