Satellite constellation method to achieve desired revisit performance for multiple targets

The analytical model for Earth coverage by the satellites’ swath conforming to essential of discontinuous coverage, in contrast to continuous coverage, is presented. The analytic relations are consecutively derived for calculation of singleand multi-satellite Earth surface latitude coverage as well as for generating full set of typical satellite visibility zone time streams realized in the repeating latitude coverage pattern for given arbitrary satellite constellation. The analytic relations mentioned are used for developing the method for analysis of discontinuous coverage of fixed arbitrary Earth region for given satellite constellation using both deterministic and stochastic approaches. The method provides analysis of the revisit time for given satellite constellation, as a result of high speed (fractions of a second or seconds) computer calculations in a wide range of possible revisit time variations for different practical purposes with high accuracy which is at least on par with that provided by known numerical simulating methods, based on direct modelling of the satellite observation mission, or in a number of cases is even superior to it (due to the fact that when using the analytic procedures observation sessions cannot be missed). The method for synthesis of satellite orbits and constellations, optimized by given criterion (minimum of required number of satellites in the constellation, or minimum revisit time, or minimum of the satellites’ swath width required) for fixed parameters of on-board satellite equipment and constraints for unused criterion parameters of a list of mentioned above is presented. The numerical results demonstrate the possibilities of the methods developed for analyzing the given satellite constellation revisit time values distributed on the fixed Earth coverage area, and for synthesizing the satellite constellations in comparison with the traditional approaches based on constellation design in a priori fixed classes used for continuous coverage. Particularly, it is shown that the suggested method for synthesis of Secure Route Constellations, using deterministic and stochastic basis, directly leads to the optimized satellite constellations which provide consistently high performance and are at least on the same level, or better, in comparison with the best Walker constellations for discontinuous coverage.

SciSys, with the support of ESA’s ARTES-IV programme, is developing an integrated suite of Mission Management tools that support off-line mission planning and automated ground-based schedule execution. The Mission Management tool-set can be applied to a wide range of mission types with either periodic (pass-based) or permanent ground contact, and with single, multiple or constellations of satellites. The tool-set manages the planning of activities that are to be executed during satellite contact via ground-based automation and the commanding capabilities of the underlying mission control system, and also out-of-contact via schedules or time-tagged command queues loaded during a previous satellite contact for automatic execution on-board. Both ground-based and on-board schedules are generated from a common representation of operations tasks, activities and the constraints associated with them. The tool-set is designed to be independent of the underlying mission control system, with a configurable interface layer to support integration. The tool-set can be integrated with SciSys’ own UNiT product that supports automation of operations procedures. The tool-set also provides support for the generation of contact plans for constellations of MEO satellites, where there are multiple satellites and ground-stations. This includes both the generation of predicted visibilities from satellite orbit vectors, and the planning of available ground station resources to match contact requirements. A prime objective of the Mission Management development has been to provide a means of generating acceptable, rather than optimal, schedules, but doing this with a fast planning turn-around time and an approach that is scalable to support fleets and constellations of satellites. __________________________________________________________________________________

As a fundamental and significant stage of satellite networks which play an important role in global communications, a design of satellite constellations with inter-satellite links(ISLs) becomes necessary. An optimization method is proposed to determine both satellite elements and constellation elements using the multi-objective genetic algorithm(GA) in this paper. The objectives to be optimized, which are determined by the elements to be designed, are divided into performance objectives and cost objectives. The former consist of the coverage rate, the ISL range and the minimum elevation while the latter contain the total satellite count, the orbital altitude and the orbital inclination. With the aim of maximizing the performance minimizing the cost, the proposed method tries to achieve a balance among multi objectives and design specific satellite constellations considered in different conditions. Then the constellations designed in different schemes are compared with each other to demonstrate the correctness and effectiveness of the method.

