Cycler Orbits and the Solar System Pony Express

In this work, we explore the concept of a secondary “data mule” consisting of a small satellite used to ferry data from a Mars mission to Earth for downlink. The concept exploits the fact that two nearby optical communicators can achieve extremely high data rates, and that a class of trajectories called “cyclers” can carry a satellite between Mars and Earth regularly. By exploiting cycler orbits, the courier needs minimal onboard propulsion. However, cycler orbits have long periodicity, as it can take years for the satellite, Mars, and Earth to repeat their relative geometry. Therefore, we propose the use of a network of such cycler “couriers” on phase-shifted trajectories to achieve a regular cadence of downlink trips. We design a series of search and optimization steps that can output a set of trajectories that at first approximation have low onboard propulsion requirements and can be used for any regular logistics network to and from Mars, then derive the link budget for proximity optical communications to show that this network can ferry large amounts of data

Architecting space communication networks under mission demand uncertainty

NASAs Space Network has been a successful program that has provided reliable communication and navigation services for three decades. As the third generation of satellites is being launched, alternatives to the current architecture of the system are being studied in order to improve the performance of the system, reduce its costs and facilitate its integration with the Near Earth Network and the Deep Space Network. Within this context, past research has proven the feasibility of efficiently exploring a large space of alternative network architectures using a tradespace search framework. Architecting a space communication network is a complex task that requires consideration of uncertainty, namely (1) factoring in customer demand variability, (2) predicting technology improvements and (3) considering possible budgetary constraints. This paper focuses on adding uncertainty associated with (1) to the existing communications network architecture tool by describing a heuristic-based model to derive mission concept of operations (conops) as a function of communication requirements. The accuracy of the model is assessed by comparing real conops from current TDRSS-supported missions with the predicted concept of operations. The model is used to analyze how customer forecast uncertainty affects the choice of the future network architecture. In particular, four customer scenarios are generated and compared with the current TDRSS capabilities.United States. National Aeronautics and Space Administration (NNX11AR70G

Performance characterization of a multiplexed space-to-ground optical network

Advances in phased array systems for multi-beam free space optical communications are a key enabler for a new space-to-ground network architecture, namely a multiplexed optical architecture. The fundamental idea of a multiplexed space-to-ground optical network is the utilization of a multi-beam optical payload that allows each spacecraft to establish links with multiple ground stations within its line of sight. Information is then downlinked in parallel, from the satellite to the ground, through the subset of links not disrupted by clouds. In this paper we evaluate the performance of a multiplexed optical space-to-ground architecture from a systems perspective, with particular emphasis on the effect of cloud correlation in the network throughput. In particular, we first derive the expected data volume returned in a multiplexed architecture as a function of the optical network availability and the system total capacity. Then, we compare the performance of the proposed multiplexed architecture against a traditional single-beam downlink system that utilizes site diversity to mitigate cloud coverage effects. This comparison is based on two canonical scenarios, a global highly uncorrelated network representative of a geosynchronous satellite; and local, highly correlated, network representative of a low Earth orbit spacecraft. Through this analysis, we demonstrate that multiplexed architectures can improve the throughput of a space-to-ground optical network as compared to that of a single ground telescope without requiring a beam switching mechanism

Uncertainty quantification of network availability for networks of optical ground stations

This paper analyzes differences in the availability of networks of optical ground stations computed using different methods and datasets, and quantifies the uncertainty of the results. For that purpose, we first review existing methods proposed in the literature, and then existing cloud coverage datasets, and we compare the results obtained using different methods and datasets for several scenarios. Finally, we propose a new probabilistic global cloud coverage model that aggregates values from existing datasets and quantifies the uncertainty in measuring cloud probability, and present a method to compute the availability of a network of multiple optical ground stations, along with the corresponding uncertainty.Fundación Obra Social de La Caix

Observing Mars from Areostationary Orbit: Benefits and Applications

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Architecting near-earth space communication networks

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 119-122).Reliable communication and navigation services are critical to robotic and human space missions. NASA currently provides them through three independent and uncoordinated network that consist of both Earth-based and space-based assets, all managed under the Space Navigation and Communication Program. Nevertheless, the ever increasing mission requirements and funding limitations motivates the need of revising the current network architectures in order to identify areas of potential performance and cost efficiency improvements. The main objective of this thesis is to present a tool that helps decision-makers during the process of architecting a space communication network by (1) systematically enumerating and exploring the space of alternative network architectures, (2) identifying those with better performance and lower cost, and (3) providing traceability between the outputs of the tool and the architecting decisions. The tool is tailored to the high level design of near Earth space communication networks that support robotic and human activities in the Earth vicinity through a set of relay communication satellites and their supporting ground stations. The decisions available to the network architect (both technical and contractual) are presented and along with their couplings. The tool is validated by comparing it to NASA's Space Network. The current operations of the system are analyzed and used as the baseline case for the validation process. Results demonstrate that the both performance model and spacecraft design algorithm are accurate to less than 10%, while the cost module produces estimates with a 15% error. Finally, the utility of the tool is demonstrated through three case studies on the evolution of the Space Network. In particular, the impact of new radio-frequency and optical technology to increase the system capacity is analyzed based on the predicted demand for the 2020-2030 decade. Similarly, the savings of flying relay transponders in commercial satellites as hosted payloads are quantified and benchmarked with respect to NASA's current approach of procuring and operating the entire network. Lastly, the tool is used to compare the current Space Network bent-pipe architecture with a constellation of satellites that takes advantage of inter-satellite links to provide full coverage of low Earth orbits with only one ground station.by Marc Sanchez Net.S.M

