Data Relay Satellite Research Articles

State of the art and prospects for the development of onboard radio systems for deep space communications

Currently, due to the rapid exploration of interplanetary space, more and more missions are being sent to deep space, and they promise to generate an exponentially increasing amount of data in the form of complex scientific measurements, high-resolution images and video. As a response to these challenges, scientists' attention is focused on the possibilities of laser, or optical, communication due to its potential to exceed the bandwidth of radio channels. And although broadband laser communication for near-Earth orbit and satellites in lunar orbit has been verified, deep space creates new problems for it, which will not soon allow abandoning the radio range. Therefore, this article discusses both the results achieved and the prospects for using the radio band in promising deep space communication systems. The purpose of the work was to assess the current state and prospects for the development of onboard deep-space radio communication systems. Based on the analysis of performance of foreign space-based transponders, the current state and prospects for the development of on-board radio systems for deep space communications are determined. The frequency ranges of space communications are considered, predictive estimates for the development of signal-code structures are obtained and the prospects for using various modulation methods are defined. The SDST transponder application is considered in detail by the example of telecommunications unit of the Mars Reconnaissance Orbiter (MRO) data-relay satellite. The proposed forecast estimates can be used in the development of radio systems for deep space communications.

A Study of the Feasibility of Using Accompanying Data-Relay Satellites in the Tasks of Providing Communication with Deep-Space Spacecraft

A Study of the Feasibility of Using Accompanying Data-Relay Satellites in the Tasks of Providing Communication with Deep-Space Spacecraft

A Study of the Feasibility of Using Accompanying Data-Relay Satellites in the Tasks of Providing Communication with Deep-Space Spacecraft

We have considered possible architecture options for an interplanetary communication system in which a data relay is used. The structure of a typical space communication link and the ways to improve its efficiency are analyzed. As one possibility, it is proposed to use accompanying orbital data-relay satellites providing the required data-transmission rate in the mode of formation flight together with the research spacecraft (SC). The optimization of the heliocentric leg of the flight trajectory of the Martian research SC and its accompanying data-relay satellite was carried out. The principal possibility of providing a formation flight of the data-relay satellite and research SC to improve communication with the Earth is demonstrated. Estimates were obtained for the masses of data-relay satellite and research SC with regard to the use of medium-lift launch vehicle of Soyuz type and a Fregat booster. Estimates are given for an increase in the duration of high-speed communication due to the use of a data-relay satellite in libration points L4 and L5 of the Earth–Sun system, as well as in heliocentric circular orbits with different radii.

Dynamic scheduling method for data relay satellite networks considering hybrid system disturbances

System disturbances, such as the change of required service durations, the failure of resources, and temporary tasks during the scheduling process of data relay satellite network (DRSN), are difficult to be predicted, which may lead to unsuccessful scheduling of tasks. A high-efficiency and robust DRSN calls for smarter and more flexible disturbances elimination strategies. Here, we unify the above three system disturbances as temporary task arrival and extend the static scheduling model of DRSN. Specifically, we derive and define a scheduling model that unifies the static scheduling and dynamic scheduling processes. Meanwhile, we propose a k-step dynamic scheduling algorithm considering breakpoint transmission (k-steps-BT) to solve the above model. Based on the principle of backtracking algorithm and search tree, k-steps-BT can eliminate disturbances quickly by rescheduling tasks and can determine the rescheduling scheme when temporary tasks arrive. Finally, extensive experiments are carried out to verify the proposed model and algorithm. The results show that the proposed model and algorithm can significantly improve the task completion rate of dynamic scheduling without drastic adjustments to the static scheduling scheme.

