LUNISAT ORBIT MAINTENANCE AND LOW-THRUST MANEUVERS

Lunisat represents a next-generation microsatellite aimed at orbiting the Moon, and equipped with dispensers for the release of nanosatellites. This research is focused on orbital dynamics of the main microsatellite, and specifically address-es orbit maintenance and low-thrust maneuvers. Nonsingular equinoctial orbit elements are employed for orbit propagations, in conjunction with numerical av-eraging. This is a powerful technique for the numerical integration of the mean elements, and allows substantial computational improvements. Due to the mas-conian character of the lunar mass distribution, low altitude, near-circular lunar orbits are affected by a considerable number of harmonics of the Moon gravita-tional field. Thus, in the dynamical modeling a large number of harmonics are included, as well as the Earth and Sun perturbing influence as third bodies. Low-altitude lunar satellites turn out to impact the Moon surface after a few weeks or months. In case of unsatisfactory lifetime, two simple orbit maintenance strate-gies are evaluated, together with the related propellant budget. Moreover, mini-mum-time low-thrust transfers for reducing the orbit altitude are investigated, ei-ther for nanosatellite release or for the conclusive phase of the Lunisat mission, which finally terminates with the impact on the Moon surface.