Support of latency-sensitive space exploration applications in future space communication systems

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 283-300).Latency, understood as the total time it takes for data acquired by a remote platform (e.g. satellite, rover, astronaut) to be delivered to the final user in an actionable format, is a primary requirement for several near Earth and deep space exploration activities. Some applications such as real-time voice and videoconferencing can only be satisfied by providing continuous communications links to the remote platform and enforcing hard latency requirements on the system. In contrast, other space exploration applications set latency requirements because their data's scientific value is dependent on the timeliness with which it is delivered to the final user. These applications, henceforth termed latency-sensitive, are the main focus of this thesis, as they typically require large amounts of data to be returned to Earth in a timely manner. To understand how current space communication systems induce latency, the concept of network centrality is first introduced. It provides a systematic process for quantifying the relative importance of heterogeneous latency contributors, ranking them, and rapidly identifying bottlenecks when parts of the communication infrastructure are modified. Then, a custom-designed centrality measure is integrated within the system architecture synthesis process. It serves as a heuristic function that prioritizes parts of the system for further in-depth analysis and renders the problem of analyzing end-to-end latency requirements manageable. The thesis includes two primary case studies to demonstrate the usefulness of the proposed approach. The first one focuses on return of satellite-based observations for accurate weather forecasting, particularly how latency limits the amount of data available for assimilation at weather prediction centers. On the other hand, the second case study explores how human science operations on the surface of Mars dictate the end-to-end latency requirement that the infrastructure between Mars and Earth has to satisfy. In the first case study, return of satellite observations for weather prediction during the 2020-2030 decade is analyzed based on future weather satellite programs. Recommendations on how to implement their ground segment are also presented as a function of cost, risk and weather prediction spatial resolution. This case study also serves as proof of concept for the proposed centrality measure, as ranking of latency contributors and network implementations can be compared to current and proposed systems such as JPSS' Common Ground Infrastructure and NPOESS' SafetyNet. The second case study focuses on supporting human science exploration activities on the surface of Mars during the 2040's. It includes astronaut activity modeling, quantification of Mars Proximity and Mars-to-Earth link bandwidth requirements, Mars relay sizing and ground infrastructure costing as a function of latency requirements, as well as benchmarking of new technologies such as optical communications over deep space links. Results indicate that levying tight latency requirements on the network that support human exploration activities at Mars is unnecessary to conduct effective science and incurs in significant cost for the Mars Relay Network, especially when no optical technology is present in the system. When optical communications are indeed present, mass savings for the relay system are also possible, albeit trading latency vs. infrastructure costs is less effective and highly dependent on the performance of the deep space optical link.by Marc Sanchez Net.Ph. D

Assessing the impact of real-time communication services on the space network ground segment

Communication networks to support space missions were originally architected around non-real time data services. In fact, missions have always required real-time services (e.g. telemetry and command), but the bulk of scientific data being returned to Earth has typically been highly delay tolerant. Nevertheless, future robotic and human exploration activities are rapidly pushing towards low latency, high data rate services. Examples can be found both in the near Earth domain (e.g. near real-imagery through NASAs LANCE program) and the deep space domain (e.g. HD video from Mars). Therefore, the goal of this paper is to quantify the effect of new real-time high data rate communication requirements on the ground segment of current communication networks. To that end, we start by analyzing operational schedules for NASAs Space Network (SN) in order to characterize the utilization of the overall network in terms of total data volume and contact time, as well as identify current mission drivers. These results are compared against proposed network requirements for future robotic and human near Earth exploration activities in order to quantitatively assess gaps in the SN capabilities. Using these results, we implement a rule-based expert system that translates SN-specific operational contacts into high-level data requirements for the ground segment of the network. We then exercise the expert system in order to derive the requirements that future exploration activities will impose on the SN. Finally quantify the impact of real-time data delivery services across NASAs ground segment by computing the wide-area network cost for different levels of data timeliness

Architecting Space Communication Networks under Mission Demand Uncertainty

Abstract-NASAs Space Network has been a successful program that has provided reliable communication and navigation services for three decades. As the third generation of satellites is being launched, alternatives to the current architecture of the system are being studied in order to improve the performance of the system, reduce its costs and facilitate its integration with the Near Earth Network and the Deep Space Network. Within this context, past research has proven the feasibility of efficiently exploring a large space of alternative network architectures using a tradespace search framework. Architecting a space communication network is a complex task that requires consideration of uncertainty, namely (1) factoring in customer demand variability, (2) predicting technology improvements and (3) considering possible budgetary constraints. This paper focuses on adding uncertainty associated with (1) to the existing communications network architecture tool by describing a heuristic-based model to derive mission concept of operations (conops) as a function of communication requirements. The accuracy of the model is assessed by comparing real conops from current TDRSS-supported missions with the predicted concept of operations. The model is used to analyze how customer forecast uncertainty affects the choice of the future network architecture. In particular, three customer scenarios are generated (low, medium and high load) and compared with the current TDRSS capabilities