Service module
The service module houses instruments needed for the basic control and operation of the satellite. It also supports the payload module by providing power, video data processing and data storage, and a means to relay data and commands to and from the ground stations, respectively.
It also comprises the sunshade and thermal tent to prevent the payload being exposed to sunlight and regulates the thermal stability of the spacecraft. During launch and the early operations phase, before the sunshade is deployed, power is supplied by a lithium-ion battery.
The service module also houses the communication subsystem, central computer and data handling subsystem, the high rate data telemetry, attitude control and star trackers. For telemetry and telecommand, low gain antenna up- and down-links with a few kbps capacity are employed. The high gain antenna used for the science telemetry down-link will be used during each ground station visibility period of an average of about 8 hours per day.
The service module also features the thrusters of the chemical propulsion system and the micro-propulsion system. The chemical propellant is used for the transfer to and injection into the final orbit around L2, and then to perform any small adjustments to the spacecraft’s orbit.
The micro-propulsion system uses nitrogen as propellant and serves to fine tune the satellite attitude and precisely control the spin rate.