Distributed Coordination of Space–Ground Multiresources for Remote Sensing Missions

As data relay satellites (DRSs) play an increasingly important supporting role in remote sensing missions, efficient coordination across space–ground multiresources becomes a significant problem. Owing to the implementation problem of the centralized coordinate methods, this paper studies a distributed coordinate resource scheduling method which is realizable in the current space network structure. To be specific, we first formulate the multiple resource coordination problem into an MILP problem based on a modified time-expanded graph. Then, the problem is transferred and decomposed into subproblems for remote sensing satellite (RSS) systems and DRS systems to solve distributedly. Afterwards, we propose a distributed iterative scheme for the RSS systems and DRS systems based on alternating direction method of multipliers (ADMM), in which only the schedule information of the inter-satellite links are required to exchange between RSS systems and DRS systems. Simulation results are provided to validate the effectiveness of our distributed coordinated resource scheduling algorithm.

Task Scheduling Under a Novel Framework for Data Relay Satellite Network via Deep Reinforcement Learning

Data relay satellite networks (DRSNs) face the challenge of increasing relay mission demands in space networks. To improve the task scheduling efficiency of DRSN further, we propose a novel task scheduling framework, wherein a scheduling sequence is generated by selecting one antenna and selecting one task for the antenna in each step. Subsequently, the task scheduling problem of DRSN (TSPD) is regarded as a sequential decision-making problem and is optimized using a method based on deep reinforcement learning (DRL), which overcomes the difficulty of designing heuristics with massive efforts. In this study, a mathematical model and corresponding Markov decision model based on our proposed scheduling framework are constructed, and for the first time, a policy network that includes one encoder based on the attention mechanism and two decoders is designed to solve the TSPD. In addtion, extensive experiments are conducted to verify the effectiveness of our scheduling framework and demonstrate that the DRL method can obtain a scheduling scheme with the highest profits with decent generalization to different task scales, number of user spacecrafts and execution duration of tasks.

Traffic Load Optimization for Multi-Satellite Relay Systems in Space Information Network: A Proportional Fairness Approach.

Backbone satellites in a space information network (SIN) can be used as air base stations or data relay satellites (DRSs) to realize cross-system, cross-network and long-distance relay transmission. In this paper, a traffic load optimization problem for multi-satellite relay systems in SIN is considered to achieve highly efficient cooperative transmission and improve resource utility. A model of SIN based on a distributed satellite cluster (DSC) is considered, and the characteristics of the model are analyzed. Based on this, a hybrid resource management architecture combining distributed and central resources control schemes is proposed to realize a centrally controllable and distributed optimization of resources to meet various comprehensive service requirements. Two scenarios of multi-satellite relay systems in SIN are given, and traffic load optimization problems with joint bandwidth and power allocation for these two scenarios are formulated based on proportional fairness (PF) criterion to achieve traffic load balancing with considerable system capacity. The optimization problems in these two scenarios are proved to be a convex optimization problem with mathematical analysis, and the closed-form solutions of two problems in their dual domain are derived by dual transformation. With the closed-form solutions, two iterative algorithms based on the subgradient method are designed under the proposed hybrid resource management architecture to solve the problems in this paper. Simulation results show that the proposed schemes can effectively improve the upper bound of system capacity by resource sharing and cooperative relay, and it can balance the traffic load well with guarantees of a reasonable level system capacity compared with existing methods.

Beam Scheduling with Various Mission Demands in Data Relay Satellite Systems

Beam Scheduling with Various Mission Demands in Data Relay Satellite Systems

Investigations and proposals for data relay satellite systems

<p indent=0mm>After more than ten years of development, China’s data relay satellite (DRS) system has gradually become an efficient space-based information network infrastructure, which provides tracking services and high-bandwidth, near continuous, communications support for users’ many types of spacecraft placed in lower altitude than the geosynchronous orbit. With rapid increase in space activities over the past decades in China, the demand for the DRS system is growing evidently. This paper, mainly from the perspective of application, gives a comprehensive review on the DRS systems worldwide and summarizes the application status of China’s DRS system in these years. Then, we analyze the essence and difficulties of three key bottlenecks in actual DRS system and develop a set of comprehensive and effective solutions for those bottlenecks in the system resource management. Finally, on the basis of refining the application trends of such systems, we give some proposals for future construction and application of China’s DRS system, which includes further completing the system, enhancing the relay satellites’ capabilities, and improving the system operation efficiency. This paper aims to provide global perspectives and technical directions for decision-makers, scholars, and engineers related to the space information network. Moreover, for effectively solving the contradiction between the rapid growth of requirements and limited resources and promoting the capacity of China’s DRS system, we point out the most important development trends, challenges, and work proposals from the perspective of actual applications.