The high number of objects in the LEO is a risk that collisions between sub-orbital or escape velocity objects with an orbiting object of satellites occur when two satellites collide while orbiting the earth. One of the approaches to avoid collisions is a robotic configuration of satellite constellations. Satellite constellations should not be confused with satellite clusters, which are groups of satellites moving in close proximity to each other in nearly identical orbits; nor with satellite series or satellite programs, which are generations of satellites launched successively; nor with satellite fleets, which are groups of satellites from the same manufacturer or operator that operate an independent system. CfEOS constellations designed for geospatial applications and Earth observation. Unlike a single satellite, a constellation can provide permanent global or near-global coverage anywhere on Earth. CfEOS constellations are configured in sets of complementary orbital planes and connect to ground stations located around the globe. This paper describes the GNC analysis, the orbit propagation and robotic systems configuration for Collision-free Earth observation satellites (CfEOS) constellations.

As a huge space system, satellite constellation is developing rapidly. Satellite constellation design is a basic problem in the design of multi spacecraft space system. It is the premise of building constellation of earth observation, satellite navigation, satellite communication and various scientific exploration satellites. According to the characteristics of modern satellite constellation design, this paper investigates the design and application of particle swarm optimization algorithm in satellite constellation, and the latest research progress of various research institutions in satellite constellation maintenance and control, autonomous navigation and space real-time monitoring, and discusses the latest strategies and technical methods of satellite constellation operation and management.KeywordsSatellite constellationParticle Swarm OptimizationLocalizationMappingPosition precision

The efficient modeling of communication networks and the impact of TCP/IP behavior in satellite constellations is an important study. The divergent properties of satellite networks are deployment height, motion, direction, link capacity which differ from one satellite constellations to another. So, certainly the behavior of TCP/IP which was designed for wired channels will considerably differ from one satellite constellations than another. In this paper, we are evaluating the performance of different TCP Congestion algorithms on 2 different satellite constellations, Iridium and Teledesic with respect to certain parameters. The three TCP congestion control algorithms, vegas, reno and bic are evaluated on the simulated satellite network and the performance of the three algorithms under different satellites constellation is measured using suitable metrics to improve the transmission of data packets over satellite links.

The Mars Science Laboratory (MSL) Telecom Operations Team at the Jet Propulsion Laboratory (JPL) has implemented an automated system for checking Comm Behavior Manager (CBM) window load sequences. CBM manages MSL's Telecommunications subsystem, and CBM windows are defined periods of time when the MSL spacecraft communicates either with Mars orbital assets via UHF or directly with Earth via X-Band. CBM windows must be verified against a long list of flight rules in order to enforce proper configuration of the Telecom subsystem and to ensure the spacecraft is operated in a safe way throughout the pass. In addition, the windows are verified against corresponding orbiter Telecom configurations for UHF passes or ground station configurations for X-Band passes in order to confirm agreement on both sides of the link. Errors in timing, geometry, or hardware configuration will result in a failed communication session, potentially preventing uplink of commands to the rover or delaying the return of critical data to the ground. Due to the complexity of the process in which dozens of windows must each be individually checked against many flight rules and against corresponding Earth station or orbiter configurations and timings, manual verification is an arduous task and highly susceptible to errors. The CBM window checking tool makes extensive use of a MySQL relational database to keep track of communications windows and to check their correctness in an automated and reliable way, eliminating many sources of error. Additionally, since CBM sequences must often be verified with a short turnaround when real-time changes to parameters, configuration, and timing are required during operations, it is important for the checking process to be swift in addition to reliable.

Large space-based communication networks have been growing in numbers of satellites, with plans to launch more than 10,000 satellites into Low Earth Orbit (LEO). While these constellations offer many advantages over ground-based communication systems, they pose a significant threat when they fail and generate space debris. Given the reliability of current satellites, engineers can use failure modeling to design satellite constellations that are more resilient to satellite failures. Several authors have analyzed the reliability of geostationary satellites, but few have expanded the work to multiple-satellite systems. To address this gap, we constructed a simulation model to show the performance of satellite constellations with different satellite reliability functions over time. The simulation model is broken down into four key parts: a satellite constellation model, a network model, a failure model, and a performance metric. We use a Walker star constellation, which is the most common constellation for LEO broadband satellite constellations. The network consists of satellite-to-satellite connections and satellite-to-groundstation connections, which routes data using a shortest-path algorithm. The failure model views satellites as either operational or failed (no partial failures) and considers the groundstation operator’s knowledge or lack thereof of the satellites’ operational status and uses satellite reliability to estimate the expected data throughput of the system. We also created a performance metric that measures how well the entire network is operating and helps us compare candidate constellations. We used the model to estimate performance for a range of satellite reliabilities, and for groundstations with different numbers of communication dishes (effectively, satellite-ground links). Satellite reliability is a significant contributing factor to the long-term constellation performance. Using the reliability of small-LEO satellites, we found that a constellation of 1,200 small-LEO satellites completely fails after less than 30 days, given that we do not consider partial failures. Satellite constellations with higher satellite reliability, such as large geostationary satellites, last less than 50 days. We expect the constellations in our model to perform worse than real satellite systems, since we are only modeling complete failures, however these findings provide a useful worst-case baseline for designing sustainable satellite constellations. We also found that the number of groundstation-to-satellite communication links at each groundstation is not a significant factor for more than five communication links, meaning that adding more communication antennas to existing satellite groundstations would not improve constellation performance significantly.

