Navigation Constellation Design Using a Multi-Objective Genetic Algorithm

In satellite constellation design, performance and cost of the system drive the design process. The Global Positioning System (GPS) constellation is currently used to provide positioning and timing worldwide. As satellite technology has improved over the years, the cost to develop and maintain the satellites has increased. Using a constellation design tool, it is possible to analyze the tradeoffs of new navigation constellation designs (Pareto fronts) that illustrate the tradeoffs between position dilution of precision (PDOP) and system cost. This thesis utilized Satellite Tool Kit (STK) to calculate PDOP values of navigation constellations, and the Unmanned Spacecraft Cost Model (USCM) along with the Small Spacecraft Cost Model (SSCM) to determine system cost. The design parameters used include Walker constellation parameters, orbital elements, and transmit power. The results show that the constellation design tool produces realistic solutions. Using the generated solutions, an analysis of the navigation constellation designs was presented

Spectrum Coexistence of LEO and GSO Networks: An Interference-Based Design Criteria for LEO Inter-Satellite Links

As small satellites become more capable through miniaturized electronics and on-board processing, constellations of low-cost satellites lunched in Low- Earth Orbit (LEO) become feasible. The increase in the number of LEO satellites drives the need for frequency coexistence between the LEO constellation systems with the already existing geostationary (GSO) satellite networks. In this context, it is crucial to design the communication links paying special attention to interference analysis. This is particularly true when the LEO satellite constellation exploit inter-satellite communication links (ISL). In this paper, a radio frequency interference analysis based on simulation of the dynamic satellite constellation is presented and the design parameters of the inter-satellite links are analyzed. The results suggest that carefully choosing the design parameters of the intersatellite links, spectrum coexistence of LEO and GSO networks may be possible.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Spectrum Coexistence of LEO and GSO Networks: An Interference-Based Design Criteria for LEO Inter-Satellite Links

As small satellites become more capable through miniaturized electronics and on-board processing, constellations of low-cost satellites lunched in Low- Earth Orbit (LEO) become feasible. The increase in the number of LEO satellites drives the need for frequency coexistence between the LEO constellation systems with the already existing geostationary (GSO) satellite networks. In this context, it is crucial to design the communication links paying special attention to interference analysis. This is particularly true when the LEO satellite constellation exploit inter-satellite communication links (ISL). In this paper, a radio frequency interference analysis based on simulation of the dynamic satellite constellation is presented and the design parameters of the inter-satellite links are analyzed. The results suggest that carefully choosing the design parameters of the intersatellite links, spectrum coexistence of LEO and GSO networks may be possible.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Design of a reconfigurable satellite constellation

This paper provides a fully analytical method to describe a satellite constellation reconfiguration manoeuvre. By making use of low-thrust propulsion and exploiting the Earth’s natural perturbing forces it is possible to analytically describe the reconfiguration of a constellation, achieving a desired separation of both Right Ascension of Ascending Node (RAAN) and Argument of Latitude between satellites. An inherent trade-off exists between the time taken for a manoeuvre and the required ΔV, however the analytical solution presented here allows for a rapid visualisation of the trade-space and determination of the ideal transfer trajectory for a given mission. The general method presented can be applied across a range of scenarios, including constellation deployment and repurposing. The results show that for a scenario with an initial orbit semi-major axis of 6878.14km, and a desired final semi-major axis of 6778.14km it is possible to achieve a separation of 180° argument of latitude between a manoeuvring and a non-manoeuvring reference satellite in approximately 68 hours with a ΔV of 200m/s. To achieve the maximum possible RAAN separation of 90° with a ΔV of 200m/s requires a much longer time of over 218 days. Using two manoeuvring satellites with the same total manoeuvre ΔV was found to be more efficient only for short manoeuvre times. This is quantified and for the case considered it is found that using a 2-satellite manoeuvre is advantageous when changing the argument of latitude and when changing the RAAN <10° approximately. The ability to identify this turning point clearly is a distinct advantage of the analytical solution presented

Time distributions in satellite constellation design

The aim of the time distribution methodology presented in this paper is to generate constellations whose satellites share a set of relative trajectories in a given time, and maintain that property over time without orbit corrections. The model takes into account a series of orbital perturbations such as the gravitational potential of the Earth, the atmospheric drag, the Sun and the Moon as disturbing third bodies and the solar radiation pressure. These perturbations are included in the design process of the constellation. Moreover, the whole methodology allows to design constellations with multiple relative trajectories that can be distributed in a minimum number of inertial orbits

