SpaceWire Network Research Articles

SpaceART SpaceWire Sniffer for Link Monitoring: A Complete Communication Analysis in a Time-Constrained Test Scenario.

The on-board communication standard adopted in current generation space missions of the European Space Agency, and many other agencies as well, is SpaceWire (SpW). In a SpW network, data are exchanged as well-formed packets, whose structure offers low packet overhead and allows developers to tailor their implementation for SpW applications. The development of SpW-compliant devices requires a specific set of test instruments, namely Electrical Ground Support Equipment (EGSE), to verify the correct functionality of SpW units under test. An example of a SpW EGSE is the SpaceART EGSE Emulator, an EGSE for generation and processing of SpW packets for a time-constrained use-case scenario. This EGSE has been developed to address a mission-related SpW communication between a device and an Instrument Control Unit (ICU). It has allowed the generation and processing of specific SpW packets, which cannot be provided by the mostly used general-purpose SpW EGSEs. In this scope, the SpaceART SpW Sniffer, a SpW link analyser for unobtrusive monitoring of SpW link, has been employed to run a comprehensive set of tests and provide further information on the considered scenario. The SpaceART EGSE Emulator-ICU communication has been thoroughly tested through the SpaceART SpW Sniffer, unobtrusively analysing the exchanged data and allowing to assess the compliance with the defined time constraints from an external point of view. The use of the Sniffer has been crucial for testing the on-board communication, providing important support for the success of the mission employing the tested ICU.

АППАРАТНО-ПРОГРАММНАЯ ОТРАБОТКА КОММУНИКАЦИОННЫХ ПРОТОКОЛОВ ДЛЯ БОРТОВЫХ СЕТЕЙ

The article deals with the problem of hardware-software research of communication protocols for on-board networks. A system is presented that allows testing the developed SpaceWire and SpaceFibre network equipment. Determination of the main stages of development of the system under consideration for SpaceWire technology demonstrates various network structures that meet the stated requirements for hardware and software testing of network equipment and determines the necessary devices for implementing the theory in practice. One of the sections of the article demonstrates the successful implementation of the proposed theory in practice. The described problems of implementing such a research complex for SpaceFibre technology help to determine the vector of further research.

Development of a methodology for testing SpaceWire network switches

Development of a methodology for testing SpaceWire network switches

Design of the readout electronics for the fast trigger and time of flight of the GAMMA-400 gamma-ray telescope

The GAMMA-400 gamma-ray telescope is planned for the launch at the end of this decade on the Navigator service platform designed by Lavochkin Association on an elliptical orbit with following initial parameters: an apogee ~300000, a perigee ~500 km, a rotation period ~7 days and inclination of 51.4°. The apparatus is expected to operate more than 5 years, reaching an unprecedented sensitivity for the search of dark matter signatures and the study of the unresolved and so far unidentified gamma-ray sources. An electronics system, which consists of 14 front-end multichannel electronics modules and the main processing unit with a total power consumption of about 400 W (74W for main processing unit), has been developed for providing fast trigger and veto for the data taking to the experiment. The communication between front-end modules, main processing unit and scientific data acquisition system of the gamma-ray telescope is performed via high-speed SPACEWIRE network. To assure the long-term reliability in space environment, a series of critical issues such as the radiation hardness, thermal design, components and board level quality control, warm and cold redundancy are taken into consideration. The main design concepts for the system, measurements setups together with some test results are presented.

Обеспечение гарантии доставки информации в бор товой сети космического аппар ата на основе интерфейса SpaceWire

Nowadays SpaceWire is regarded as a perspective aerospace data transmission interface standard. This paper gives an analysis of a guaranteed information delivery of SpaceWire networks. The result of the analysis showed key problems that did not allow using this standard in real-time networks. A method was developed and proposed to guarantee the information delivery in the SpaceWire network based on scheduled routing. Tests using a software model of the modified network were performed. The results obtained confirmed the efficiency of the method used to ensure the guarantee of information delivery in the network. It is shown that a network with a modified protocol stack meets real-time requirements.

