ESA GNC Conference Papers Repository

Aeolus Attitude and Orbit Control Subsystem in-Flight Performance
Andrew Davies, Patrick Chapman, Andrew Hyslop
Presented at:
Virtual Conference 2021
Full paper:

Aeolus is the first spacecraft mission to demonstrate a novel technique to measure wind speed profiles on a global scale from space using a Lidar. Aeolus hosts a single payload, the Atmospheric Laser Doppler Instrument (ALADIN), which determines Doppler shifts of the backscatter from ultra-violet laser pulses fired at an angle toward the Earth, allowing the wind component along the horizontal line of sight to be determined. It is the 5th mission in ESA?s Earth Explorer program. The spacecraft was developed by Airbus, and was successfully launched into a 320 km Sun-synchronous dawn-dusk orbit by a Vega launcher in August 2018. Since early 2020 observational data has been used to improve weather forecasts and climate models. The AOCS is a bespoke design to deliver both pointing and safety requirements: ALADIN requires fine pointing for normal operations, with a steering law guidance profile that nominally provides zero Doppler shift for ground reflections of the laser, plus the telescope has short-term time limits for Sun-pointing. The AOCS consists of four active modes: Initial Acquisition Mode, Normal Mode, Thruster Control Mode, and Safe Mode. The sensor suite consists of Autonomous Star Trackers, an Inertial Measurement Unit, a Coarse Earth and Sun Sensor, Magnetometers, GPS receivers, and a single Rate Measurement Unit - used in Safe Mode. The actuation is provided by Reaction Wheels, Magnetorquers and thrusters ? also used to perform orbital manoeuvres.