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A Modeling Pattern for Layered System Interfaces

Communications between systems is often initially represented at a single, high level of abstraction, a link between components. During design evolution it is usually necessary to elaborate the interface model, defining it from several different, related viewpoints and levels of abstraction. This paper presents a pattern to model such multi-layered interface architectures simply and efficiently, in a way that supports expression of technical complexity, interfaces and behavior, and analysis of complexity. Each viewpoint and layer of abstraction has its own properties and behaviors. System elements are logically connected both horizontally along the communication path, and vertically across the different layers of protocols. The performance of upper layers depends on the performance of lower layers, yet the implementation of lower layers is intentionally opaque to upper layers. Upper layers are hidden from lower layers except as sources and sinks of data. The system elements may not be linked directly at each horizontal layer but only via a communication path, and end-to-end communications may depend on intermediate components that are hidden from them, but may need to be shown in certain views and analyzed for certain purposes. This architectural model pattern uses methods described in ISO 42010, Recommended Practice for Architectural Description of Software-intensive Systems and CCSDS 311.0-M-1, Reference Architecture for Space Data Systems (RASDS). A set of useful viewpoints and views are presented, along with the associated modeling representations, stakeholders and concerns. These viewpoints, views, and concerns then inform the modeling pattern. This pattern permits viewing the system from several different perspectives and at different layers of abstraction. An external viewpoint treats the systems of interest as black boxes and focuses on the applications view, another view exposes the details of the connections and other components between the black boxes. An internal view focuses on the implementation within the systems of interest, either showing external interface bindings and specific standards that define the communication stack profile or at the level of internal behavior. Orthogonally, a horizontal view isolates a single layer and a vertical viewpoint shows all layers at a single interface point between the systems of interest. Each of these views can in turn be described from both behavioral and structural viewpoints.

Shames, Peter M.↗

Services, architectures, and protocols for space data systems

The author presents a comprehensive discussion of three major aspects of the work of the Consultative Committee for Space Data Systems (CCSDS), a worldwide cooperative effort of national space agencies. The author examines the CCSDS space data communications network concept on which the data communications facilities of future advanced orbiting systems will be based. He derives the specifications of an open communications architecture as a reference model for the development of services and protocols that support the transfer of information over space data communications networks. Detailed specifications of the communication services and information transfer protocols that have reached a high degree of maturity and stability are offered. The author also includes a complete list of currently available CCSDS standards and supporting documentation.

Helgert, Hermann J.↗

Simulation Modeling and Performance Evaluation of Space Networks

In space exploration missions, the coordinated use of spacecraft as communication relays increases the efficiency of the endeavors. To conduct trade-off studies of the performance and resource usage of different communication protocols and network designs, JPL designed a comprehensive extendable tool, the Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE). The design and development of MACHETE began in 2000 and is constantly evolving. Currently, MACHETE contains Consultative Committee for Space Data Systems (CCSDS) protocol standards such as Proximity-1, Advanced Orbiting Systems (AOS), Packet Telemetry/Telecommand, Space Communications Protocol Specification (SCPS), and the CCSDS File Delivery Protocol (CFDP). MACHETE uses the Aerospace Corporation s Satellite Orbital Analysis Program (SOAP) to generate the orbital geometry information and contact opportunities. Matlab scripts provide the link characteristics. At the core of MACHETE is a discrete event simulator, QualNet. Delay Tolerant Networking (DTN) is an end-to-end architecture providing communication in and/or through highly stressed networking environments. Stressed networking environments include those with intermittent connectivity, large and/or variable delays, and high bit error rates. To provide its services, the DTN protocols reside at the application layer of the constituent internets, forming a store-and-forward overlay network. The key capabilities of the bundling protocols include custody-based reliability, ability to cope with intermittent connectivity, ability to take advantage of scheduled and opportunistic connectivity, and late binding of names to addresses. In this presentation, we report on the addition of MACHETE models needed to support DTN, namely: the Bundle Protocol (BP) model. To illustrate the use of MACHETE with the additional DTN model, we provide an example simulation to benchmark its performance. We demonstrate the use of the DTN protocol and discuss statistics gathered concerning the total time needed to simulate numerous bundle transmissions

