During the initial cruise phase, which lasts until November 2021, Solar Orbiter will perform two gravity-assist manoeuvres around Venus and one around Earth to alter the spacecraft’s trajectory, guiding it towards the innermost regions of the Solar System. At the same time, Solar Orbiter will acquire in situ data and characterise and calibrate its remote-sensing instruments. The first close solar pass will take place in 2022 at around a third of Earth’s distance from the Sun.
The spacecraft’s orbit has been chosen to be ‘in resonance’ with Venus, which means that it will return to the planet’s vicinity every few orbits and can again use the planet’s gravity to alter or tilt its orbit. Initially Solar Orbiter will be confined to the same plane as the planets, but each encounter of Venus will increase its orbital inclination. For example, after the 2025 Venus encounter it will make its first solar pass at 17º inclination, increasing to 33º during a proposed mission extension phase, bringing even more of the polar regions into direct view.