Extension of Earth-Moon libration point orbits with solar sail propulsion

This paper presents families of libration point orbits in the Earth-Moon system that originate from complementing the classical circular restricted three-body problem with a solar sail. Through the use of a differential correction scheme in combination with a continuation on the solar sail induced acceleration, families of Lyapunov, halo, vertical Lyapunov, Earth-centred, and distant retrograde orbits are created. As the solar sail circular restricted three-body problem is non-autonomous, a constraint defined within the differential correction scheme ensures that all orbits are periodic with the Sun’s motion around the Earth-Moon system. The continuation method then starts from a classical libration point orbit with a suitable period and increases the solar sail acceleration magnitude to obtain families of orbits that are parametrised by this acceleration. Furthermore, different solar sail steering laws are considered (both in-plane and out-of-plane, and either fixed in the synodic frame or fixed with respect to the direction of sunlight), adding to the wealth of families of solar sail enabled libration point orbits presented. Finally, the linear stability properties of the generated orbits are investigated to assess the need for active orbital control. It is shown that the solar sail induced acceleration can have a positive effect on the stability of some orbit families, especially those at the L2 point, but that it most often (further) destabilises the orbit. Active control will therefore be needed to ensure long-term survivability of these orbits

Novel solar sail mission concepts for high-latitude earth and lunar observation

This paper proposes the use of solar sail periodic orbits in the Earth-Moon system for observation of the high-latitudes of the Earth and Moon. At the Earth, the high-latitudes will be crucial in answering questions concerning global climate change, monitoring space weather events and ensuring sustainable development of these fragile regions. The polar regions of the Moon, especially the South Pole, are of great scientific interest as well as a potential destination for a future permanent lunar base. The existence of families of solar sail periodic orbits in the Earth-Moon system has previously been demonstrated by the authors and is expanded in this paper by introducing additional orbit families. The paper focuses in particular on orbits that are achievable with near-term solar sail technology and that originate by maintaining the solar sail at a constant attitude with respect to the Sun such that mission operations are greatly simplified. The results provide a set of constellations for continuous observation of the high-latitudes. For example, a constellation of two solar sail L2-displaced vertical Lyapunov orbits can achieve continuous observation of both the lunar South Pole and the centre of the Aitken Basin at a minimum elevation of 15 deg, while at the Earth, a set of two, so-called 'clover-shaped' orbits can provide continuous coverage of one of the Earth's Poles at 20 deg minimum elevation. Transferring these orbits to a higher-fidelity model, taking among others the eccentricity of the Moon into account, shows that these orbits still exist without any significant impact on their performance for high-latitude observation of the Earth and Moon

Design and Applications of Solar Sail Periodic Orbits in the Non-Autonomous Earth-Moon System

Solar sailing has great potential for a range of high-energy and long duration mis-sions in the Sun-Earth system. This paper extends this potential to the non-autonomous Earth-Moon system through the use of a differential correction scheme, and by selecting suitable in-plane and out-of-plane sail steering laws to develop new families of solar sail libration point orbits that are periodic with the Sun’s motion around the Earth-Moon system. New orbits include those that bifur-cate from the natural Lyapunov, halo and eight-shaped orbit families at the first and second Lagrange points. The potential of these orbits is demonstrated by con-sidering the performance of a subset of orbits for high-latitude Earth observations, lunar far-side communications, and lunar South Pole coverage