network protocols↗

Medical Data Architecture (MDA) Project Status

The Medical Data Architecture (MDA) project supports the Exploration Medical Capability (ExMC) risk to minimize or reduce the risk of adverse health outcomes and decrements in performance due to in-flight medical capabilities on human exploration missions. To mitigate this risk, the ExMC MDA project addresses the technical limitations identified in ExMC Gap Med 07: We do not have the capability to comprehensively process medically-relevant information to support medical operations during exploration missions. This gap identifies that the current in-flight medical data management includes a combination of data collection and distribution methods that are minimally integrated with on-board medical devices and systems. Furthermore, there are a variety of data sources and methods of data collection. For an exploration mission, the seamless management of such data will enable a more medically autonomous crew than the current paradigm. The medical system requirements are being developed in parallel with the exploration mission architecture and vehicle design. ExMC has recognized that in order to make informed decisions about a medical data architecture framework, current methods for medical data management must not only be understood, but an architecture must also be identified that provides the crew with actionable insight to medical conditions. This medical data architecture will provide the necessary functionality to address the challenges of executing a self-contained medical system that approaches crew health care delivery without assistance from ground support. Hence, the products supported by current prototype development will directly inform exploration medical system requirements.In fiscal year 2018, the MDA project developed Test Bed 2, the second iteration in a series of prototypes with functionality focused on data security through role-based access control and encryption, integration with One Portal exercise software and ingestion of an ultrasound Digital Imaging and Communications in Medicine (DICOM) file and image display. Test Bed 2 advances the medical data system architecture framework by providing these functionalities in a scalable system that maintained a layered, modular design. The architecture framework uses a data services approach with role-based access to data in a customized medical record system suitable for space exploration. These functionalities were demonstrated as part of the Next Space Technologies for Exploration Partnerships (NextSTEP) ground test demonstrated at the NASA Johnson Space Center Integrated Power, Avionics and Software (iPAS) facility. Interfacing to a Core Flight Software (CFS) system, the MDA system, using Consultative Committee for Space Data Systems (CCSDS) protocol, transferred an exercise file from the simulated flight MDA system to a mirrored MDA system on the ground through the CFS system. The selection of data sources and demonstrations enabled the team to address stakeholder concerns throughout the development process. In the next iteration, the MDA team will work with stakeholders to identify additional relevant functionalities to further advance system data models, standards and principles that will inform the medical system requirements development.

medical data architecture↗

Asynchronous Message Service Reference Implementation

This software provides a library of middleware functions with a simple application programming interface, enabling implementation of distributed applications in conformance with the CCSDS AMS (Consultative Committee for Space Data Systems Asynchronous Message Service) specification. The AMS service, and its protocols, implement an architectural concept under which the modules of mission systems may be designed as if they were to operate in isolation, each one producing and consuming mission information without explicit awareness of which other modules are currently operating. Communication relationships among such modules are self-configuring; this tends to minimize complexity in the development and operations of modular data systems. A system built on this model is a society of generally autonomous, inter-operating modules that may fluctuate freely over time in response to changing mission objectives, modules functional upgrades, and recovery from individual module failure. The purpose of AMS, then, is to reduce mission cost and risk by providing standard, reusable infrastructure for the exchange of information among data system modules in a manner that is simple to use, highly automated, flexible, robust, scalable, and efficient. The implementation is designed to spawn multiple threads of AMS functionality under the control of an AMS application program. These threads enable all members of an AMS-based, distributed application to discover one another in real time, subscribe to messages on specific topics, and to publish messages on specific topics. The query/reply (client/server) communication model is also supported. Message exchange is optionally subject to encryption (to support confidentiality) and authorization. Fault tolerance measures in the discovery protocol minimize the likelihood of overall application failure due to any single operational error anywhere in the system. The multi-threaded design simplifies processing while enabling application nodes to operate at high speeds; linked lists protected by mutex semaphores and condition variables are used for efficient, inter-thread communication. Applications may use a variety of transport protocols underlying AMS itself, including TCP (Transmission Control Protocol), UDP (User Datagram Protocol), and message queues.