Optimization of Reconfigurable Satellite Constellations Using Simulated Annealing and Genetic Algorithm

Agile Earth observation can be achieved with responsiveness in satellite launches, sensor pointing, or orbit reconfiguration. This study presents a framework for designing reconfigurable satellite constellations capable of both regular Earth observation and disaster monitoring. These observation modes are termed global observation mode and regional observation mode, constituting a reconfigurable satellite constellation (ReCon). Systems engineering approaches are employed to formulate this multidisciplinary problem of co-optimizing satellite design and orbits. Two heuristic methods, simulated annealing (SA) and genetic algorithm (GA), are widely used for discrete combinatorial problems and therefore used in this study to benchmark against a gradient-based method. Point-based SA performed similar or slightly better than the gradient-based method, whereas population-based GA outperformed the other two. The resultant ReCon satellite design is physically feasible and offers performance-to-cost(mass) superior to static constellations. Ongoing research on observation scheduling and constellation management will extend the ReCon applications to radar imaging and radio occultation beyond visible wavelengths and nearby spectrums. Keywords: Earth observation; remote sensing; satellite constellation; reconfigurability; repeat ground tracks; simulated annealing; genetic algorith

Comparative Assessment Of Different Constellation Geometries For Space-Based Application

As services from space are becoming an asset for life on Earth and the demand for data from space increases, the international interest in satellite constellations is increasingly growing. GPS (Global Positioning System) provides positioning and navigation. Iridium contains a relatively larger number of satellites for communication purpose. Molniya is a high elliptical orbits constellation providing high latitude coverage. Disaster Monitoring constellation consists of remote sensing satellites and brings responsiveness needed for emergencies. Recently, some companies, such as OneWeb, Samsung and Space-X, have made public their plan to deploy mega constellations of nanosatellites for global internet. Different constellation geometries have been proposed to meet various mission requirements, each one having specific advantages in terms of coverage, responsiveness, cost, etc. Thus, designing a constellation is a trade-off choice. The choice for a constellation is highly influenced by many factors, such as the system cost, the interaction with space environment (radiation and space debris), and the targeted terrestrial coverage. The design of a constellation requires selecting the parameters that best meet the mission requirements. To accomplish this, several studies on the comparison of satellite constellations proposed detailed analysis, e.g. the multi-criteria comparison for responsive constellations, the coverage assessment of elliptical constellations. However, most of them only focused on one or few performances, lacking of generalisation. A general study of constellation geometry can provide a basis for understanding the constellation design. This will allow the process of constellation design to be expedited by offering a proposal of an existing constellation style. This paper comparatively assesses different constellation geometries, including the classical proposed geometries and some less used configurations, and chooses the constellation geometry best suitable for a given mission (e.g. remote sensing, global internet). In this work, several parameters of constellation design will be considered to make a quantitative assessment: coverage (global or local), frequency of ground track repetition, responsiveness (i.e., how fast a satellite can be launched and the data return to Earth after launch), robustness to failure and speed of replenishment, end of life disposal, number of satellites and orbital altitude. The assessment will be conducted in a parametric approach. Each factor will be quantitatively evaluated by deriving a fitness function. Then, a series of weighting coefficients adapted to the given mission requirements will be chosen for the global fitness functions. Through multi objective optimisation, the constellation geometry best suitable for the given mission requirements will be derived

Phase Acquisition and Formationkeeping of a New Power Consumption Monitoring Satellite Constellation

A new satellite constellation proposed for global monitoring of electrical power consumption is described in the paper. The optimal small satellite constellation structure as well as its control accuracy required for serving the mission objective throughout the designed life span is examined. The orbital dynamics is analysed for the purposes of optimal phase acquisition and formationkeeping strategy design. A low-cost strategy for spreading all satellites onto their prescribed positions under both time and fuel consumption constraints is explained. The separation errors due to control system uncertainties are analysed, and the system requirements for the constellation phase acquisition are specified. A control strategy is investigated for keeping of the relative pattern of the constellation in spite of the perturbation effects from atmospheric drag and the potential harmonics of the non-spherical Earth, and fuel expenditure is minimised. The system feasibility is demonstrated via simulation results. The control system relies upon low-cost, practical flight-proven sensing and actuating systems for small satellite missions