Navigator Notes

Navigator Notes

Delay-throughput tradeoff in satellite data relay networks with prioritized user satellites

The efficient antenna scheduling strategy for data relay satellites (DRSs) is essential to optimize the throughput or delay of the satellite data relay network. However, these two objectives conflict with each other since the user satellites (USs) with higher priorities take up more transmission time of DRSs' antennas for greater throughput but the USs storing more packets cause a severer waiting delay to the whole network. To balance the conflicting metrics for meeting the delay-throughput integrated requirements, we formulate the antenna scheduling as a stochastic non-convex fractional programming, which is challenging to be solved. For the tractability, we equivalently transform the fractional programming to a parametric problem and implement the Lyapunov drift to guarantee the constraint of mean rate stability. By proposing a delay and throughput tradeoff based antenna scheduling algorithm, we further transform the parametric problem to a solvable weight matching problem. Simulation results reveal the feasible region of the preference control parameter for integrated QoS cases and its variation relationship with network delay and throughput.

Surface catalysis effects on mitigation of radio frequency blackout in orbital reentry

Radio frequency (RF) blackout during atmospheric reentry leads to the cutoff of communication with ground stations and/or data-relay satellites. This causes significant problems during reentry, and thus, mitigation methods have been in high demand. In this study, we numerically demonstrate a novel method for mitigating the RF blackout using surface catalysis effects. Plasma flow behavior and electromagnetic wave propagation around a reentry vehicle were investigated in detail. The approach couples computational fluid dynamics and a frequency-dependent finite-difference time-domain method. The computations were performed with a massive parallelization technique using a large computer. The computed results were compared for cases imposing low and full catalysis conditions on a surface boundary. The investigation revealed that the surface catalysis effects reduce the RF blackout. Atomic species, dissociated across a shock wave formed in front of the vehicle, were recombined on the vehicle surface through surface catalysis. These molecules, flowing into a wake region at the vehicle’s rear, caused recombinations of electrons, originally generated in the shock layer. Therefore, a decrease in electrons was observed in the wake region and a wake path, which allows the propagation of electromagnetic waves, was formed. This complicated behavior of the molecules and electrons, induced by the surface catalysis, resulted in mitigation of the RF blackout.

An enhanced MAC protocol based on the IEEE 802.11 for data relay satellite systems

SummaryData relay satellite (DRS) systems play an important role in space information networks. Characterized by highly dynamic topology and discontinuous communication links, it is suggested that the IEEE 802.11 protocol employed in such a network could be more flexible. However, such a terrestrial network protocol could not be applied to DRS systems directly, nor supports a fast response due to the long propagation delay and severe packet collision. To address this challenge, we proposed an enhanced media access control (MAC) protocol based on the IEEE 802.11 protocol providing multiaccess for low earth orbit (LEO) distributed constellations. In this paper, we investigated the access delay performance of the proposed protocol in our model. Then, we derived a contention window adaption by using an iteration algorithm that can dynamically adjust the values of the contention window depending on the number of user satellites in the communication coverage. Simulation results show that the average access delay does not exceed 20 seconds, which is significantly lower than the standard protocol. Moreover, the traffic threshold is increased to 0.6, and the maximum throughput has doubled compared with the standard protocol. It is proved that the enhanced MAC protocol shows a better performance in DRS systems.

