Speaker
Mr
Nuno Paulino
(GMV)
Description
The AADDTool - Analysis of Attitude Disturbances and Dynamics Tool – was developed to analyse the disturbances impacts on the dynamics of the spacecraft, start tracker blinding, wheels momentum unloading schemes, and solar power supply, for long term missions in meteorological missions for EUMETSAT. The configuration and setup of the mission is supported by a dedicated graphical interface, for fast configuration and seamless interaction with the simulator.
The paper presents its main features: it combines tiled 3D models for a cylindrical spacecraft (e.g. MSG) or any spacecraft with a central body and solar panels (e.g. MTG and METOP), with accurate models of space environment torques in line with ECSS standard. These were validated with independent tools or available flight/sensor data, and their tile-by-tile analysis of the disturbances allows the user to refine the contributions and take into consideration better approximations for shadowing. The implementation relies on developed libraries implemented in Matlab/Simulink, with a modular architecture to enable a modular design and progressive sophistication of the tool. All modules were validated unitarily using dedicated test setups with reference data (from independent tools, ground and flight data).
Foreseen continuous upgrading activity brought into AADDTool attitude dynamics propagation, spun guidance schemes, guidance programming, and the implementation of an elliptical field-of-view for the Star-Tracker analysis. Additional off-loading schemes were added for performance assessment of improved laws for wheels momentum management such as maximization of time between off-loading or scheduled off-loading with defined set points of the wheels speeds (or momenta).
For closed loop analysis and study of thrust firing parameterisation, the control loop MetOp was also implemented, including a pulse frequency modulator, dedicated to the thrusters' triggering management where the required torque is achieved by modulating the inhibition duration following a period of constant actuation. Before the study, implementations in the tool of two of the MetOp safe modes were successfully validated in terms of propellant mass and number of firing pulses, against simulated telemetry from the real flight software for Sun Safe Mode, and against data coming from LEOP telemetry (flight data) for Earth Safe mode.
The tool has been used for cases studies in LEO and GEO, to size disturbances and momentum management. The upgraded off-loading schemes have been compared with previous results in terms of offloading frequency and propellant consumption. Some results are presented.
The most recent study was for the MetOp scenario: analyse the impact of re-tuning the default thrusters grouping numbers according to mission phases or scenarios for improvement of propellant consumption, varying the lifecycle, solar activity, and initial conditions. The study used the on-board closed loop for two operating controlled modes: Earth pointing (FAM2) and Sun pointing (PRO). For this study, the MetOp spacecraft was modelled with a tiled 3D-model using a parallelepiped for main body and rotating solar array, used to perform a tile-by-tile contribution of the disturbance torques in LEO. The impact of the closed loop settings were analysed, and the main conclusions are summarized in terms of overall mass consumption, and firing and attitude histories.
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Primary author
Mr
Nuno Paulino
(GMV)
