Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a spacecraft mission of the European Space Agency and the Chinese Academy of Sciences launched on 19 May 2026 from the Guiana Space Centre in French Guiana. SMILE will image for the first time the magnetosphere of the Earth in soft X-rays and UV during up to 40 hours per orbit, improving the understanding of the dynamic interaction between the solar wind and Earth's magnetosphere. The mission is estimated to last for three years. The prime science questions of the SMILE mission involve the fundamental modes of dayside solar wind-magnetosphere interaction, the processes defining the substorm cycle, and how coronal mass ejection-driven storms develop and relate to substorms.
Objectives The mission will observe the solar wind interaction with the magnetosphere with its X-ray and ultraviolet cameras (SXI and UVI), gathering simultaneous images and videos of the dayside magnetopause (where Earth's magnetosphere meets the solar wind), the polar cusps (a region in each hemisphere where particles from the solar wind have direct access to Earth's ionosphere), and the auroral oval (the region around each geomagnetic pole where auroras most often occur). SMILE will also gather simultaneously in situ measurements with its two other instruments making up its payload – an ion analyser called LIA and a fluxgate magnetometer named MAG. These instruments will monitor the ions in the solar wind, magnetosheath and magnetosphere while detecting changes in the local DC magnetic field.
Orbit SMILE had to reach a high enough altitude to view the outside edge of Earth's magnetopause and at the same time obtain good spatial resolution of the auroral oval. The chosen orbit is therefore highly elliptical and highly inclined (73 degrees), and takes SMILE a third of the way to the Moon at apogee (an altitude of 19 Earth radii).
This type of orbit enables SMILE to spend much of its time (about 80%, equivalent to nine months of the year) at high altitude, allowing the spacecraft to collect continuous observations for the first time during more than 40 hours. This orbit also limits the time spent in the high-radiation Van Allen belts. SMILE was launched into low Earth orbit in May 2026 by a Vega-C launch vehicle from Kourou, French Guiana. Over the course of a month, its propulsion module brought the spacecraft to its nominal orbit, a polar orbit with apogee and perigee altitudes of 120,920 km above the North Pole and 5,027 km above the South Pole, respectively. When passing over Antarctica, the satellite transmits data to the German Antarctic Receiving Station, operated by DLR.
Spacecraft The SMILE spacecraft consists of a platform provided by CAS attached below a payload module provided by ESA. The CAS platform is composed of a propulsion and a service module, together with the two detectors of the LIA instrument. The payload module, built by Airbus, hosts 3 of the 4 scientific instruments and an X-band communications system.
Ground segment The SMILE ground segment comprises the Chinese Academy of Sciences (CAS) ground segment and the European Space Agency (ESA) ground segment, which collaborate closely on this mission. The Ground Support System (GSS) and the Science and Application System (SAS) are two important components of the CAS ground segment. The SAS is tasked with fostering collaboration between CAS and ESA, designing effective frameworks to coordinate scientists in planning SMILE science operations.
Instruments The spacecraft is equipped with four scientific instruments:
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