The Sun's polar regions remain among the least explored areas in solar science. Space observatories and ground-based telescopes observe the Sun from the plane of the ecliptic—a narrow zone along which Earth and most planets orbit. This limited vantage point restricts our ability to study the Sun’s high-latitude poles.

The magnetic fields in the polar regions play a crucial role in the Sun’s global dynamo process and in shaping the next solar cycle. Data from the Ulysses spacecraft revealed that the fast solar wind originates in vast coronal holes near the poles.

The Sun’s magnetic cycle is a recurring process lasting about 11 years, marked by changes in the number of sunspots and a complete reversal of the magnetic poles. Differential rotation drives magnetic activity, while meridional circulation carries magnetic flux toward the poles.

Decades of helioseismic research have produced conflicting data on the behavior of these flows deep within the convection zone. Some findings suggest flows toward the poles at the base of this zone.

The fast solar wind is a supersonic stream of charged particles that arises in polar coronal holes and fills much of the heliosphere. Scientists are still uncertain about its exact origin—whether it comes from dense jets within coronal holes or from the rarefied regions between them.

Space weather refers to changes in the solar wind and solar eruptions that disturb the space environment. Powerful flares and coronal mass ejections trigger geomagnetic storms on Earth, creating auroras and posing risks to satellites, communication systems, and power grids.

Scientists have long recognized the importance of observing the Sun’s poles. The Ulysses mission, launched in 1990, was the first spacecraft to leave the ecliptic plane and study the solar wind above the poles. Its instruments confirmed key properties of the fast solar wind, but it was unable to capture images.

The European Space Agency’s Solar Orbiter is gradually moving out of the ecliptic plane and will reach latitudes of about 34° in the coming years.

In recent decades, many mission concepts have been proposed, including the Solar Polar Imager (SPI), POLAR Investigation of the Sun (POLARIS), Solar Polar ORbit Telescope (SPORT), the Solaris mission, and the High Inclination Solar Mission (HISM). Some concepts involve solar sails, while others rely on gravitational maneuvers.

The Solar Polar-orbit Observatory (SPO) is scheduled for launch in January 2029. SPO will use a gravity assist from Jupiter to leave the ecliptic plane. After flybys of Earth and an encounter with Jupiter, the spacecraft will enter an orbit with a period of 1.5 years, a perihelion near 1 AU, and an inclination up to 75°. In its extended mission, SPO could reach 80°.

The mission is planned to last 15 years, including a 7-year extended phase. This will allow observations during both the minimum and maximum of solar activity, including the period around 2035, when the next maximum and magnetic pole reversal are expected.

SPO will be equipped with a magneto-helioseismic imager (MHI), extreme ultraviolet telescopes (EUT), an X-ray imager (XIT), a visible coronagraph (VISCOR), and a very large angle coronagraph (VLACOR) to monitor the corona out to 45 solar radii. The in-situ suite includes a magnetometer and particle detectors.

SPO will collaborate with a fleet of solar missions: STEREO, Hinode, Solar Dynamics Observatory (SDO), Interface Region Imaging Spectrograph (IRIS), Advanced Space-based Solar Observatory (ASO-S), Solar Orbiter, Aditya-L1, PUNCH, as well as future missions to the L5 point (ESA’s Vigil and China’s LAVSO).