The Solar Polar-orbit Observatory (SPO) mission, set to launch in January 2029, will provide the first direct views of the Sun's polar regions. These areas, long hidden from Earth's orbital perspective, are key to understanding the solar magnetic cycle, fast solar wind, and space weather. The mission aims to address fundamental questions in solar physics through advanced imaging and in-situ measurements.
The Sun's polar regions have remained largely unexplored due to observations being confined to the ecliptic plane, where Earth orbits. These high-latitude areas are essential, as their magnetic fields drive the Sun's 11-year magnetic cycle, which involves sunspot fluctuations and polar field reversals. They also originate the fast solar wind from coronal holes, influencing the heliosphere and space weather events like flares and coronal mass ejections that can disrupt Earth's satellites and power grids.
Past efforts include the Ulysses spacecraft, launched in 1990, which sampled polar solar wind but lacked imaging. The European Space Agency's Solar Orbiter is approaching 34° latitudes but falls short of true polar views. Proposed concepts like the Solar Polar Imager and POLAR Investigation of the Sun have not yet launched.
SPO will use a Jupiter gravity assist after Earth flybys to achieve an orbit with 75° inclination, extending to 80° in its seven-year extended phase. Over its 15-year lifetime, it will observe both solar minimum and maximum, including the 2035 polar reversal. Instruments include the Magnetic and Helioseismic Imager for surface fields, Extreme Ultraviolet and X-ray telescopes for atmospheric dynamics, coronagraphs to track the corona out to 45 solar radii, and in-situ sensors for solar wind and magnetic fields.
The mission will complement existing observatories such as STEREO, Hinode, Solar Dynamics Observatory, Solar Orbiter, and upcoming L5 missions, enabling near-global coverage of the Sun. By clarifying the solar dynamo, fast solar wind acceleration, and space weather propagation, SPO could improve cycle predictions and protect technologies on Earth.