Service Module attitude and orbit control (including propulsion)
The attitude and orbit control (including propulsion)
The Attitude and Orbit Control Subsystem (AOCS) is in charge of:
- automatic 3-axis control of the satellite attitude
- orbit control for which the needed thrust impulses are provided by the propulsion subsystem
- management of the propulsion subsystem
- automatic 1-axis control of the solar array orientation
- orienting the solar array towards the Sun in case of electrical anomaly
- providing ancillary attitude data to the Payload Module
The AOCS architecture is composed of four main assemblies:
- attitude measurement assembly comprising:
- digital Earth sensors (STD) for roll and pitch
- sun sensors (SSD) for yaw
- four independent two-axis gyros (two being in cold redundancy)
- wheels and magnetotorquers assembly comprising:
- three 40 Nms reaction wheels (RW)
- two magnetotorquers (MAC) able to generate a 315 Am2 magnetic moment
- the associated monitoring and command unit (EAIM)
propulsion and solar array drive mechanism assembly:
- the propulsion subsystem works in blow-down mode and it includes four pressurised tanks containing 300 kg of Hydrazine
- two branches of eight 23.5 N (initial inlet pressure of 22 bar) thrusters located on the SVM
- four latch valves, pressure transducers, fuel and gas valves for the propellant/pressurant loading/off-loading and pressurising/venting.
This assembly also includes the solar array drive mechanism (SADM) and the propulsion drive electronics (EPRM).
- safe mode assembly comprising:
- the safe mode dedicated electronics unit (T4S)
- the Sun Acquisition Sensors (SAS)
- the safe mode software
Last update: 21 June 2006
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