3,030 research outputs found
All-propulsion design of the drag-free and attitude control of the European satellite GOCE
No full textThis paper concerns the drag-free and attitude control (DFAC) of the European Gravity field and steady-state Ocean Circulation Explorer satellite (GOCE), during the science phase. GOCE aims to determine the Earth's gravity field with high accuracy and spatial resolution, through complementary space techniques such as gravity gradiometry and precise orbit determination. Both techniques rely on accurate attitude and drag-free control, especially in the gradiometer measurement bandwidth (5-100mHz), where non-gravitational forces must be counteracted down to micronewton, and spacecraft attitude must track the local orbital reference frame with micro-radian accuracy. DFAC aims to enable the gravity gradiometer to operate so as to determine the Earth's gravity field especially in the so-called measurement bandwidth (5-100mHz), making use of ion and micro-thruster actuators. The DFAC unit has been designed entirely on a simplified discrete-time model (Embedded Model) derived from the fine dynamics of the spacecraft and its environment; the relevant control algorithms are implemented and tuned around the Embedded Model, which is the core of the control unit. The DFAC has been tested against uncertainties in spacecraft and environment and its code has been the preliminary model for final code development. The DFAC assumes an all-propulsion command authority, partly abandoned by the actual GOCE control system because of electric micro-propulsion not being fully developed. Since all-propulsion authority is expected to be imperative for future scientific and observation missions, design and simulated results are believed to be of interest to the space communit
LONG-DISTANCE, DRAG-FREE, LOW-THRUST, LEO FORMATION CONTROL FOR EARTH GRAVITY MONITORING
No full textEmbedded Model Control application to drag-free and satellite-to satellite tracking
No full textThis paper describes the realization of a generic simulator for formation flying satellites, and the design and application of Embedded Model Control (EMC) to the spacecraft control, as potentially applicable to a constellation of drag-free satellites. They can be employed for scientific purposes: here it is presented the Satellite-Satellite Interferometry (SSI) mission for the measurement of the Earth's gravitational field harmonics, which will follow the incoming gravimetric mission GOCE and the gravitational wave observatory LISA. The core drag-free controller (DFC) was partly validated by Preliminary Design Review of GOCE mission, and particular emphasize is given to the acceleration observer and to the command computation law. The measurement model and mission requirements are also presented, followed by the simulation results of the DFC, tuned ad-hoc in order to obtain accurate aiming targe
NMPC-based guidance and control for autonomous high-thrust non-coplanar LEO-GEO missions
No full textThis paper presents a novel Nonlinear Model Predictive Control strategy for autonomous guidance and control in high-thrust quasi-impulsive maneuvers. A sparse-in-time thrust behavior is promoted within the performance index. Sparsity and bang-bang behavior are indeed important features in view of the propellant consumption reduction. The guidance and control algorithm takes advantage of the so-called Modified Equinoctial Orbital Elements, which allow a reduction of potential numerical singularities with respect to the standard Keplerian elements. As case study, a non-coplanar Low Earth Orbit - Geostationary Orbit transfer mission is presented. In this case study, we show the effectiveness of the proposed strategy, compared to other approaches derived from classical astrodynamics
NMPC-Based Guidance and Control for Earth Observation Missions
No full textIn the framework of Earth Observation missions, many space programmes have been focused on remote sensing the Earth, to observe events and phenomena which cannot be studied in-situ. A key role in this context is played by autonomous guidance systems. From this point of view, Nonlinear Model Predictive Control owns a great potential for the future of aerospace control and guidance systems thanks to its capability to accomplish jointly the guidance and control tasks, ensuring the minimization of a suitable performance index. In this paper, a novel Nonlinear Model Predictive Control framework for autonomous guidance and control with high-thrust quasi-impulsive maneuvers is presented. A key feature is the use of different kinds of orbital motion models as possible internal prediction models in the optimization algorithm. These models are based on: Cartesian Coordinates, Keplerian Orbital Elements and Modified Equinoctial Orbital Elements. The ESA Sentinel-2 mission is considered as a benchmark for the proposed framework. The obtained results show the effectiveness, in terms of propellant consumption and reference tracking, of using the Equinoctial Elements as internal model. This latter dynamics parametrization can also overcome possible singularities (affecting the Keplerian Elements) while reducing the
computational complexity
Scheduling of Satellite Constellation Operations in EO Missions Using Quantum Optimization
No full textAs Earth Observation (EO) missions advance towards Agile Earth Observation Satellites, the complexity of scheduling problems increases, posing challenges for traditional optimization methods. This paper investigates the potential of a quantum algorithm to address the scheduling problem in EO constellations. In particular, a novel formulation of the satellite constellation optimization problem is proposed, translating it into a Quadratic Unconstrained Binary Optimization (QUBO) problem, i.e., compliant with quantum solvers. Penalty functions are incorporated to optimize mission energy consumption. The formulated QUBO problem is then implemented and solved on a real quantum computer (a D-Wave Quantum Annealer). The performance provided by the quantum machine is compared with established classical meta-heuristic solvers like Simulated Annealing and Tabu Search. The results show that the proposed quantum optimization process achieves better results in terms of both solution quality and computational efficiency
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