Solar sailing is a propulsion method which takes advantage of solar radiation pressure (SRP) as main source of thrust. However, around Earth, other sources also affect the solar-sail dynamics, including planetary radiation pressure (PRP) and atmospheric drag. In literature, the accelerations from SRP, PRP, and atmospheric drag are modeled using different theoretical and idealistic models, which make use of simplifying assumptions to describe the near-Earth dynamical environment, the sail’s geometry, and optical properties. Consequently, sailcraft in orbit experience accelerations different from the theoretically predicted ones. In order to quantify these discrepancies between the real and modeled solar-sail dynamics, a first definition and preliminary assessment of a set of calibration steering laws is provided in this paper. These steering laws allow to characterize the solar-sail acceleration at every sail orientation and to identify the contributions due to solar radiation pressure, planetary radiation pressure, and aerodynamic drag. The analyses presented make use of NASA’s upcoming ACS3 mission as baseline scenario and account for different possible orientations of its orbit. The results highlight the benefits and implementation challenges of each steering law and the impact that they have on the orbital elements, with particular focus on the orbital altitude. @en

This paper presents the design of solar-sail transfer trajectories to solar-sail displaced libration point orbits in the Earth- Moon system. The existence of families of solar-sail displaced libration point orbits in the Earth-Moon system has recently been demonstrated. These families originate from complementing the dynamics of the classical Earth-Moon circular restricted three-body problem with a solar-sail induced acceleration. Previous work has furthermore demonstrated the applicability of these orbits for high-latitude observation of the Earth and Moon. To not only demonstrate the existence and applicability of these orbits, but also their accessibility, this paper investigates the design of solar-sail transfers from Earth-bound parking orbits to a subset of these orbits. Initial guesses for the transfers are generated using reverse time propagation of the dynamics, where the control is provided by a locally optimal steering law. These initial guesses are subsequently used to initialize a 12th-order Gauss-Lobatto collocation method to satisfy a large number of constraints: departure from specific high Earth orbits, a minimum altitude with respect to the Earth and the Moon, and a maximum rotation rate of the solar sail. As an application of the developed methodology, this paper shows results for transferring two spacecraft to a constellation of displaced vertical Lyapunov orbits at the Earth-Moon L2 point. This constellation has been shown to provide continuous coverage of the lunar Aitken Basin and the lunar South Pole while maintaining a continuous line of sight with Earth. Sets of feasible trajectories for both spacecraft with identical launch conditions are produced in order for the constellation to be initiated using a single Soyuz launch. Such a Soyuz launch can deliver two 1160-kg spacecraft into the found transfer trajectories. One of the spacecraft subsequently requires a transfer time of 53.06 days to enter its constellation orbit, while the transfer of the other spacecraft takes 67.89 days. These results prove the accessibility of solar-sail displaced libration point orbits in the Earth-Moon system, thereby reaffirming the potential of solar-sail technology to enable novel scientific missions in the Earth-Moon system. @en