Minimum-Time Attitude Maneuver and Robust Attitude Control of Small Satellite Mounted with Data Relay Communication Antenna

This paper proposes a nonlinear control method for carrying out Minimum-time satellite attitude maneuver and antenna motion which have robustness against model uncertainty. In recent years, small Earth observation satellites have been utilized and expected to maneuver rapidly in missions such as multi-target acquisition. On the other hand, small satellites need to send the observation data to ground station. Recently, small Earth observation satellites acquire high-resolution data, resulting in an increase in the time required for data communication. Thus, small satellites need to use inter-orbit communication link through Data Relay test satellite sending data from Data Relay communication (DRC) antenna. In conventional operations, the antenna motion is implemented after satellite attitude maneuver. However, this method has a time delay between the completion of the attitude maneuver and the start of data communication. The purpose of this study is to extend the time of earth observation and data communication by carrying out satellite maneuver and antenna motion concurrently. Because small satellite mounted with DRC antenna has large mass ratio of the antenna, we cannot ignore time variability of the moment of inertia of the whole system and reaction torque generated by antenna motion. Hence, in order to take the influence of the antenna motion into consideration, we combine a satellite attitude control system and an antenna drive system into one control system by governing equations and constructing the optimal control problem. We convert the optimal control problem into a NLP by discretizing the control input (a series of pulses) to minimize the final time of the total maneuver that includes the antenna adjustment. In addition, it is considered that a model uncertainty and unknown disturbance occurs in real space. Thus, we have to design feedback controller to secure robustness in model error and unknown disturbance. Accordingly in order to propose a nonlinear control method for carrying out minimum-time satellite attitude maneuver and antenna motion which have robustness against model uncertainty and unknown disturbance, we calculate a reference attitude by application of optimal control input torque to ideal satellite model and design servo controller by using state-dependent Riccati equation (SDRE) control method in order to track time-variant reference attitude.

High-Efficient Resource Allocation in Data Relay Satellite Systems With Users Behavior Coordination

In data relay satellite (DRS) systems, users compete for limited intersatellite link antenna beam (ILAB) resources of data relay satellites by submitting excessive service requests to the mission scheduling center (MSC), which leads to serious scheduling conflicts and considerably degrades the QoS (quality of service). Two key challenges, the effective mission scheduling, and the coordination of multiple users’ behaviors in submitting service requests, are involved in this issue. Most of the previous works have only focused on the mission scheduling issue, while neglecting the impact of users’ selfish behavior on the QoS. In this paper, we investigate the resource allocation problem in DRS systems from the perspective of users’ behavior analysis, i.e., joint coordination of users’ selfish behavior in submitting service requests and mission scheduling. Since those selfish users have no incentive to cooperate in the one-shot interaction, we construct a repeated game framework with a proper punishment and forgiveness strategy to maximize users’ payoffs and meanwhile to reduce the resource conflicts through a cooperative way. Moreover, an efficient cheat-proof mechanism is proposed to make users self-enforced to submit his/her actual resource requirement. Simulation results confirm that the proposed scheme can significantly improve the system operational performance. Compared with the payoffs under the Nash equilibrium in the one-shot game which is the main method of the current coordination scheme for DRS systems, our proposed joint method based on the repeated game framework can acquire 1.36 to 3.46 times gain in respect to 2 to 10 users, and also effectively decrease the resource conflicts.

A tradeoff resource allocation based on MF‐TDMA scheme in the multibeam data relay satellite systems

SummaryA tremendous increase in the number of distributed satellite constellations with the unscheduled burst data traffic will impose addition and diverse requirements on the DRS (data relay satellite) systems, which increases the complexity for beam management and affects a real‐time data return and acquisition. In this paper, we suggested that a large capacity can be achieved by a multibeam DRS system based on multifrequency time division multiple access scheme providing multiaccess for the distributed satellite constellations. Because the space‐based information network is characterized by the limited on‐board resources, a highly dynamic topology and time‐varying intersatellite links, we designed a 2‐stage dynamic optimization approach to separate the multiobjective optimization for frequency/time blocks and power, aiming at the rapidly converging to the optimal solution and at the same time meeting the fairness resource allocation. In particular, a capacity‐fairness tradeoff algorithm is proposed based on hybrid the enhanced genetic algorithm and the particle swarm optimization. Simulation results show that the tradeoff between maximizing total capacity and providing proportional fairness allocation is well balanced. The proposed algorithm can rapidly converge to adapt to the highly dynamic topology in data relay satellite systems.

