Multi-objective optimisation of many-revolution, low-thrust orbit raising for Destiny mission

This work will present a Multi-Objective approach to the design of the initial, Low-Thrust orbit raising phase for JAXA’s proposed technology demonstrator mission DESTINY. The proposed approach includes a simplified model for Low Thrust, many-revolution transfers, based on an analytical orbital averaging technique, and a simplified control parameterisation. Eclipses and J2 perturbation are also accounted for. This is combined with a stochastic optimisation algorithm to solve optimisation problems in which conflicting performance figures of DESTINY’s trajectory design are concurrently optimised. It will be shown that the proposed approach provides for a good preliminary investigation of the launch window and helps identifying critical issues to be addressed in future design phases

Expanding Interplanetary Transfer Opportunities from Geostationary Transfer Orbits via Earth Synchronous Orbits

Geostationary transfer orbits (GTOs) are geocentric orbits widely considered for kick-stage operations of satellites for deep space missions. A piggyback spacecraft departing from GTOs requires a low transfer cost. The type of GTO and launch timings of piggyback missions, on the other hand, are typically determined by the primary mission that carried the piggyback spacecraft. This research introduces a new transfer strategy that coordinates piggyback spacecraft’s departure timing from Earth to deep space via an Earth synchronous orbit (ESO) after departure from a GTO. It also enables the spacecraft to change its velocity direction by introducing Earth gravity assists. Connecting several GTOs and interplanetary trajectories via ESOs reduces the ΔV required for the transfers. It leads to using transfer opportunities previously considered unsuitable for missions or miniaturizing the kick motor. As a result, ESOs allow for a broader launch opportunity for deep space piggyback probes. In addition, the feasibility of ESOs is shown numerically by comparing direct and ESO-assisted transfers from GTOs to Mars with the required Δ

A numerical simulation approach to the crater-scaling relationships in low-speed impacts under microgravity

The many small-body exploration missions that have occurred over the last few decades have shown that small solar system objects are covered with granular material of varying depth. These missions have also observed that granular materials are mobilized from the surfaces at speeds on the order of escape speed by different contributing mechanisms. Those result in various outcomes including escape and reimpact. The latter contributes to further impact-driven evolution. Despite the long history of the research in the field of planetary cratering, low-speed impacts have not been studied extensively under gravity levels relevant to small-bodies. Earth-based low-gravity platforms lack the ability to probe microgravity impact physics for a sufficiently long duration to collect meaningful data from experiments. In order to overcome these challenges, this study uses discrete-element method (DEM) simulations to test low-speed cratering at 5–50 cm/s in granular materials in microgravity. The study first presents a procedure for post-processing the raw simulation data to extract the information relevant to the crater-scaling relationships and demonstrates their applicability for crater sizes, ejecta properties and crater formation time. The implications of the results are discussed in the light of results from recent small-body exploration missions

Orbit Maintenance of Quasi-Satellite Trajectories via Mean Relative Orbit Elements

International audienceThe Martian Moons eXploration mission is currently under development at JAXA and will be the first spacecraft mission to retrieve pristine samples from the surface of Phobos. In preparation for the sampling operations, MMX will collect observations of Phobos from stable retrograde relative trajectories also known as quasi-satellite orbits or QSOs. This paper offers a semi-analytical analysis of mid-and high-altitude QSOs in terms of relative orbit elements. Our analysis is not limited to planar orbits and takes into account the eccentricity of the moon's orbit. Furthermore, we introduce a numerical map between mean and osculating orbit elements to study the long-term evolution of MMX and derive a Lyapunov control law for orbit maintenance purposes. The nonlinear controller is based on mean relative orbit element differences and tested with respect to injection errors