The Global Positioning System: Global Developments and Opportunities

International Relations/Trade,

System control of an autonomous planetary mobile spacecraft

The goal is to suggest the scheduling and control functions necessary for accomplishing mission objectives of a fairly autonomous interplanetary mobile spacecraft, while maximizing reliability. Goals are to provide an extensible, reliable system conservative in its use of on-board resources, while getting full value from subsystem autonomy, and avoiding the lure of ground micromanagement. A functional layout consisting of four basic elements is proposed: GROUND and SYSTEM EXECUTIVE system functions and RESOURCE CONTROL and ACTIVITY MANAGER subsystem functions. The system executive includes six subfunctions: SYSTEM MANAGER, SYSTEM FAULT PROTECTION, PLANNER, SCHEDULE ADAPTER, EVENT MONITOR and RESOURCE MONITOR. The full configuration is needed for autonomous operation on Moon or Mars, whereas a reduced version without the planning, schedule adaption and event monitoring functions could be appropriate for lower-autonomy use on the Moon. An implementation concept is suggested which is conservative in use of system resources and consists of modules combined with a network communications fabric. A language concept termed a scheduling calculus for rapidly performing essential on-board schedule adaption functions is introduced

Deep Space Network information system architecture study

The purpose of this article is to describe an architecture for the Deep Space Network (DSN) information system in the years 2000-2010 and to provide guidelines for its evolution during the 1990s. The study scope is defined to be from the front-end areas at the antennas to the end users (spacecraft teams, principal investigators, archival storage systems, and non-NASA partners). The architectural vision provides guidance for major DSN implementation efforts during the next decade. A strong motivation for the study is an expected dramatic improvement in information-systems technologies, such as the following: computer processing, automation technology (including knowledge-based systems), networking and data transport, software and hardware engineering, and human-interface technology. The proposed Ground Information System has the following major features: unified architecture from the front-end area to the end user; open-systems standards to achieve interoperability; DSN production of level 0 data; delivery of level 0 data from the Deep Space Communications Complex, if desired; dedicated telemetry processors for each receiver; security against unauthorized access and errors; and highly automated monitor and control

Contact Plan Design for GNSS Constellations: A Case Study with Optical Inter-Satellite Links

Optical Inter-Satellite Links (OISLs) are being considered for future Global Navigation Satellite System (GNSS) constellations. Thanks to OISLs, the constellation incorporates improved clock synchronization and precise ranging among the satellites, which are essential features to achieve accurate time and orbit determination. High data rate communications within the space segment also reduce ground segment dependency, by means of decentralized access to information. However, the dual optimization of data and navigation performance metrics requires a careful assignment of OISLs to the available laser communication terminals on-board. To this end, we present a Contact Plan Design (CPD) scheme based on a Degree Constrained Minimum Spanning Tree heuristic applied to such OISL-enabled GNSS (O-GNSS) constellations. Results on the Kepler system, a novel GNSS proposal, show that a fair distribution of connectivity among the constellation can be ensured while optimizing its range-based position estimation capabilities (PDOP). A PDOP improvement of 85 % is reached on average by the optimized contact plan with respect to a generic scheduler that disregards the geometrical distribution of the chosen links

Trusted GNSS-Based Time Synchronization for Industry 4.0 Applications

The protection of satellite-derived timing information is becoming a fundamental requirement in Industry 4.0 applications, as well as in a growing number of critical infrastructures. All the industrial systems where several nodes or devices communicate and/or coordinate their functionalities by means of a communication network need accurate, reliable and trusted time synchronization. For instance, the correct operation of automation and control systems, measurement and automatic test systems, power generation, transmission, and distribution typically require a sub-microsecond time accuracy. This paper analyses the main attack vectors and stresses the need for software integrity control at network nodes of Industry 4.0 applications to complement existing security solutions that focus on Global Navigation Satellite System (GNSS) radio-frequency spectrum and Precision Time Protocol (PTP), also known as IEEE-1588. A real implementation of a Software Integrity Architecture in accordance with Trusted Computing principles concludes the work, together with the presentation of promising results obtained with a flexible and reconfigurable testbed for hands-on activities

PintaOnWeb - The Front End of GSOC’s Next Generation Mission Planning Systems

PintaOnWeb is the next-generation user interface of the generic mission planning tool suite at GSOC. It is a web-based application, which is mostly connected to a dedicated planning system based on GSOC’s Reactive Planning framework, where PintaOnWeb takes its part as an "inspection window" into the planning system. Moreover, PintaOnWeb allows for modifications of the planning model, so that the automated planning can be complemented by manual modifications if needed. As a consequence, PintaOnWeb can be used for fully automated planning as well as fully manual planning, or anything in-between. Since it runs independently of the core planning system, we can easily deploy multiple instances with different configurations or to different locations, such as to a cloud environment that allows it to scale based on the demands of the users. The approach of developing a web-application required several design and architectural decisions and is performed in an agile development process based on evolving requirements. Both topics are described in the paper at hand, besides giving a detailed insight into the new tool, outlining the chosen technologies and available features. PintaOnWeb is already part of the fully automated planning system for the Earth observation mission EnMAP which launched in April 2022. Here, PintaOnWeb both helps the planners to get visual feedback for any implemented change, and serves as a display of the planning system to operators of other subsystems. Furthermore, it forms the basis of GSOC’s novel "Integrated Terminal and Antenna Scheduling" application. One of the possible future applications is the planning and scheduling of satellite constellations, such as for the next generation of the global navigation satellite system Galileo

