1,806 research outputs found
Mission Planning Techniques for Cooperative LEO Spacecraft Constellations
This research develops a mission planning approach that allows different systems to cooperate in accomplishing a single mission goal. Using the techniques described allows satellites to cooperate in efficiently maneuvering, or collecting images of Earth and transmitting the collected data to users on the ground. The individual resources onboard each satellite, like fuel, memory capacity and pointing agility, are used in a manner that ensures the goals and objectives of the mission are realized in a feasible way. A mission plan can be generated for each satellite within the cooperating group that collectively optimize the mission objectives from a global viewpoint. The unique methods and framework presented for planning the spacecraft operations are flexible and can be applied to a variety of decision making processes where prior decisions impact later decision options. This contribution to the satellite constellation mission planning field, thus has greater applicability to the wider decision problem discipline
Self-organising satellite constellation in geostationary Earth orbit
This paper presents a novel solution to the problem of autonomous task allocation for a self-organizing satellite constellation in Earth orbit. The method allows satellites to cluster themselves above targets on the Earth’s surface. This is achieved using Coupled Selection Equations (CSE) - a dynamical systems approach to combinatorial optimization whose solution tends asymptotically towards a Boolean matrix describing the pairings of satellites and targets which solves the relevant assignment problems. Satellite manoeuvers are actuated by an Artificial Potential Field method which incorporates the CSE output. Three demonstrations of the method’s efficacy are given - first with equal numbers of satellites and targets, then with a satellite surplus, including agent failures, and finally with a fractionated constellation. Finally, a large constellation of 100 satellites is simulated to demonstrate the utility of the method in future swarm mission scenarios. The method provides efficient solutions with quick convergence, is robust to satellite failures, and hence appears suitable for distributed, on-board autonomy
Energy-Efficient Design of Satellite-Terrestrial Computing in 6G Wireless Networks
In this paper, we investigate the issue of satellite-terrestrial computing in
the sixth generation (6G) wireless networks, where multiple terrestrial base
stations (BSs) and low earth orbit (LEO) satellites collaboratively provide
edge computing services to ground user equipments (GUEs) and space user
equipments (SUEs) over the world. In particular, we design a complete process
of satellite-terrestrial computing in terms of communication and computing
according to the characteristics of 6G wireless networks. In order to minimize
the weighted total energy consumption while ensuring delay requirements of
computing tasks, an energy-efficient satellite-terrestrial computing algorithm
is put forward by jointly optimizing offloading selection, beamforming design
and resource allocation. Finally, both theoretical analysis and simulation
results confirm fast convergence and superior performance of the proposed
algorithm for satellite-terrestrial computing in 6G wireless networks
Methodologies for the analysis of value from delay-tolerant inter-satellite networking
In a world that is becoming increasingly connected, both in the sense of people and devices, it is of no surprise that users of the data enabled by satellites are exploring the potential brought about from a more connected Earth orbit environment. Lower data latency, higher revisit rates and higher volumes of information are the order of the day, and inter-connectivity is one of the ways in which this could be achieved. Within this dissertation, three main topics are investigated and built upon. First, the process of routing data through intermittently connected delay-tolerant networks is examined and a new routing protocol introduced, called Spae. The consideration of downstream resource limitations forms the heart of this novel approach which is shown to provide improvements in data routing that closely match that of a theoretically optimal scheme. Next, the value of inter-satellite networking is derived in such a way that removes the difficult task of costing the enabling inter-satellite link technology. Instead, value is defined as the price one should be willing to pay for the technology while retaining a mission value greater than its non-networking counterpart. This is achieved through the use of multi-attribute utility theory, trade-space analysis and system modelling, and demonstrated in two case studies. Finally, the effects of uncertainty in the form of sub-system failure are considered. Inter-satellite networking is shown to increase a system's resilience to failure through introduction of additional, partially failed states, made possible by data relay. The lifetime value of a system is then captured using a semi-analytical approach exploiting Markov chains, validated with a numerical Monte Carlo simulation approach. It is evident that while inter-satellite networking may offer more value in general, it does not necessarily result in a decrease in the loss of utility over the lifetime.In a world that is becoming increasingly