Burleigh, Scott C.↗

The Deep Impact Network Experiment Operations Center

Delay/Disruption Tolerant Networking (DTN) promises solutions in solving space communications challenges arising from disconnections as orbiters lose line-of-sight with landers, long propagation delays over interplanetary links, and other phenomena. DTN has been identified as the basis for the future NASA space communications network backbone, and international standardization is progressing through both the Consultative Committee for Space Data Systems (CCSDS) and the Internet Engineering Task Force (IETF). JPL has developed an implementation of the DTN architecture, called the Interplanetary Overlay Network (ION). ION is specifically implemented for space use, including design for use in a real-time operating system environment and high processing efficiency. In order to raise the Technology Readiness Level of ION, the first deep space flight demonstration of DTN is underway, using the Deep Impact (DI) spacecraft. Called the Deep Impact Network (DINET), operations are planned for Fall 2008. An essential component of the DINET project is the Experiment Operations Center (EOC), which will generate and receive the test communications traffic as well as "out-of-DTN band" command and control of the DTN experiment, store DTN flight test information in a database, provide display systems for monitoring DTN operations status and statistics (e.g., bundle throughput), and support query and analyses of the data collected. This paper describes the DINET EOC and its value in the DTN flight experiment and potential for further DTN testing.

flight experiment↗

Standardization activity for the spacecraft onboard interfaces

The Consultative Committee for Space Data Systems (CCSDS) is an international organization of national space agencies that is organized to promote theinterchange of space related information. CCSDS is branching out to provide new standards to enhanced reuse of spacecraft equipment and software onboard of a spacecraft. This effort is know as Spacecraft Onboard Interface (SOIF). SOIF expects that these standards will be well used within the space community, and that they will be based on the well-known Internet protocols. This paper will provide a description of the SOIF work by reviewing this work with three orthogonal views. The Services View describes the data communications services that are provided to the users. The Interoperability view provides a description to users on how to use SOIF to interchange between different spacecraft data busses. And finally, the Protocol view, describes the protocols and services that are to be implemented in order to provide the users with the advantages of the SOIF architecture. This paper will give the reader an excellent introduction to the work of the international SOIF team.

Spacecraft interfaces standard interfaces CCSDS↗

The spacecraft onboard interface standardization activity

The Consultative Committee for Space Data Systems (CCSDS) is an international organization of national space agencies (such as NASA in the United States) that is organized to promote the interchange of space related information. Now, CCSDS is branching out to provide new standards for the interchange of information, and the interconnection of subsystems and devices onboard of a spacecraft. This effort is know as Spacecraft Onboard Interface (SOIF). SOIF will publish standards that will allow for the enhanced reuse of spacecraft equipment and software. SOIF expects that these standards will be well known and used within the space community, and that they will be based on or similar to the well-known Internet protocols. This paper will provide a description of the SOIF work by reviewing this work with three orthogonal views. The first of these views is the Protocol view, which describes the protocols and services that are to be implemented in order to provide the users with the advantages of the SOIF architecture. The second of these views is the Services View, which describes the data communications services that are provided to the users. And finally, the Interoperability view provides a description to users how SOIF can be used to interchange between different spacecraft data busses. This paper will give the reader an excellent introduction to the work of the international SOIF team.

spacecraft interfaces standard interfaces CCSDS↗

The spacecraft onboard interface standardization activity

The Consultative Committee for Space Data Systems (CCSDS) is an international organization of national space agencies (such as NASA in the United States) that is organized to promote the interchange of space related information. Now, CCSDS is branching out to provide new standards for the interchange of information, and the interconnection of subsystems and devices onboard of a spacecraft. This effort is know as Spacecraft Onboard Interface (SOIF). SOIF will publish standards that will allow for the enhanced reuse of spacecraft equipment and software. SOIF expects that these standards will be well known and used within the space community, and that they will be based on or similar to the well-known Internet protocols. This paper will provide a description of the SOIF work by reviewing this work with three orthogonal views. The first of these views is the Protocol view, which describes the protocols and services that are to be implemented in order to provide the users with the advantages of the SOIF architecture. The second of these views is the Services View, which describes the data communications services that are provided to the users. And finally, the Interoperability view provides a description to users how SOIF can be used to interchange between different spacecraft data busses. This paper will give the reader an excellent introduction to the work of the international SOIF team.

spacecraft interfaces standard interfaces CCSDS↗