Data Relay Satellite System Research Articles

NASA’s aerospace data relay satellite system development and its implications

NASA’s aerospace data relay satellite system development and its implications

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.

Comprehensive Evaluation on Space Information Network Demonstration Platform Based on Tracking and Data Relay Satellite System.

Due to the global coverage and real-time access advantages of the Tracking and Data Relay Satellite System (TDRSS), the demonstration platform based on TDRSS can satisfy the new technology verification and demonstration needs of the space information network (evolution from sensorweb). However, the comprehensive evaluation research of this demonstration platform faces many problems: complicated and diverse technical indicators in various areas, coupling redundancy between indicators, difficulty in establishing the number of indicator system layers, and evaluation errors causing by subjective scoring. Concerning the difficulties, this paper gives a method to construct this special index system, and improves the consistency of evaluation results with Analytic Hierarchy Process in Group Decision-Making (AHP-GDM). A comprehensive evaluation index system including five criterions, 11 elements, more than 30 indicators is constructed according to the three-step strategy of initial set classification, hierarchical optimization, and de-redundancy. For the inconsistent scoring of AHP-GDM, a high-speed convergence consistency improvement strategy is proposed in this paper. Moreover, a method for generating a comprehensive judgment matrix (the aggregation of each judgment matrix) aggregation coefficient is provided. Numerical experiments show that this strategy effectively improves the consistency of the comprehensive judgment matrix. Finally, taking the evaluation of TDRSS development as an example, the versatility and feasibility of the new evaluation strategy are demonstrated.

Serially concatenated extended CPM scheme based on TDRSS

Tracking and Data Relay Satellite System (TDRSS) can meet the needs of Low EarthOrbit (LEO) satellite real-time transmission, but it also has large Doppler shift, transmission delay and channel fading. Continuous Phase Modulation (CPM), with excellent properties of both bandwidth and energy efficient, are very suitable for nonlinear and/or fading channels such as satellite channel due to the constant envelope nature. In this paper, the CPE in the SCCPM scheme is replaced by the designed ECE to construct a new scheme called SCECPM scheme, in order to enhance the robustness of the signal. Compared with previous SCCPM scheme, the proposed system shows an improvement concerning the convergence threshold and bit-error-rate (BER).

A flexible LEO satellite modem with Ka‐band RF frontend for a data relay satellite system

SummaryFrom a geostationary Earth orbit (GEO) satellite's perspective, a low Earth orbit (LEO) satellite is visible on more than half of its orbit. Albeit the free‐space loss of an inter‐satellite link is much higher than the one of a direct ground link, considerable data rates and download volumes can be achieved. In this paper, we describe the system architecture of an integrated approach for a data relay satellite system and the development of LEO satellite and ground station modems. The approach allows serving several small and inexpensive LEO satellites at the same time both with low rate telemetry/telecommand links and with high rate download of sensor data.

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.

Towards the utilization of optical ground-to-space links for low earth orbiting spacecraft

The microwave spectrum has become a highly limited resource in satellite communications owing to an ever increasing demand for bandwidth and capacity. Therefore, a shift to the exploitation of optical carrier frequencies is currently underway. Focusing on high-rate transmissions of payload data from remote sensing satellites, operational systems, like the well-known European Data Relay Satellite system, are based on optical inter-satellite links. Besides, direct-to-earth free-space optical communications from low Earth orbiting spacecraft hold high potential for upcoming space missions through lower complexity. In that regard, we study the viability of the ground-to-space beacon laser signal of optical ground stations to be additionally modulated with tele-command tokens. Such an optical return channel could be variously put into use, for example to trigger automatic repeat requests of payload data downlinks, for jamming-free control of the spacecraft or for high-rate software uploads to its on-board processor. A particular challenge is posed by the unequal fading behavior of the optical channel regarding the down- and uplinks, which cover asymmetric optical pathways through the atmosphere.We define the end-to-end architecture of the communication chain including the transmitter on ground and the space-based receiver. Special attention is given to compatibility with established space data and system standards. Moreover, we examine the effects on the scheduling of satellite control, resulting from a constrained availability of the optical uplink due to cloud blockages. Our analysis aims at the employment of available space protocols for bidirectional optical communications with low earth orbiting spacecraft. Further on, we consider the adoption of upcoming standards to account for the optical fading channel. Certain applications like immediate automatic-repeat-requests for the downlink will require novel, optimized protocols.

