The Solar Orbiter crosses the line of the Earth and the Sun as it speeds towards its first historical path close to the Sun

Animation of the ESA/NASA Solar Orbiter passing close to the Sun. Credit: ESA / Medialab

European Space Agency /[{” attribute=””>NASA Solar Orbiter spacecraft is speeding towards its historic first close pass of the Sun. On March 14, the spacecraft will pass the orbit of Mercury, the scorched inner planet of our Solar System, and on March 26 it will reach closest approach to the Sun.

Yesterday, Solar Orbiter crossed directly between the Earth and the Sun, halfway between our planet and its parent star, and this allows for a unique study of space weather and the Sun-Earth connection.

The Sun releases a constant stream of particles into space. This is known as the solar wind. It carries the Sun’s magnetic field into space, where it can interact with planets to create aurorae and disrupt electrical technology. Magnetic activity on the Sun, often taking place above sunspots, can create gusts in the wind enhancing these effects.

This behavior is known as space weather, and scientists can use today’s Earth-Sun line crossing to study it in a unique way. They will combine Solar Orbiter observations with those of other spacecraft operating nearer the Earth, such as the Hinode and IRIS spacecraft in Earth orbit, and SOHO, stationed 1.5 million kilometers away from Earth. This will allow them to join the dots of any space weather event as it crosses the 150 million kilometers between the Sun and the Earth.

The Solar Orbiter’s remote sensing instruments may also be able to determine the origin of any event on the Sun’s surface. One of the main drivers behind the Solar Orbiter’s mission is ‘correlation science’. Even if no major event occurs, there is still a lot of science that can be done in analyzing the evolution of the same solar wind bundle as it travels outward into the solar system.

Due to its location and relative proximity to Earth, the Solar Orbiter has so far been able to maintain almost constant communication, sending large amounts of data. Processing occurs quickly, too. For example, magnetometer data is processed and cleaned within approximately 15 minutes of being recorded. The 15 minutes also includes the three and a half minutes it takes for signals to cross the space between the spacecraft and the ground station.

On February 10, the European Space Agency renamed its upcoming space-weather mission from Lagrange to Isa Viegel. The spacecraft will be launched sometime in the middle of the decade, and it will be a solar observer, constantly monitoring the sun for unpredictable magnetic activity so that Earth’s infrastructure, satellites, residents, and space explorers can be protected from these unexpected events.

The Solar Orbiter is currently located about 75 million km from the Sun. That’s the same distance the spacecraft achieved during its close pass to the sun on June 15, 2020, but nothing compared to how close it is now.

“From this point on, we ‘get into the unknown’ regarding Solar Orbiter’s observations of the Sun,” says Daniel Muller, Solar Orbiter Project Scientist.

On March 26, the Solar Orbiter will be less than a third of the distance from the Sun to Earth, and is designed to survive for relatively long periods. It will spend from March 14 to April 6 inside the orbit of the planet Mercury. Around perihelion, which is the name of the closest approach to the Sun, solar orbit will bring high-resolution telescopes closer than ever to the Sun.

Combined with data and images from the Solar Orbiter’s other instruments, these could reveal more information about the miniature flares dubbed campfires that the mission revealed in its first images.

The Solar Orbiter is a set of ten science instruments that will study the Sun. There are two types: on-site sensing and remote sensing. Instruments on the site measure the conditions surrounding the spacecraft itself. Remote sensors measure what is happening at great distances. The two data sets can be used together to assemble a more complete picture of what is happening in the sun’s corona and solar wind. Credit: ESA-S.Poletti

“What I’m most looking forward to is whether or not all of these dynamic features we see in the Extreme Ultraviolet Imager (polished campfire) can make their way into the solar wind. There are a lot of them!” says Louise Harra, associate principal investigator at EUI based at the Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center (PMOD/WRC), Switzerland.

To do this, the Solar Orbiter will use remote sensing instruments, such as the EUI, to image the Sun, and its on-site instruments to measure the solar wind as it flows through the spacecraft.

The passage of March 26 at perihelion is one of the main events of the expedition. All ten tools will work simultaneously to collect as much data as possible.

Solar Orbiter is a partnership between the European Space Agency and NASA.