Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a planned joint venture mission between the European Space Agency and the Chinese Academy of Sciences to study the interaction between Earth's magnetosphere and the solar wind, while simultaneously monitoring the magnetosphere's plasma environment. Launch is expected at the end of 2021.

SMILE will be equipped to simultaneously capture images and movies of the magnetopause, polar cusps, and aurora. Traditionally, satellites have taken local measurements of different regions to build up a global picture of the magnetosphere. However, a recent discovery that the magnetosphere emits X-rays will allow SMILE to capture more comprehensive data than previous missions did through the analysis of these X-rays.

Key instruments on board the spacecraft will include:

The mission consists of a propulsion module and service module provided by the CAS, and a payload module containing all of the scientific instruments and an X-band communications system by the ESA. The launch will be conducted by ESA, while the Mission Operations Centre will be run by CAS; both organizations will jointly operate the Science Operations Centre.

The spacecraft is currently planned for launch in 2021 to a Molniya orbit with an apogee of 20 R_⊕ (Earth radii, where 1 R_⊕ = 6,371 km) using a Long March 2C rocket. Mission cost is estimated to be €92 million.

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