Optimization of satellite constellation reconfiguration

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2003.Includes bibliographical references (p. 135-137).by Uriel Scialom.S.M

Analytical low-thrust satellite maneuvers for rapid ground target revisit

This paper presents an analytical solution for a low-thrust maneuver to reduce the flyover time of a given terrestrial target. The work extends the general solution previously developed by the authors for a 3-phase spiral transfer that results in a change in the relative right ascension of the ascending node and argument of latitude of satellites in a constellation, by varying the orbital period and the J2 effect experienced by each satellite. This work improves the accuracy of the existing method by including the periodic effects of J2 in the analytical solution. Using these improved equations, a calculation of the flyover time of a given latitude can be determined, and the passes for which the target longitude is in view identified. Validation against a numerical orbit propagator shows the analytical method to accurately predict the sub-satellite point of the satellite to within ±1° of longitude after 15 days. A case study is performed showing that the method can successfully be used to reduce the time of flyover of Los Angeles from 14 days to just 1.97 days, with a change of velocity (ΔV) of 63m/s. The full exploration of the solution space shows the problem to be highly complex, such that an increase in the ΔV used for a maneuver will not necessarily reduce the time of flyover, potentially making optimization using a numerical solution challenging. It also shows that very similar flyover times can be achieved with very different ΔV usage. As such, an overview of the solution space is extremely valuable in allowing an informed trade-off between the time of flyover and maneuver ΔV

Constellation Reconfiguration: Tools and Analysis

Constellation reconfi guration consists of transforming an initial constellation of satellites into some final constellation of satellites to maintain system optimality. Constellations with phased deployment, changing mission requirements, or satellite failures would all benefi t from reconfi guration capability. The constellation reconfiguration problem can be broken into two broad sub-problems: constellation design and constellation transfer. Both are complicated and combinatorial in nature and require new, more efficient methods. Having reviewed existing constellation design frameworks, a new framework, the Elliptical Flower Constellations (EFCs), has been developed that offers improved performance over traditional methods. To assist in rapidly analyzing constellation designs, a new method for orbit propagation based on a sequential solution of Kepler's equation is presented. The constellation transfer problem requires an optimal assignment of satellites in the initial orbit to slots in the final orbit based on optimal orbit transfers between them. A new method for approximately solving the optimal two-impulse orbit transfer with fixed end-points, the so-called minimum Delta v Lambert's problem, is developed that requires the solution of a 4th order polynomial, as opposed to the 6th or higher order polynomials or iterative techniques of existing methods. The recently developed Learning Approach to sampling optimization is applied to the particular problem of general orbit transfer between two generic orbits, with several enhancements specifi c to this problem that improve its performance. The constellation transfer problem is then posed as a Linear Assignment Problem and solved using the auction algorithm once the orbit transfers have been computed. Constellations designed for global navigation satellite systems and for global communications demonstrate signifi cant improvements through the use of the EFC framework over existing methods. An end-to-end example of constellation recon figuration for a constellation with changing regional coverage requirements shows the effectiveness of the constellation transfer methods

An analytical low-cost deployment strategy for satellite constellations

This work proposes a novel method for the deployment of a constellation of nano-satellites into Low Earth Orbit by using carrier vehicles to deliver the nano-satellites into the required orbit positions. The analytical solution presented allows for rapid exploration of the design space and a direct optimisation of the deployment strategy to minimise the time for complete constellation deployment. Traditionally, the deployment of satellite constellations requires numerous launches – at least one per orbital plane – which can be costly. Launching as a secondary payload may offer significant cost reductions, but this comes at the price of decreased control over the launch schedule and final orbit parameters. The analytical method presented here allows for the optimal positioning of the orbit planes of the constellation to be determined and the minimum time for deployment determined as a function of the manoeuvre ΔV. The effect of atmospheric drag on the manoeuvre propellant cost is also considered to ensure a realistic deployment scenario. A case study considering three constellation designs is presented which compares the cost of deployment using traditional launch methods with that of deploying the constellation using carrier vehicles. The results of this study show a significant reduction in cost when using the carrier vehicles on a dedicated launch, compared with launching the satellites individually. Most significantly, the launch cost when using carrier vehicles is primarily determined by the total number of satellites in the constellation, rather than the number of orbital planes. Thus, the carrier vehicle deployment strategy would allow for constellations with a large number of planes to be deployed for a fraction of the equivalent cost if traditional launch methods were used

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

Modeling and Optimization for Space Logistics Operations: Review of State of the Art