Space VLBI: from first ideas to operational missions

The operational period of the first generation of dedicated Space VLBI (SVLBI) missions commenced in 1997 with the launch of the Japan-led mission VSOP/HALCA and is coming to closure in 2019 with the completion of in-flight operations of the Russia-led mission RadioAstron. They were preceded by the SVLBI demonstration experiment with the Tracking and Data Relay Satellite System (TDRSS) in 1986–1988. While the comprehensive lessons learned from the first demonstration experiment and two dedicated SVLBI missions are still awaiting thorough attention, several preliminary conclusions can be made. This paper addresses some issues of implementation of these missions as they progressed over four decades from the original SVLBI concepts to the operational status.

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.

Dynamic Relay Satellite Scheduling Based on ABC-TOPSIS Algorithm

Tracking and Data Relay Satellite System (TDRSS) is a space-based telemetry, tracking, and command system, which represents a research field of the international communication. The issue of the dynamic relay satellite scheduling, which focuses on assigning time resource to user tasks, has been an important concern in the TDRSS system. In this paper, the focus of study is on the dynamic relay satellite scheduling, whose detailed process consists of two steps: the initial relay satellite scheduling and the selection of dynamic scheduling schemes. To solve the dynamic scheduling problem, a new scheduling algorithm ABC-TOPSIS is proposed, which combines artificial bee colony (ABC) and technique for order preference by similarity to ideal solution (TOPSIS). The artificial bee colony algorithm is performed to solve the initial relay satellite scheduling. In addition, the technique for order preference by similarity to ideal solution is adopted for the selection of dynamic scheduling schemes. Plenty of simulation results are presented. The simulation results demonstrate that the proposed method provides better performance in solving the dynamic relay satellite scheduling problem in the TDRSS system.

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.

Special issue on main results of Call‐off Order 3 (CoO3) in SatNEx III

Special issue on main results of Call‐off Order 3 (<scp>CoO3</scp>) in <scp>SatNEx</scp> III

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.

Adaptive subsequence adjustment with evolutionary asymmetric path-relinking for TDRSS scheduling

Due to the limited transmission resources for data relay in the tracking and data relay satellite system (TDRSS), there are many job requirements in busy days which will be discarded in the conventional job scheduling model. Therefore, the improvement of scheduling efficiency in the TDRSS can not only help to increase the resource utilities, but also to reduce the scheduling failure ratio. A model of nonhomogeneous parallel machines scheduling problems with time window (NPM-TW) is firstly built up for the TDRSS, considering the distinct features of the variable preparation time and the nonhomogeneous transmission rates for different types of antennas on each tracking and data relay satellite (TDRS). Then, an adaptive subsequence adjustment (ASA) framework with evolutionary asymmetric path-relinking (EvAPR) is proposed to solve this problem, in which an asymmetric progressive crossover operation is involved to overcome the local optima by the conventional job inserting methods. The numerical results show that, compared with the classical greedy randomized adaptive search procedure (GRASP) algorithm, the scheduling failure ratio of jobs can be reduced over 11% on average by the proposed ASA with EvAPR.

China&amp;rsquo;s data relay satellite system served for manned spaceflight

On the basis of a description of data relay satellite system's out-standing advantages, the difficulties to be overcome and the key technologies to be mastered in the development(including precise acquisition and tracking technology, deployable dual-banded tracking antenna with very large electrical dimension, multiple control technology for satellite attitude control and antenna pointing, etc.) are analyzed in detail. The development course of Tianlian-1 data relay satellite system is introduced. This system, with China's characteristics, has 100 percent orbit coverage for MEO and LEO user-spacecrafts by setting the control stations in-country only. Its successful implementation has made China the second country in the world (USA first) in possession of such a system. Tianlian-1 data relay satellite system's success in supporting Shenzhou-7 to Shenzhou-10 spaceship, Tiangong-1 missions shows its important role, huge benefits and broad application prospects in space-based information transmission.

Reliability Growth Analysis of Satellite Systems

&#x0D; &#x0D; &#x0D; A reliability trend/growth analysis methodology for satellite systems is suggested. A satellite system usually consists of many satellites successively launched over many years, and its satellites typically belong to different satellite generations. This paper suggests an approach to reliability trend/growth data analysis for the satellite systems based on grouped data and the Power Law (Crow-AMSAA) Non- Homogeneous Poisson process model, for both one (time) and two (time and generation) variables. Based on the data specifics, the maximum likelihood estimates for the Power Law model parameters are obtained. In addition, the Cumulative Intensity Function (CIF) of a family of satellite systems was analyzed to assess its similarity to that of a repairable system. The suggested approaches are illustrated by a case study based on Tracking and Data Relay Satellite System (TDRSS) and Geostationary Operational Environmental Satellite (GOES) data.&#x0D; &#x0D; &#x0D;