China-Europe SMILE mission launch to enhance space weather forecasting

The successful launch of the Solar wind Magnetosphere Ionosphere Link Explorer satellite on Tuesday, aimed at studying how streams of charged particles from the sun interact with Earth's magnetic field, marks a milestone in China-Europe space cooperation.

The satellite was launched by a Vega-C rocket from Europe's spaceport in Kourou, French Guiana. Following liftoff, the satellite entered its planned orbit, with solar arrays deployed and all systems operating normally. The mission is a collaboration between the Chinese Academy of Sciences and the European Space Agency.

"Earth is surrounded by an invisible magnetic field, the magnetosphere, which functions like a protective umbrella and deflects most of the solar wind — high-speed streams of charged particles from the sun. Without this protective shield, life on Earth would not be able to survive," said Wang Chi, a CAS academician and the Chinese principal investigator of the SMILE satellite.

Wang, who is also the director of the CAS National Space Science Center, said when some charged particles break through the magnetic shield and enter near-Earth space, they can disturb the space environment, threaten satellites in orbit, interfere with communication and navigation systems, and even trigger large-scale power outages.

Previous studies of Earth's magnetic environment have mainly relied on isolated observations from individual satellites, making it difficult for scientists to obtain a complete picture of how the system works.

With SMILE now in orbit, scientists will for the first time conduct panoramic imaging of Earth's magnetosphere, allowing them to observe its overall structure. Shaped by the pressure of the solar wind, the boundary of the magnetosphere resembles a smile, also the mission's name. The mission will also help scientists better understand how the solar wind interacts with Earth's magnetic field and improve space weather forecasting capabilities.

To achieve these goals, SMILE carries four advanced scientific instruments. The core payload is the Soft X-ray Imager, which detects X-rays generated when particles from the solar wind interact with particles in Earth's upper atmosphere. This allows scientists to observe the previously invisible boundary of the magnetosphere for the first time.

The three other instruments include: an Ultraviolet Aurora Imager for photographing auroras near Earth's polar regions, a Light Ion Analyzer for measuring charged particles, and a Magnetometer for monitoring changes in Earth's magnetic field. Together, these instruments will provide both large-scale images and direct measurements, providing scientists with new tools to study geomagnetic storms and other space weather events.

Beyond its scientific value, Dai Lei, chief designer of SMILE's science application system and a professor at the National Space Science Center, said the mission demonstrates an equal and mutually beneficial model of cooperation between China and Europe.

"Building upon the legacy of the Double Star Program — a China-led space cooperation project with ESA proposed in 2003 — SMILE has established a new model for international space collaboration. This is the first bottom-up, mission-level, full life-cycle partnership between CAS and ESA," Dai said.

CAS took primary responsibility for the satellite platform, mission operation and control, and the science application system, while ESA provided the payload module, launch vehicle, launch site, and ground tracking and emergency support.

The University of Leicester in the United Kingdom led the development of the Soft X-ray Imager, while CAS led the development of the other three instruments with support from European partners in key components and calibration work.

Over the past decade, the mission established an integrated engineering system involving six major subsystems. Scientists and engineers from both sides jointly addressed technical challenges such as cross-regional design coordination, system compatibility and joint testing, helping ensure the mission's timely and smooth implementation.

SMILE will spend about 42 days maneuvering into its final science orbit. It will then undergo a two-month in-orbit testing phase before beginning its planned three-year observation mission.

During its operational lifespan, scientists from China and Europe will jointly process and analyze the data collected by the satellite. All scientific data will be openly shared with the global research community to encourage wider international participation and research.

The long-term data gathered by SMILE is expected to deepen understanding of interactions between the solar wind and Earth's magnetic field, while also helping improve the accuracy of space weather forecasts and the safety of near-Earth space activities.

Looking beyond SMILE, Wang outlined broader plans for China-Europe cooperation in space science. He said the China-Europe space exploration program, which includes the SMILE mission, will launch a series of satellites during the 15th Five-Year Plan period (2026-30).

These include the Hongmeng Project to study the universe's earliest period after the Big Bang, the Earth 2.0 mission to search for planets similar to Earth, and the enhanced X-ray Timing and Polarimetry space observatory (eXTP), which will explore extreme cosmic conditions such as black holes and neutron stars, Wang said.