Two-Phase Task Scheduling in Data Relay Satellite Systems

In data relay satellite (DRS) systems, one of the most important issues is the task scheduling. Most of the existing algorithms focused on the scenario of fixed task sets; however, the scheduled tasks can be constantly changing due to the various uncertain factors in the space environment. To deal with this challenge, we propose a two-phase task scheduling algorithm to enhance the performance of scheduling, including an initial scheduling phase and a dynamic scheduling phase. In the initial scheduling phase, we construct a scheduling model with multiple constraint conditions, and also design an improved genetic algorithm with elite reserved strategy and a crowding function to find the initial scheduling solution. While in the dynamic scheduling phase, we further investigate the possibility of task preemptive switching and decomposition, by constructing a dynamic scheduling model with multiple objectives, including maximizing the total weight of scheduled tasks, minimizing the change of the scheduling scheme, and minimizing the number of decomposed subtasks. Meanwhile, a preemptive dynamic scheduling algorithm (PDSA) is designed to solve the proposed dynamic scheduling model. Our simulation results show that the proposed PDSA is superior to the existing whole rescheduling algorithm in terms of the number of completed tasks, the rescheduling rate of scheme, as well as the processing time, which can significantly improve the performance of dynamic scheduling in DRS systems.

Design and Implementation of Hybrid Light and Microwave Switches Based on Wavelength Selective Switch for Future Satellite Networks

A hybrid switching node structure with light and microwave links is proposed, which is applicable to the future data relay satellite systems, aiming at the development trend of coexistence of light- link and microwave-link in the future. An experimental system for the light and microwave hybrid switching node based on wavelength selective optical switches (WSS) and optical transceiver modules, is established. It is shown by our experiment that this hybrid switching node can realize the dynamic bandwidth allocation and wavelength routing while the bit error rate of light link is less than 10?12, which provides a method for solving the hybrid switching problem of light-link and microwave-link on the future data relay satellite systems.

Integrated Tradespace Analysis of Space Network Architectures

Methods to design space communication networks at the link level are well understood and abound in the literature. Nevertheless, models that analyze the performance and cost of the entire network are scarce, and they typically rely on computationally expensive simulations that can only be applied to specific network designs. This paper presents an architectural model to quantitatively optimize space communication networks given future customer demands, communication technology, and contract modalities to deploy the network. The model is implemented and validated against NASA’s Tracking and Data Relay Satellite System. It is then used to evaluate new architectures for the fourth-generation Tracking and Data Relay Satellite System given the capabilities of new optical and Ka-band technologies, as well as the possibility to deploy network assets as hosted payloads. Results indicate that optical technology can provide a significant improvement in the network capabilities and lifecycle cost, especially when placing these terminals on board commercial satellites as hosted payloads. The cost savings and benefit improvements of such an architecture are discussed and quantified.

Communications satellites: Time expanded graph exploration of a tradespace of architectures

The choice of architecture in the design of large-scale complex systems has an enormous bearing on the cost, performance and adaptability of the system. It is often the case that the operational environment of the system changes over time, necessitating evolution of the architecture. In this paper, tradespace graphs of candidate space-based relay networks for NASA׳s Space Communication and Navigation (SCaN) program, focusing on the Tracking and Data Relay Satellite (TDRS) system, are analyzed in order to examine the potential pathways through the tradespace for a specified planning horizon. We utilize a method that enumerates architectures as vertices in a tradespace graph, taking into account both the fixed properties of the architecture and the variable ages of its assets. We then examine what real options can be put in place to enable future flexibility given uncertainty about the lifespan of existing TDRS assets. In a separate set of analysis, these time-expanded graphs are used to price the potential inclusion of hosted payloads against a range of possible architectural decisions.