• drag sail
• leo
• matlab
• orbital decay

Without proper mitigation strategies, the increase in artificial satellites in Low
Earth Orbit (LEO) causes a rise in space debris that is hazardous to operational
satellites and future missions. Among the possible mitigation strategies, there
are passive deorbiting devices capable of augmenting the exposed area and consequently increasing the atmospheric drag such as drag sails. Those devices are
considered effective and low-cost; therefore, they are relevant to comply with current guidelines on end-of-life disposal of satellites in LEO.
This thesis builds upon the work of a previous study, which analyzed the orbital
decay of a satellite in LEO equipped with a drag sail. The dacays are simulated
from various altitudes, for different solar activity conditions and for different values
of the area-to-mass ratio; but while the earlier analysis took into account only the
perturbative accelerations related to Earth’s oblateness and atmospheric drag, in
this study also the ones related to third-body gravitational attraction (of Sun and
Moon) and to solar radiation pressure have been considered. Moreover, as suggested by the conclusions of the previous work, this thesis introduces a simplified
treatment of attitude instability. The orbital dynamics has been simulated using
a MATLAB code, which is capable of integrating the Gauss variational equation,
while attitude instability has been simulated using an additional MATLAB script
which, by solving the Euler equations, allows simulation of the satellite’s attitude
variation under typical LEO disturbances. This makes it possible to compute an average value of the effective sail area exposed to the flow, which is then used in
the main simulation.
The results obtained indicate that for a controlled satellite the 5-year limit is not fulfilled for higher-altitude orbits (700 and 800 km) even for values of the A/m
ratio that are not particularly low and for lower orbits with low values of A/m.
In contrast, in the case of an uncontrolled satellite, this requirement is exceeded
much more frequently. It is worth noting that the case of uncontrolled satellite
has been studied using significant simplifications, therefore providing results that
are reliable only as a first approximation.