The joint Solar Wind Magnetosphere Ionosphere Link Explorer (SMILE) mission, a collaboration between the European Space Agency and the Chinese Academy of Sciences, has officially begun scientific operations after releasing its first observations from space. The spacecraft, launched in May, has spent months in commissioning and is now approved to study Earth's magnetosphere in soft X-rays and ultraviolet light.
SMILE arrived in its highly elliptical orbit on June 20 following a launch atop a Vega-C rocket from Kourou, French Guiana, on May 19 at 03:52 UTC. The spacecraft performed 11 apogee-raising maneuvers and one perigee-raising maneuver to reach an orbit inclined by 73 degrees, with an apogee altitude of 120,920 kilometers and a perigee altitude of 5,027 kilometers. This orbit allows SMILE to spend about nine months of the year at high altitudes, enabling continuous observations of Earth's poles and magnetic field.
The mission carries four instruments: the Soft X-ray Imager (SXI), the UV Imager (UVI), the Light Ion Analyzer (LIA), and the Magnetometer (MAG). Together they will observe how solar storms, geomagnetic storms, and other space weather phenomena interact with Earth's magnetic field. The first UVI observations captured a full ring of auroras around the North Pole in ultraviolet light on July 24, just two weeks after the instrument was brought online. It is the first camera since 2008 to capture such a full auroral ring in ultraviolet light.
«The SMILE mission is a testament to the trust built between our teams, their dedication to excellence, and their determination to find solutions, whatever the challenge,» said ESA Director of Science Professor Carole Mundell. «SMILE is now approved to begin science operations. This is a very important milestone – a true pleasure to announce – and I am sure our excellent collaboration will deliver ground-breaking data to scientists around the world.»
Now that science operations have begun, the UVI will observe Earth's auroras for 45 hours at a time, offering the longest continuous observations of auroras from space in history. In the same period, the SXI instrument was brought online and collected soft X-ray observations of Cassiopeia A and a supernova remnant within the Large Magellanic Cloud. Those images confirmed the instrument is operating as expected, but the team noted that the SXI detects too much stray light when pointed at Earth.
Because SMILE is an Earth observation mission, engineers are adjusting instrument settings and sending new software to the spacecraft to address the issue. ESA designed the instrument with versatility and remote operation in mind, and the agency is working with the CAS SMILE team to resolve the problem as soon as possible. The current orbit has the spacecraft pointing farther away from Earth, and as the northern hemisphere moves into winter, less light will be emitted by the North Pole, reducing the stray-light problem.
That reduced light will reach a minimum in mid-October, when SMILE will use the SXI to capture its first good observation of the magnetopause, the point where the solar wind meets Earth's magnetic field, and the northern polar cusp, a hole within the magnetosphere over the North Pole where charged particles from the solar wind extend toward Earth's surface.
With science observations underway, SMILE's primary mission has begun. It is expected to last three years, with the potential for extensions if the spacecraft remains in good health. The mission's data is expected to improve understanding of space weather and its effects on Earth's magnetic environment.