Solar Orbiter crosses the Earth-Sun line as it heads for the Sun

on 14 March 2022

The ESA/NASA Solar Orbiter spacecraft is speeding towards its historic first close pass of the Sun. Today, 14 March, the spacecraft passes the orbit of Mercury and on 26 March it will reach closest approach to the Sun.

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 behaviour 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 kilometres away from Earth. This will allow them to join the dots of any space weather event as it crosses the 150 million kilometres between the Sun and the Earth.

Solar Orbiter’s remote sensing instruments may also be able to pinpoint the origin of any event on the solar surface. Such ‘linkage science’ is one of the main drivers behind the Solar Orbiter mission.

Because of its position and relative proximity to Earth, Solar Orbiter has so far been able to stay in almost continual contact, beaming back large quantities of data. The processing is happening quickly too. For example, the magnetometer data is processed and cleaned within roughly 15 minutes of it being recorded. The 15 minutes even includes the three and a half minutes that it takes for the signals to cross space between the spacecraft and the ground station.

On 26 March, Solar Orbiter will be less than one-third of the distance from the Sun to the Earth, and it is designed to survive this close for relatively extended periods of time. It will spend from 14 March to 6 April inside the orbit of Mercury. Around perihelion, the name for closest approach to the Sun, Solar Orbiter will bring high resolution telescopes closer than ever before to the Sun.

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

More details here.

Image credit: ESA / Medialab