The simulation Tool for sHort and medium ORbital propagation (THOR) is a MATLAB/Simulink-based payload dispersion simulator which includes a numerical integrator to propagate the orbital dynamics of each payload and to propagate the launcher upper stage Euler rigid-body equations of motion.
The simulator is fully customizable in terms of mass, inertia properties and payloads number and position, in order to simulate many different launch configurations.
THOR is suitable for the optimization of the payload release sequence and timeline during a cluster launch in order to maximize the relative distance between the payloads during the release phase. This task is necessary to provide an assessment of compliance with respect to the international space debris mitigation guidelines endorsed by the main Space Agencies (e.g. ESA, NASA, JAXA) and the European Code of Conduct for Space Debris Mitigation.
The orbit propagation error was assessed though comparing the results with those obtained using ESA/ESOC’s space debris office propagation tool, based on the propagator of the ODIN software package, in the VEGA VV-01 qualification campaign framework. The simulator output analyzes the motion of each payload component and their potential mutual interference both in a short and medium time-scale.
Thanks to the experience acquired during the activity for the dispersion and collision avoidance analyses performed during VEGA VV-01 qualification, the THOR simulator has been used to provide the initial orbital elements by using the TLE format, in order to support all University teams in early orbit tracking operations.
The fully success of the VEGA VV-01 launch have qualified the THOR simulation tool by means of collision avoidance. Moreover the accurate spacecraft tracking experienced on all payloads of VEGA VV-01 during the first orbits performed by the AMSL (Alma Mater Satellite Laboratory), the Cubesat teams and the Amateur Radio community, fully validated also the procedure to generate the TLEs.