Smile spacecraft specs

ESA is providing Smile’s payload module, which carries the scientific instruments, as well as the payload module equipment control unit and the communication channel that downlinks all the science data to the ground. The Chinese Academy of Sciences (CAS) is providing the spacecraft platform, which contains essential systems for power, spacecraft attitude control, and propulsion, as well as the communication channel that enables control and command of the satellite.

Dimensions: 2.8 × 2.8 × 3.5 m (stowed for launch), 4.8 × 9.8 × 3.5 m (deployed in orbit)

Mass: 707 kg (without propellant), 2300 kg (with propellant), 76 kg (instruments only)

Antennas and booms: Two antennas on the spacecraft platform will receive commands from Earth and transmit spacecraft housekeeping data to Earth. An antenna on the payload module will transmit all science data from the instruments back to Earth. A deployable 3-m-long boom will hold two in-situ magnetic sensors (MAG instrument) at its end, to reduce the influence of magnetic fields generated by the spacecraft on the instrument.

Solar panels: Two deployable solar arrays with a combined area of 4.1 square metres will supply power. The solar arrays and a set of lithium-ion batteries will together provide a total capacity of 60 Ampere-hours.

Communication and data transfer: Average data transfer to Earth of 32 gigabits per orbit, via two antennas.

Orientation control: Smile is a three-axis stabilised spacecraft, meaning that a number of spinning wheels (‘momentum wheels’) will be used to adjust its orientation in three directions and in relation to other celestial bodies. In addition, three star trackers and twelve 10-Newton thrusters will keep Smile in its desired location and orientation.

Thrust: Smile’s main engine can produce a thrust of 490 Newtons. Following launch with a rocket, this engine will bring the spacecraft to its operational orbit.

Orbit: Smile must reach a high-enough altitude above the North Pole to view the outside edge of Earth's magnetosphere, and at the same time take high-resolution images of the regions on Earth that experience auroras. To achieve this, the spacecraft will travel around Earth in a highly elliptical (2–20 Earth radii) and inclined (73°) orbit. In this orbit, Smile will spend about 80% of its time at a high altitude, and limit its time spent in the high-radiation Van Allen belts.

Instruments: Smile will carry four instruments: two imagers will operate respectively in ultraviolet and soft X-ray wavelengths; one in-situ instrument will measure the solar wind ions; and one in-situ magnetometer will measure the magnetic field carried by the solar wind. More on Smile’s instruments.