Space exploration: The interstellar goal and Titan demonstration

Automated interstellar space exploration is reviewed. The Titan demonstration mission is discussed. Remote sensing and automated modeling are considered. Nuclear electric propulsion, main orbiting spacecraft, lander/rover, subsatellites, atmospheric probes, powered air vehicles, and a surface science network comprise mission component concepts. Machine, intelligence in space exploration is discussed

PINTA - one Tool to plan them all

In the recent years, the “Program for INteractive Timeline Analysis” PINTA, developed at the German Space Operation Center (GSOC), was continuously improved and experienced several evolution steps. PINTA is a GUI application running on Windows-based computer systems, whose main purpose is to serve as the anchor tool for a mission planning operation’s engineer when generating, modifying or analysing a mission timeline. This is supported by calling automatic planning algorithms of the embedded generic planning library “PLAnningTOol” PLATO, using input of the embedded orbit propagation and event calculation library “SpaceCraft Orbit and GroundTrack Analysis Tool” SCOTA, or its expandability through plugins. PINTA is the generic basis of many semi-automated mission planning systems for past, current and future spacecraft projects operated at GSOC. It is used or has been used for the missions Grace, TET-OOV, FireBird, Grace-FollowOn, Eu:CROPIS and is currently prepared for CubeL. Furthermore, PINTA serves as the timeline analysis tool for validating the TerraSAR-X/TanDEM-X mission planning system. The variety of use cases was further extended to support Launch and Early Orbit Phases (LEOPs) in its special “SoEEditor” configuration as the new generic editing tool for the so-called “Sequence of Events”. It was successfully used for the satellites Biros, HAG-1, PAZ, Grace-FollowOn 1 & Grace-FollowOn 2, Eu:Cropis, EDRS-C and is currently in preparation for EnMAP. In addition to LEOP’s, the SoEEditor was also capable of supporting the constellation maneuvers for the TerraSAR-X/TanDEM-X mission. Besides all these use cases, the paper at hand will especially describe how PINTA was even further extended to not only tackle spacecraft-based but also ground-based scheduling. On the one hand it serves as an “On-Call Tool” to support the on-call shifts by automatically generating conflict-free role-based shift plans for all subsystems by considering various constraints like person outages, working hours, role-conflicts, etc… The plan can then be further adapted manually to cope with user change-requests. On the other hand it is used as a “Multi-Mission-Control-Room-and-pass-Scheduler” (MuMiCoRoS) to coordinate the ground-station booking of all LEO (low-earth orbit) satellites: TerraSAR-X, TanDEM-X, TET, Biros, Grace-FollowOn 1 & 2 and Eu:CROPIS. In order to avoid ground-station and operator conflicts between the missions, an automatic and combined plan for all satellites is generated which can then be further modified manually if necessary. As another use case, PINTA (a.k.a. GPT; Galileo Planning Tool) supports the Galileo Service Operation (GSOp). The planning process involves three timelines: a Short-Term Plan (STP), covering the next ten days, two Mid-Term Plans (MTP) for the Operational (OPE) and the Validation (VAL) chain), covering the next 15 weeks, and a Long-Term Plan (LTP), covering the next 15 months. The activities in these timeframes cover all subsystems of Galileo: Flight Ops, Control segment, Mission segment, remote sites, service operations, hardware, software, hosting, network, etc ... In order to support the GSOp, numerous additional features, like importers, exporters, interfaces and plugins had to be added to PINTA

Applying autonomy to distributed satellite systems: Trends, challenges, and future prospects

While monolithic satellite missions still pose significant advantages in terms of accuracy and operations, novel distributed architectures are promising improved flexibility, responsiveness, and adaptability to structural and functional changes. Large satellite swarms, opportunistic satellite networks or heterogeneous constellations hybridizing small-spacecraft nodes with highperformance satellites are becoming feasible and advantageous alternatives requiring the adoption of new operation paradigms that enhance their autonomy. While autonomy is a notion that is gaining acceptance in monolithic satellite missions, it can also be deemed an integral characteristic in Distributed Satellite Systems (DSS). In this context, this paper focuses on the motivations for system-level autonomy in DSS and justifies its need as an enabler of system qualities. Autonomy is also presented as a necessary feature to bring new distributed Earth observation functions (which require coordination and collaboration mechanisms) and to allow for novel structural functions (e.g., opportunistic coalitions, exchange of resources, or in-orbit data services). Mission Planning and Scheduling (MPS) frameworks are then presented as a key component to implement autonomous operations in satellite missions. An exhaustive knowledge classification explores the design aspects of MPS for DSS, and conceptually groups them into: components and organizational paradigms; problem modeling and representation; optimization techniques and metaheuristics; execution and runtime characteristics and the notions of tasks, resources, and constraints. This paper concludes by proposing future strands of work devoted to study the trade-offs of autonomy in large-scale, highly dynamic and heterogeneous networks through frameworks that consider some of the limitations of small spacecraft technologies.Postprint (author's final draft