For many space missions using satellite constellations, symmetry of satellites distribution plays usually a key role. Symmetry may be considered in space and/or in time distribution. Examples of required symmetry in space distribution are in Earth observation missions (either, for local or global) as well as in navigation systems. It is intuitive that to optimally observe the Earth a satellite constellation should be synchronized with the Earth rotation rate. If a satellite constellation must be designed to constitute a communication network between Earth and Jupiter, then the orbital period of the constellation satellites should be synchronized with both Earth and Jupiter periods of revolution around the Sun. Another example is to design satellite constellations to optimally observe specific Earth sites or regions. Again, this satellites constellation should be synchronized with Earth’s rotational period and (since the time gap between two subsequent observations of the site should be constant) also implies time symmetry in satellites distribution. Obtaining this result will allow to design operational constellations for observing targets (sites, borders, regions) with persistence or assigned revisit times, while minimizing the number of satellites required. Constellations of satellites for continuous global or zonal Earth coverage have been well studied over the last twenty years, are well known and have been well documented [1], [2], [7], [8], [11], [13]. A symmetrical, inclined constellation, such as a Walker constellation [1], [2] provides excellent global coverage for remote sensing missions; however, applications where target revisit time or persistent observation are important lead to required variations of traditional designs [7], [8]. Also, few results are available that affect other figures of merit, such as continuous regional coverage and the systematic use of eccentric orbit constellations to optimize“hang time” over regions of interest. Optimization of such constellations is a complex problem and the general-purpose constellation design methodology used today is largely limited to Walker-like constellations. As opposed to Walker Constellations [1], [2], which were looking for symmetries in inertial reference frame, Flower Constellations [11] were devised to obtain symmetric distributions of satellites on rotating reference frames (e.g., Earth, Jupiter, satellite orbit). Since the theory of Flower Constellations has evolved with time the next section is dedicated to the summary of the theory up to the current status. The FCs solution space has been recently expanded with the Lattice theory [13], [14], encompassing all possible symmetric solutions.

This study provides a review of existing scientific works on the problem of scheduling heterogeneous orbital constellations. The relevance of planning the operation of such constellations is driven by several factors related to the rapid development of space technologies and the increasing number of satellites in orbit. Modern orbital constellations consist of spacecraft of various types designed to perform different tasks: Earth remote sensing, communications, navigation, and others. These satellites may belong to different opera tors and have varying technical specifications, which makes their efficient utilization extremely complex and labor-intensive. Furthermore, the planning of heterogeneous constellations is particularly relevant in the context of the growing number of commercial and government satellites, creating high competition for space resources. Rational planning enables minimizing costs, improving the quality of services provided, and enhancing the safety of spacecraft operations. In this regard, there has been a rapid increase recently in the number of spacecraft scheduling methods that can effectively account for the heterogeneity of orbital constellations and ensure their coordinated operation. This work continues the previously conducted review of publications released up to 2019 and focuses on the development of methods over the last five years, from 2019 to 2024. The study formulates the task of creating a digital platform that manages orbital constellations from different manufacturers to fulfill requests from users. An analysis of existing approaches to planning spacecraft constellations is carried out, highlighting their advantages and disadvantages, as well as evaluating their practical feasibility for solving the stated task. Based on the results of the analysis, conclusions are drawn regarding the need to develop a new approach to scheduling the operation of orbital constellations. Proposals are made for further research and development of methods and tools for spacecraft scheduling.

