SMILE: European Space Weather Mission Launches

A new mission just launched to probe the interactions of the solar wind with our local space-weather environment, called the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE).

The mission, a partnership between the European Space Agency (ESA) and China’s Academy of Sciences (CAS), lifted off on a four-stage Vega-C rocket from the Guiana Space Center at 11:52 p.m. EDT on May 19th (3:52 UT May 19th). Controllers report that the solar panels have successfully deployed, and the spacecraft is in good health. ESA is tracking the mission via its New Norcia station in Australia, which is part of ESA’s worldwide network of relays.

SMILE is equipped with four instruments to make in situ measurements of the solar wind, the stream of charged particles and magnetic fields that are continuously flowing off the Sun. The following instruments are on board:

• Soft X-ray imager (SXI), a wide-field “lobster eye”’” instrument
• Ultraviolet Imager (UVI)
• Light Ion Analyzer (LIA)
• Magnetometer (MAG)

The SXI was designed and built by the University of Leicester in the United Kingdom; CAS built and operates the other three.

To accomplish its mission, SMILE is headed toward a high-inclination, elliptical Earth orbit that, every 40 hours, will take it out to an apogee about 121,000 kilometers (75,000 miles) from Earth. That’s more than a quarter of the way to the Moon.

“[SMILE] builds on ground-breaking scientific and technological heritage from previous missions, including Cluster and XMM-Newton,” says Carole Mundell (ESA Director of Science) says in a recent press release, “taking tried-and-tested technologies and applying them in a new way to reveal Earth’s magnetic environment like never before.”

Understanding how Earth’s magnetic field interacts with the space environment it orbits through is key to space weather forecasting. As we come off the peak of Solar Cycle 25, the Sun is still active, and flares and ejections of particles still have the potential to disturb satellites. Though there are several space-weather missions in Earth orbit, the boundaries of Earth’s magnetosphere — where Earth’s magnetic field meets that of the solar wind — are still poorly understood.

To that end, SMILE will collect data on Earth’s daytime magnetosphere as well as the magnetopause, the interface between Earth’s magnetosphere and the solar wind. Those data will give scientists a good look at the polar cusp regions, where the solar wind dips down to the upper ionosphere. The mission will also watch the evolution of the auroral oval during geomagnetic storm events. All of these observations will give us a unique outside-in view of Earth’s magnetic environment, and the first X-ray views of Earth’s magnetic shield.

SMILE could address a lingering question: How do geomagnetic events trigger substorms in Earth’s magnetic field? Substorms pump charged particles into Earth’s upper atmosphere at high latitudes, but the exact period and timing for how this occurs has remained unclear. SMILE will watch substorms develop in real time and measure their strength.

SMILE has a three-year nominal mission and will complement the data coming from ESA’s Swarm mission, a trio of spacecraft launched in 2013 and still active. SMILE also bridges the gap to ESA’s planned flagship space-weather mission, Vigil, which will launch in 2031 and head to the L₅ Lagrange point that trails Earth in its orbit.

In a very real sense, we live within the atmosphere of a sometimes tempestuous star. SMILE will help us to better understand the whims of space weather, including its role and impact on Earth’s geomagnetic environment.