Solar-Sailing Trajectory Design for Close-Up NEA Observations Mission

Near-Earth Asteroids (NEAs) are an extremely valuable resource to study the origin and evolution of the Solar System more in depth. At the same time, they constitute a serious risk for the Earth in the not-so-remote case of an impact. In order to mitigate the hazard of a potential impact with the Earth, several techniques have been studied so far and, for the majority of them, a good knowledge about the chemical and physical composition of the target object is extremely helpful for the success of the mission. A multiple-rendezvous mission with NEAs, with close-up observations, can help the scientific community to improve the overall knowledge about these objects and to support any mitigation strategy. Because of the cost of this kind of mission in terms of Dv, a solar sail spacecraft is proposed in this study, in order to take advantage of the propellantless characteristic of this system. As part of the DLR/ESA Gossamer roadmap, and thus considering the sailcraft based on this technology, the present work is focused on the search of possible sequences of encounters, with priority on Potentially Hazardous Asteroids (PHAs). Because of the huge amount of NEAs, the selection of the candidates for a multiple rendezvous is firstly a combinatorial problem, with more than a billion of possible sequences for only three consecutive encounters. Moreover, an optimization problem should be solved in order to find a feasible solar-sail trajectory for each leg of the sequence. In order to tackle this mixed combinatorial/optimization problem, the strategy used is divided into two main steps: a sequence search by means of heuristic rules and simplified trajectory models, and a subsequent optimization phase. Preliminary results were presented previously by the authors, demonstrating that this kind of mission is promising. In this paper, we aim to find new sequences by introducing a different approach on the sequence search algorithm and by reducing the area-to-mass ratio of the solar sail. A smaller area-to-mass ratio entails either the possibility to carry on more payload or to reduce the sail area, raising the TRL. A grid search over 10 years of launching dates is carried out, resulting in different sequences of objects depending on the departing date. Two sequences are fully studied and optimized. The mission parameters and trajectories of the sequences found are shown and explained

Multiple NEA Rendezvous Mission: Solar Sailing Options

The scientific interest in near-Earth asteroids (NEAs) and the classification of some of those as potentially hazardous asteroid for the Earth stipulated the interest in NEA exploration. Close-up observations of these objects will increase drastically our knowledge about the overall NEA population. For this reason, a multiple NEA rendezvous mission through solar sailing is investigated, taking advantage of the propellantless nature of this groundbreaking propulsion technology. Considering a spacecraft based on the DLR/ESA Gossamer technology, this work focuses on the search of possible sequences of NEA encounters. The effectiveness of this approach is demonstrated through a number of fully-optimized trajectories. The results show that it is possible to visit five NEAs within 10 years with near-term solar-sail technology. Moreover, a study on a reduced NEA database demonstrates the reliability of the approach used, showing that 58% of the sequences found with an approximated trajectory model can be converted into real solar-sail trajectories. Lastly, this second study shows the effectiveness of the proposed automatic optimization algorithm, which is able to find solutions for a large number of mission scenarios without any input required from the user

Multiple near-earth asteroid rendezvous mission: solar-sailing options

The scientific interest in near-Earth asteroids (NEAs) and the classification of some of those as potentially hazardous for the Earth stimulated the interest in their exploration. Close-up observations of these objects will drastically increase our knowledge about the overall NEA population. For this reason, a multiple NEA rendezvous mission through solar sailing is investigated, taking advantage of the propellantless nature of this propulsion technology. Considering a spacecraft based on the DLR/ESA Gossamer technology, this work focuses on a method for searching possible sequences of NEA encounters. The effectiveness of the approach is demonstrated through a number of fully-optimised trajectories. The results show that it is possible to visit five NEAs within 10 years with near-term solar-sail technology. Moreover, a study on a reduced NEA database demonstrates the reliability of the approach used, showing that 58% of the sequences found with an approximated trajectory model can be converted into real feasible solar-sail trajectories. Overall, the study shows the effectiveness of the proposed automatic optimisation algorithm, which is able to find solutions for a large number of mission scenarios without any input required from the user

Optimal options for rendezvous and impact missions to NEOs

In this paper some potentially interesting transfer options for missions to Near Earth Objects have been studied. Due to thehigh number of potential targets and to the large variety of possible missions that can be considered, especially if resorting to low-thrust propulsion, an extensive analysis of transfer options requires a preliminary approach oriented toward an effective global search, and an appropriately simplified trajectory transcription. Low-thrust options have been modeled through a novel shape-based approach and a global optimization method has been used to look for globally optimal transfers. Different targets have been identified and various mission scenarios have been considered: rendezvous, sample return missions both with and without Earth gravity assist and impact missions

Collision-aware Task Assignment for Multi-Robot Systems

We propose a novel formulation of the collision-aware task assignment (CATA) problem and a decentralized auction-based algorithm to solve the problem with optimality bound. Using a collision cone, we predict potential collisions and introduce a binary decision variable into the local reward function for task bidding. We further improve CATA by implementing a receding collision horizon to address the stopping robot scenario, i.e. when robots are confined to their task location and become static obstacles to other moving robots. The auction-based algorithm encourages the robots to bid for tasks with collision mitigation considerations. We validate the improved task assignment solution with both simulation and experimental results, which show significant reduction of overlapping paths as well as deadlocks