SMILE Mission Concept

SMILE is designed to provide large-scale, long-term imaging of the Sun-Earth interaction to enable us to understand how it drives geomagnetic activity and, ultimately, space weather.

Earth’s magnetic field is constantly being bombarded by charged particles flowing from the Sun into the heliosphere (the solar wind). This solar wind carries an Interplanetary Magnetic Field (IMF) and both the solar wind and IMF interact with Earth’s magnetosphere to create a region of space around the Earth called the magnetosphere. The interaction between the solar wind, IMF and magnetosphere drive geomagnetic disturbances, such as storms and substorms, that can be damaging to satellites and technology on the ground.

Previous missions, such as Cluster and Double Star, have passed through the magnetosphere into the magnetosheath enabling us to determine the location of the edge of the magnetosphere, the magnetopause and some of its dynamics. However, these in-situ detections can only tell us the location of part of the magnetopause as and when the spacecraft pass through it. Smile is different.

The solar wind carries with it heavy ions (e.g. iron and oxygen) which are highly charged. When these ions get close to the Earth, they can interact with Earth’s exosphere, an extension of our neutral atmosphere into space. In this interaction, the ions steal and electron from the neutral particles. As the electron de-excites in the ion, it emits a Soft X-ray. Since these particles cannot directly enter Earth’s magnetosphere, this emission occurs in the magnetosheath. Smile will image this emission, allowing us to see the shape and location of the edge of Earth’s magnetic field. At the same time, Smile will image Earth’s aurora to see how changes in Earth’s magnetic field result in dynamics in the northern lights.

Smile’s mission goals are:

  • What are the fundamental models of the dayside solar wind/magnetosphere interaction?
  • What defines the substorm cycle?
  • How do Coronal Mass Ejections (CME) driven storms arise and what is their relationship to substorms?

To answer these questions, Smile will take four instruments into a highly elliptical (1.8 x 20 RE), high inclination (~70 degree) orbit, spending most of its orbit above the northern polar region. The four instruments, the Soft X-ray Imager, the Ultraviolet Imager, the Light Ion Analyser and the Magnetometer, will provide remote sensing and in-situ measurements of the solar wind-magnetosphere interactions.