connected, both in the sense of people and devices, it is of no surprise that users of the data enabled by satellites are exploring the potential brought about from a more connected Earth orbit environment. Lower data latency, higher revisit rates and higher volumes of information are the order of the day, and inter-connectivity is one of the ways in which this could be achieved. Within this dissertation, three main topics are investigated and built upon. First, the process of routing data through intermittently connected delay-tolerant networks is examined and a new routing protocol introduced, called Spae. The consideration of downstream resource limitations forms the heart of this novel approach which is shown to provide improvements in data routing that closely match that of a theoretically optimal scheme. Next, the value of inter-satellite networking is derived in such a way that removes the difficult task of costing the enabling inter-satellite link technology. Instead, value is defined as the price one should be willing to pay for the technology while retaining a mission value greater than its non-networking counterpart. This is achieved through the use of multi-attribute utility theory, trade-space analysis and system modelling, and demonstrated in two case studies. Finally, the effects of uncertainty in the form of sub-system failure are considered. Inter-satellite networking is shown to increase a system's resilience to failure through introduction of additional, partially failed states, made possible by data relay. The lifetime value of a system is then captured using a semi-analytical approach exploiting Markov chains, validated with a numerical Monte Carlo simulation approach. It is evident that while inter-satellite networking may offer more value in general, it does not necessarily result in a decrease in the loss of utility over the lifetime
SpaceRIS: LEO Satellite Coverage Maximization in 6G Sub-THz Networks by MAPPO DRL and Whale Optimization
Satellite systems face a significant challenge in effectively utilizing
limited communication resources to meet the demands of ground network traffic,
characterized by asymmetrical spatial distribution and time-varying
characteristics. Moreover, the coverage range and signal transmission distance
of low Earth orbit (LEO) satellites are restricted by notable propagation
attenuation, molecular absorption, and space losses in sub-terahertz (THz)
frequencies. This paper introduces a novel approach to maximize LEO satellite
coverage by leveraging reconfigurable intelligent surfaces (RISs) within 6G
sub-THz networks. The optimization objectives encompass enhancing the
end-to-end data rate, optimizing satellite-remote user equipment (RUE)
associations, data packet routing within satellite constellations, RIS phase
shift, and ground base station (GBS) transmit power (i.e., active beamforming).
The formulated joint optimization problem poses significant challenges owing to
its time-varying environment, non-convex characteristics, and NP-hard
complexity. To address these challenges, we propose a block coordinate descent
(BCD) algorithm that integrates balanced K-means clustering, multi-agent
proximal policy optimization (MAPPO) deep reinforcement learning (DRL), and
whale optimization (WOA) techniques. The performance of the proposed approach
is demonstrated through comprehensive simulation results, exhibiting its
superiority over existing baseline methods in the literature
Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View
Small satellite systems enable whole new class of missions for navigation,
communications, remote sensing and scientific research for both civilian and
military purposes. As individual spacecraft are limited by the size, mass and
power constraints, mass-produced small satellites in large constellations or
clusters could be useful in many science missions such as gravity mapping,
tracking of forest fires, finding water resources, etc. Constellation of
satellites provide improved spatial and temporal resolution of the target.
Small satellite constellations contribute innovative applications by replacing
a single asset with several very capable spacecraft which opens the door to new
applications. With increasing levels of autonomy, there will be a need for
remote communication networks to enable communication between spacecraft. These
space based networks will need to configure and maintain dynamic routes, manage
intermediate nodes, and reconfigure themselves to achieve mission objectives.
Hence, inter-satellite communication is a key aspect when satellites fly in
formation. In this paper, we present the various researches being conducted in
the small satellite community for implementing inter-satellite communications
based on the Open System Interconnection (OSI) model. This paper also reviews
the various design parameters applicable to the first three layers of the OSI
model, i.e., physical, data link and network layer. Based on the survey, we
also present a comprehensive list of design parameters useful for achieving
inter-satellite communications for multiple small satellite missions. Specific
topics include proposed solutions for some of the challenges faced by small
satellite systems, enabling operations using a network of small satellites, and
some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications
Surveys and Tutorial
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