IXO's service module will contain the spacecraft systems such as telemetry and telecommand, attitude control, propulsion, and power distribution. The module will be a polygonal box constructed from a frame with a number of flat equipment panels bolted to it and a bottom panel. During integration and test, the equipment panels will fold down to allow access to the avionics modules mounted on their inner surfaces. The bottom panel will have a 2.4-metre diameter cutout in the centre, to allow the X-ray beam from the optics module to pass through to the instrument module.

The avionics boxes will be positioned on the anti-Sun side of the spacecraft in order to allow heat to be radiated to space. The Sun-facing panels will be fitted with thermal blankets.

The propellant tanks will be symmetrically positioned inside the service module, to minimise the movement of the spacecraft’s centre of gravity as the consumables are expended. Around 330 kg of propellant will be required for attitude control and station keeping at L2 over 10 years.

A geometrical mathematical model of the IXO service module with the fixed structure. Credit: ESA
Left: A propulsion tank. Right: Instrument control units. Credit: ESA

Also housed inside the service module will be five reaction wheels for fine attitude control, inertial reference units, the electrical power distribution system, command and data handling avionics boxes, a small battery, data recorders, and the Ka-band transmitter electronics.

On the exterior of the service module, several triads of thrusters will be mounted. These will be used for coarse attitude control and reaction wheel offloading. The high-gain Ka-band antenna used for communicating with Earth will also be mounted on the service module, as will the Attitude and Orbit Control System (AOCS) sensors (coarse and fine Sun sensors, star tracker).

Mechanical locks will secure the instrument module to the service module during launch.

	Fixed telescope structure
	Deployable telescope structure