Solar wind Magnetosphere Ionosphere Link Explorer
Artist's impression of the SMILE spacecraft
Mission typeMagnetospheric mission
Mission duration3 years (nominal)[1]
Spacecraft properties
ManufacturerAirbus (payload module)
Launch mass2200 kg
Dry mass708 kg
Power850 W
Start of mission
Launch dateMay 2025 (planned)[2]
Launch siteKourou
Orbital parameters
Reference systemGeocentric
RegimeHighly elliptical orbit
Perigee altitude5,000 km
Apogee altitude121,182 km
Inclination70° or 98°
SMILE mission logo
Official insignia for the SMILE mission

Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a planned joint venture mission between the European Space Agency and the Chinese Academy of Sciences. SMILE will image for the first time the magnetosphere of the Sun in soft X-rays and UV during up to 40 hours per orbit, improving our understanding of the dynamic interaction between the solar wind and Earth's magnetosphere.[3][4] The prime science questions of the SMILE mission are

As of October 2023, SMILE is expected to launch in May 2025.[2]


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 (LIA) and a magnetometer (MAG). These instruments will monitor the ions in the solar wind, magnetosheath and magnetosphere while detecting changes in the local DC magnetic field.

SMILE must 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 (70 or 98 degrees depending on the launcher), and takes SMILE a third of the way to the Moon at apogee (an altitude of 121 182 km, i.e. 19 Earth radii or RE). 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 40h. This orbit also limits the time spent in the high-radiation Van Allen belts, and in the two toroidal belts. SMILE will be injected into a low Earth orbit by a Vega-C launch vehicle from Kourou, French Guiana, and its propulsion module will bring the spacecraft to the nominal orbit with perigee altitude of around 5000 km.[1]

The SMILE spacecraft consists of a platform provided by the Chinese Academy of Sciences (CAS) attached to a payload module containing nearly all of the scientific instruments and an X-band communications system, provided by ESA. The payload module will be built by Airbus.[5] The platform is composed of a propulsion and a service module, together with the two detectors (or heads) of the ion instrument. The Mission Operations Center will be run by CAS; both organizations will jointly operate the Science Operations Center.


Key instruments on board the spacecraft will include:[3][1]

Working groups

Several working groups have been set up to help preparing the SMILE mission including

[Top] Simulation of SMILE soft X-ray images during a 52-hour orbital period. Pink rectangular boxes show two field-of-view candidates of the SMILE soft X-ray imager. [Bottom] SMLE orbit (pink ellipse), location (pink dots), and look direction (blue line) projected on the XZ plane (left), XY plane (middle), and YZ plane (right). Color contour shows plasma density on each planes. The OpenGGCM global magnetosphere - ionosphere model and one of SMILE orbit candidates are used for this simulation.

In-situ science working group

SMILE in-situ science working group is established to support the SMILE Team in ensuring that the mission science objectives are achieved and optimized, and in adding value to SMILE science. The in-situ SWG activity is centred on optimizing the design, the operations, calibrations planning, identifying the science objectives and opportunities of the in situ instrument package, including conjunctions with other magnetospheric space missions.

Modeling working group

The SMILE modeling working group provides the following modeling supports for the upcoming SMILE mission

1. Grand modeling challenge: MHD model comparison and SXI requirements/goals -

2. Boundary tracing from SXI data

3. Other science projects

Ground-based and additional science working group

The SMILE Ground-based and Additional Science Working Group coordinates support for the mission in the solar-terrestrial physics community. Their aim is to maximise the uptake of SMILE data, and therefore maximise the science output of the mission. They will coordinate future observing campaigns with other experimental facilities, both on the ground and in space, for example by using high resolution modes for Super Dual Auroral Radar Network facilities, or with EISCAT 3D, and correlating with data from other missions flying at the time. The working group is also developing a set of tools and a visualisation facility to combine data from SMILE and supporting experiments.

The Outreach working group

The SMILE Outreach working group aims to promote SMILE and its science among the general public, amateur science societies and school pupils of any age. Members of the group are active in giving presentations illustrating the science which SMILE will produce and the impact it will have on our knowledge of solar-terrestrial interactions. They generate contacts with organisations promoting science in primary and secondary schools, particularly in socio-economical deprived areas, hold hands-on workshops and promote careers in science. The group is focusing on SMILE as a practical example of how space projects are developed, and encouraging pupils to follow its progress to launch and beyond. It also promotes international exchanges, a good example of which is the translation of the book 'Aurora and Spotty' for children (and maybe for some adults too), originally in Spanish, into Chinese.

Space Lates at the National Space Centre
Jennifer Carter, University of Leicester, during her presentation

Result highlights











Following the success of the Double Star mission, the ESA and CAS decided to jointly select, design, implement, launch and exploit the results of a space mission together for the first time. After initial workshops, a call for proposals was announced in January 2015. After a joint peer review of mission proposals, SMILE was selected as the top candidate out of 13 proposed.[21] The SMILE mission proposal[22] was jointly led by the University College London and the Chinese National Space Science Center. From June to November 2015, the mission entered initial studies for concept readiness, and final approval was given for the mission by the ESA Science Programme Committee in November 2015. A Request For Information (RFI) on provisions for the payload module was announced on 18 December 2015. The objective was to collect information from potential providers to assess low risk payload module requirements given stated interest in the mission, in preparation for the Invitation to Tender in 2016.[23] The Mission System Requirements Review was completed in October 2018, and ESA Mission Adoption by the Science Programme Committee was granted in March 2019.[24] SMILE successfully completed the Spacecraft and Mission Critical Design Review (CDR) in June 2023 in Shanghai.[25]


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