As "Space Mobility and Logistics" was listed as one of the five core competencies in the US Space Force's doctrine document, there is a growing interest in developing technologies to enable in-space refueling, servicing, assembly, and manufacturing as well as other in-space logistics operations. Modeling for space mobility and logistics requires a new approach that differs from conventional astrodynamics because it needs to consider the coordination of multiple vehicles to satisfy an overall demand; namely, the optimal trajectory of one vehicle does not necessarily lead to the optimal campaign solution that contains multiple vehicles and infrastructure elements. In addition, for in-space servicing applications, we need additional analysis capabilities to analyze and optimize the sizes of the fuel/spare depots and their inventory/sparing policies with orbital mechanics in mind. To tackle these challenges, there have been various attempts to leverage terrestrial logistics-driven techniques, coupled with astrodynamics, to enhance in-space operations; an earlier primary domain of interest was refueling and resource utilization for human space exploration, and more recent studies focus on in-space servicing, in-space manufacturing, and mega-scale constellations. This paper aims to provide a review of the literature by categorizing the state-of-the-art studies in two ways: (1) by application questions that are addressed; and (2) by logistics-driven methods that are used in the studies. The two categorizations are expected to help both practitioners and researchers understand the state of the art and identify the under-explored and promising future research directions.Comment: Submitted to AIAA SciTech Conference 202

Design and Operations of Satellite Constellations for Complex Regional Coverage

Fueled by recent technological advancements in small and capable satellites, satellite constellations are now shaping the new era of space commercialization creating new forms of services that span from Earth observations to telecommunications and navigation. With the mission objectives becoming increasingly complex, a new paradigm in the design and operations of satellite constellations is necessary to make a system cheaper and more efficient. This dissertation presents a set of novel mathematical formulations and solution methods that lend themselves to various applications in the design and operations of satellite constellation systems. The second chapter establishes the Access-Pattern-Coverage (APC) decomposition model that relaxes the symmetry and homogeneity assumptions of the classical global-coverage constellation design methods. Based on the model, this dissertation formulates an integer linear programming (ILP) problem that designs an optimal constellation pattern for complex spatiotemporally-varying coverage requirements. The third chapter examines the problem of reconfiguring satellite constellations for efficient adaptive mission planning and presents a novel ILP formulation that combines constellation design and transfer problems that are otherwise considered independent and serial in the state-of-the-art. Furthermore, the third chapter proposes a Lagrangian relaxation-based heuristic method that exploits the assignment problem structure embedded in the integrated design-transfer model. The fourth chapter extends the third chapter by investigating the multi-stage satellite constellation reconfiguration problem and develops two heuristic sequential decision-making methods based on the concepts of myopic policy and the rolling horizon procedure. This dissertation presents several illustrative examples as proofs-of-concept to demonstrate the value of the proposed work.Ph.D

Reconfigurable satellite constellations for geo-spatially adaptive Earth observation missions

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 145-151).Continuously increasing demand for Earth observation in atmospheric research, disaster monitoring, and intelligence, surveillance and reconnaissance (ISR) has been met by responsive architectures such as unmanned aerial systems (UAS) or artificial satellites. Space-based architectures can provide non-dominated design solutions on the utility-cost curve compared to alternate architectures through the use of two approaches: (1) reducing satellite manufacturing and launch costs and (2) introducing reconfigurability to the satellite constellations. Reconfigurable constellations (ReCons) enable fast responses to access targets of interest while providing global monitoring capability from space. The wide-area coverage and fast responses provided ReCon can complement high-resolution imagery provided by UAS. A newly proposed ReCon framework improves the model fidelity of previous approaches by utilizing Satellite Tool Kit (STK) simulations and Earth observation mission databases. This thesis investigates the design and optimization of ReCon in low Earth orbits. A multidisciplinary simulation model is developed, to which optimization techniques are applied for both single-objective and multi-objective problems. In addition to the optimized baseline ReCon design, its variants are also considered as case studies. Future work will potentially co-optimize ReCon and UAS-like systems.by Sung Wook Paek.S.M

A Framework for Orbital Performance Evaluation in Distributed Space Missions for Earth Observation

Distributed Space Missions (DSMs) are gaining momentum in their application to earth science missions owing to their unique ability to increase observation sampling in spatial, spectral and temporal dimensions simultaneously. DSM architectures have a large number of design variables and since they are expected to increase mission flexibility, scalability, evolvability and robustness, their design is a complex problem with many variables and objectives affecting performance. There are very few open-access tools available to explore the tradespace of variables which allow performance assessment and are easy to plug into science goals, and therefore select the most optimal design. This paper presents a software tool developed on the MATLAB engine interfacing with STK, for DSM orbit design and selection. It is capable of generating thousands of homogeneous constellation or formation flight architectures based on pre-defined design variable ranges and sizing those architectures in terms of predefined performance metrics. The metrics can be input into observing system simulation experiments, as available from the science teams, allowing dynamic coupling of science and engineering designs. Design variables include but are not restricted to constellation type, formation flight type, FOV of instrument, altitude and inclination of chief orbits, differential orbital elements, leader satellites, latitudes or regions of interest, planes and satellite numbers. Intermediate performance metrics include angular coverage, number of accesses, revisit coverage, access deterioration over time at every point of the Earth's grid. The orbit design process can be streamlined and variables more bounded along the way, owing to the availability of low fidelity and low complexity models such as corrected HCW equations up to high precision STK models with J2 and drag. The tool can thus help any scientist or program manager select pre-Phase A, Pareto optimal DSM designs for a variety of science goals without having to delve into the details of the engineering design process