The wireless satellite communication system is considered to be the most promising new communication method to achieve the coverage of heaven, earth and sea. Satellite constellation design is the most important stage before the actual deployment of satellites. It will determine the number of satellites and orbit related parameters. We aim to study the constellation design of 5G low-orbit satellites. At present, some advanced research results have been proposed, providing important theory and experience for in-depth exploration and improvement of satellite constellation structure. We proposed a method based on the multi-objective particle swarm optimization (PSO) algorithm for designing low-orbit 5G satellite constellation. The method takes the number of satellites and orbit related parameters as the limit, and take the coverage of a specific area as the objective function. The results showed that the PSO algorithm can meet the full-time and full-area coverage low-orbit 5G constellation design for a specific area, and verified the effectiveness of the PSO algorithm for the coverage low-orbit 5G constellation design for the target area. We provided satellite constellation coverage guarantee for link-level simulation of 5g LEO satellite communication system in the next step.

Here, the networking aspects of the broadband satellite constellations are discussed, and the suitability of the constellations for multicast is assessed.

The African Space Agency aims to unify the available resources across the African Continent. One of these resources includes communication services and internet connectivity to cover African areas. To achieve this goal, this study proposes a standalone system, namely a satellite constellation system applying the Street of Coverage (SOC) method. This method includes three configurations, inclined orbit, symmetrical polar orbit, and non-symmetrical polar orbit. A Low Earth Orbit (LEO) is considered due to its advantage in its low latency, making it ideal for communication purposes. A mathematical model governing the SOC constellation is deduced. Results are visualized and analyzed using the System Tool Kit (STK) application. A validation case is proposed by comparing consistency with a well-known satellite constellation OneWeb produced by the international company Eutelsatgroup. Two potential satellite constellations are proposed to provide coverage across underserved African areas. In the first configuration, the symmetric polar constellation is utilized with 612 satellites uniformly distributed along 18 planes. This system is characterized by its low cost, high efficiency, and optimum performance as a standalone solution. In the second configuration, the equatorial satellite constellation with 25 satellites uniformly distributed along the equatorial plane is analyzed. This configuration is a more economical solution that uses fewer satellites and relies on back-hauling between available communication networks.

In recent years, the low-orbit satellites constellation has developed rapidly at home and abroad, involving navigation, remote sensing, communications, the internet and other fields. The performance of constellations will be influenced by multi-fold coverage heavily. For instance, remote sensing satellite constellations can improve the resolution of ground imaging through double coverage that two satellites can take ground photos get together at adjacent positions. There are more scholars studying continuous global coverage constellation, but less two-fold coverage or more. This article proposes the two-fold coverage width based on this hot demand about remote sensing satellite constellations, and proposes a constellation optimization design process. Then initial constellation parameters will be obtained from the single continue global coverage satellite constellation designed by the SOC method. The constellation will be optimized by the method proposed multiple iterations in this paper. Finally, the optimized constellations satisfied the function of two-fold coverage width and has better performance of the digital transmission opportunities to ground. The designed constellation satisfies the demand of two-fold coverage and has certain reference significance for engineering practice.

The way to solve the problem of satellite constellation design was outlined in the 1960s, recognizing the importance of satellite coverage (continuous or periodic) function and allowing interpretation of the operation of different types of space systems. Due to the fact that Earth periodic coverage optimization is extremely complex, for many years, the solutions of this problem have been searched for among a priori fixed constellation types successfully implemented before for continuous coverage, with continuous coverage seeming to be much easier than periodic coverage. In this study, it is shown that the technological advance in satellite constellation design for periodic coverage could be achieved by considering it as a unique and separate problem. The introduction in the route theory for satellite constellation design for Earth periodic coverage that aims at creating methods for optimization of arbitrary constellations, which is an alternative to the traditional approach that considers narrow classes of constellations to be analyzed, is described. The so-called route constellation is presented as a mathematical abstraction for approximation of arbitrary satellite constellation. The theory elements of the optimization procedure in the infinite domain of route constellations are introduced. Previously unknown regularities in Earth periodic coverage and in localization of optimal low-Earth-orbit satellite constellation parameters are presented and illustrated.