Debris Attitude Motion Measurements and Modeling – Observation vs. Simulation

End of 2014, ESA initiated a research project named “Debris Attitude Motion Measurements and Modeling”. The main goal of this project was to combine space debris attitude state information, obtained by different means of observation, with numerical simulations. Under the lead of AIUB, light curves and laser ranging residuals were obtained by AIUB and IWF, while FHR conducted radar observations. In parallel, HTG developed a 6 degrees-of-freedom – orbit and attitude – propagator. This tool called ιOTA (In-Orbit Tumbling Analysis) takes into account all relevant external and internal perturbation sources (gravity, aerodynamics, solar radiation pressure, electro- magnetic, etc.). The final phase of the project was a critical comparison between observation data obtained for various space objects (e.g. ENVISAT, LAGEOS-2) and the corresponding simulation results. This comparison also served the purpose of software validation for ιOTA. The conversion of observation data into well-defined attitude states (i.e. rotation vector orientation and magnitude) can be quite difficult and sometimes resulting into multiple, non-unique solutions. Therefore, this comparison used an inverse approach. ιOTA is capable to convert its propagation results into synthetic observation results. This conversion takes into account the individual sensor type and relative perspective towards the observation target during the measurement campaign. This approach facilitates a direct comparison of real observation data (light curves, laser ranging residuals, and radar imaging) with the numerical propagation results. This paper presents the attitude propagation methods of ιOTA and the results of its software validation process showing a comparison between real and synthetic observation data.