In the depths of space, where the constant stream of particles from the Sun meets our planet's magnetic shield, a new era of scientific research is being born. At the heart of this revolution is the Smile mission (Solar wind Magnetosphere Ionosphere Link Explorer), an ambitious joint project of the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS). The goal of this mission is unique: to capture for the first time the global interaction between the solar wind and Earth's magnetosphere in real-time, making previously invisible processes visible. With a launch planned for 2026, Smile promises to uncover the secrets of space weather that directly affect our technological world.

This mission represents a milestone in space research cooperation, combining the expertise and resources of Europe and China in an endeavor that will redefine our understanding of the dynamic processes that shape the space environment around Earth. Smile will provide us with the first movies and images of the interaction between the solar wind and Earth's magnetic field, allowing scientists to track the entire chain of events, from the arrival of the solar wind to its impact on our planet.

Mission's Scientific Objectives: Understanding the Cosmic Battle

Earth is continuously bombarded by the solar wind, a stream of charged particles ejected by the Sun at speeds of hundreds of kilometers per second. Fortunately, our planet has a powerful defense: the magnetosphere, an invisible magnetic bubble that repels most of these particles. However, this interaction is not simple; it is dynamic and sometimes dramatic, and we feel its consequences as space weather. The main scientific goal of the Smile mission is to investigate this fundamental connection. The mission will focus on studying how energy and particles from the solar wind are transferred into Earth's magnetosphere. Special emphasis will be placed on a process known as magnetic reconnection, a key mechanism that allows the solar wind to "breach" our magnetic shield on the dayside of Earth. Smile will simultaneously observe the global effects of this interaction, such as geomagnetic storms and substorms, which can damage satellites, disrupt communication and navigation systems, and even cause power outages on Earth. By observing the entire process, from the initial collision to the final consequences in the form of the aurora, Smile will provide a complete picture that has been missing until now.

Innovative Instruments for a New View of Space

To achieve its ambitious goals, the Smile spacecraft, weighing about 2.3 tons, is equipped with four state-of-the-art scientific instruments that will work in concert. Two of them are imaging instruments that will provide a global view, while the other two perform measurements at the spacecraft's location (in-situ).

• Soft X-ray Imager (SXI): This is the "star" of the mission. SXI is a wide-field-of-view telescope that uses innovative "lobster-eye" optics to detect soft X-rays. These rays are produced when highly charged ions from the solar wind collide with neutral atoms in the outermost parts of Earth's atmosphere, the exosphere. For the first time, SXI will be able to image the boundaries of Earth's magnetosphere—the bow shock and the magnetopause—allowing scientists to see how these boundaries move and change under the influence of the solar wind.


• Ultraviolet Imager (UVI): This instrument will provide the longest continuous observation of the northern aurora to date. UVI will capture the ultraviolet radiation emitted by particles as they enter Earth's upper atmosphere. Since SXI and UVI will observe simultaneously, scientists will be able to directly link events at the edge of the magnetosphere with the intensity and location of the aurora, providing a crucial link in understanding the cause-and-effect chain of space weather.


• Light Ion Analyzer (LIA): This instrument will directly measure the properties of solar wind particles and those within the magnetosphere. It consists of two sensors placed on opposite sides of the spacecraft to measure the density, velocity, and temperature of ions (primarily protons and alpha particles) passing by the satellite. This data will provide essential context for the images captured by SXI and UVI.


• Magnetometer (MAG): Located on a 3-meter-long boom to avoid magnetic interference from the spacecraft itself, the magnetometer will precisely measure the strength and direction of the magnetic field of the solar wind and Earth's magnetosphere. This data is essential for understanding how magnetic fields intertwine and reconnect, driving energetic processes in space.

A Partnership That Pushes Boundaries

Smile is not just a technologically advanced mission, but also a significant geopolitical and scientific undertaking. It is the first mission in which the European Space Agency and the Chinese Academy of Sciences have collaborated from the very beginning—from a joint call for proposals in 2015, through joint selection, design, development, to the future launch and operations. This deep collaboration demonstrates how scientific goals can be achieved when resources and knowledge are pooled across continents. In this division of labor, ESA is responsible for the Payload Module that houses the instruments, the launch itself, one of the scientific instruments (SXI), and part of the science operations. On the other hand, CAS provides the spacecraft platform, three scientific instruments (UVI, LIA, MAG), as well as the overall mission and science operations after launch. This synergy has enabled the creation of a mission that would have been significantly more difficult for either agency to realize alone.

Final Preparations Before Launch

To ensure the spacecraft is ready for the harsh conditions of space, Smile recently underwent an intensive four-month testing phase at ESA's technical heart, the ESTEC facility in the Netherlands. Engineers from Europe and China, including experts from companies like Airbus and European Test Services, worked together to subject Smile to a series of rigorous checks. The tests simulated all the challenges the spacecraft will face: from the powerful vibrations and noise during a rocket launch, to the extreme vacuum of space, to the temperature shocks caused by alternating between direct sunlight and darkness. Key team members, such as David Agnolon, Smile's Project Manager from ESA, and Li Jing, Project Manager from CAS, along with their teams of engineers like Chris Runciman, Laura Malene Lottes, Benjamin Vanoutryve, He Tau, and Zhu Xiaofei, oversaw these crucial tests. The successful completion of this phase represents a huge step forward and confirms that Smile is robust and ready for its journey.

Journey on the Wings of a Vega-C Rocket

When finally ready, the Smile mission will begin its journey to a unique, highly elliptical orbit from Europe's Spaceport in Kourou, French Guiana. The European rocket Vega-C, a powerful and versatile launcher designed to carry medium-sized payloads, has been selected for the launch. Vega-C, standing about 35 meters tall, is capable of delivering a payload of over two tons to a polar orbit, making it ideal for the needs of the Smile mission. The mission's trajectory has been carefully designed. Smile will be placed in a highly inclined and elongated orbit that will take it to an altitude of nearly 120,000 kilometers, almost a third of the distance to the Moon. From this distant vantage point above the North Pole, the spacecraft will spend about 80% of its time, providing it with a perfect view for capturing global images of the magnetosphere. This orbit also minimizes the time spent in the dangerous Van Allen radiation belts, protecting the sensitive instruments and ensuring the mission's longevity, which is nominally planned for three years. You can follow all the latest news and progress of the mission on the official website esa.int/smile.

Source: European Space Agency