Method of scheduling channel resources for onboard SpaceWire networks with TDMA

The article presents a new method for scheduling channel resources in SpaceWire onboard networks with support for TDMA technology. The network features based on the SpaceWire network standard and the STP-ISS transport protocol, which provides TDMA technology in the form of the «Scheduling» mechanism, were considered. This mechanism is used in networks with the goal of providing determinism, resolving conflicts and blocks when two or more devices are simultaneously trying to transmit data, occupying a limited channel resource. A comparative analysis of existing methods and algorithms for scheduling channel resources to design a schedule table was conducted. A new method of scheduling channel resources in SpaceWire onboard networks was presented and substantiated. A performance evaluation was carried out using the parameters significant for the space industry. It demonstrates the effectiveness of the developed method.

Applying Active Diagnosis to Space Systems by On-Board Control Procedures

The instrumentation of real systems is often designed for control purposes and control inputs are designed to achieve nominal control objectives. Hence, the available measurements may not be sufficient to isolate faults with certainty and diagnoses are ambiguous. Active diagnosis formulates a planning problem to generate a sequence of actions that, applied to the system, enforces diagnosability and allows to iteratively refine ambiguous diagnoses. This paper analyzes the requirements for applying active diagnosis to space systems and proposes ActHyDiag as an effective framework to solve this problem. It presents the results of applying ActHyDiag to a real-space case study and of implementing the generated plans in the form of on-board control procedures. The case study is a redundant SpaceWire network where up to six instruments, monitored and controlled by the on-board software hosted in the satellite management unit, are transferring science data to a mass memory unit through SpaceWire routers. Experiments have been conducted on a real physical benchmark developed by Thales Alenia Space and demonstrate the effectiveness of the plans proposed by ActHyDiag.

Time assignment system and its performance aboard the Hitomi satellite

Fast timing capability in X-ray observation of astrophysical objects is one of the key properties for the ASTRO-H (Hitomi) mission. Absolute timing accuracies of 350 micro second or 35 micro second are required to achieve nominal scientific goals or to study fast variabilities of specific sources. The satellite carries a GPS receiver to obtain accurate time information, which is distributed from the central onboard computer through the large and complex SpaceWire network. The details on the time system on the hardware and software design are described. In the distribution of the time information, the propagation delays and jitters affect the timing accuracy. Six other items identified within the timing system will also contribute to absolute time error. These error items have been measured and checked on ground to ensure the time error budgets meet the mission requirements. The overall timing performance in combination with hardware performance, software algorithm, and the orbital determination accuracies, etc, under nominal conditions satisfies the mission requirements of 35 micro second. This work demonstrates key points for space-use instruments in hardware and software designs and calibration measurements for fine timing accuracy on the order of microseconds for mid-sized satellites using the SpaceWire (IEEE1355) network.

OMNeT++을 이용한 스페이스와이어 네트워크의 타임코드 전송 지연 분석

SpaceWire is a standard for high-speed links and networks between spacecraft components, which was invented for better, cheaper and faster on-board data handling in spacecraft. The standard defines timecode and its distribution which can be used for time synchronization among the nodes in a SpaceWire network. A timecode output from the time master which provides standard time over a SpaceWire network travels through links and routers to reach every nodes. While traveling, a timecode suffers from transmission delay and jitter which cause some difference in time synchronization among nodes. In this work, a simulator was developed using OMNeT++ to simulate the operation of a SpaceWire network and some analyses were performed on the transmission delay and jitter accompanied with a transmission of a timecode. The result will be used in the near future for the research of a precise time synchronization technique over a SpaceWire network.

STP-ISS Transport Protocol for SpaceWire On-Board Networks

The paper describes the development of a new transport protocol for the SpaceWire onboard networks. It starts from the overview and analysis of existing SpaceWire-oriented transport protocols. Then the paper considers the general industrial requirements for the Transport protocol, which should operate over the SpaceWire network technology. The main two chapters of the paper present the first and the second revisions of the new STP-ISS transport protocol, which has been developed in accordance with the results of the overview and technical requirements. In addition, the authors describe STP-ISS modeling process, which was very efficient for the STP ISS protocol development, testing, analysis and improvement.

Using Network Calculus to compute end-to-end delays in SpaceWire networks

The SpaceWire network standard is promoted by the ESA and is scheduled to be used as the sole on-board network for future satellites. This network uses a wormhole routing mechanism that can lead to packet blocking in routers and consequently to variable end-to-end delays. As the network will be shared by real-time and non real-time traffic, network designers require a tool to check that temporal constraints are verified for all the critical messages. Network Calculus can be used for evaluating worst-case end-to-end delays. However, we first have to model SpaceWire components through the definition of service curves. In this paper, we propose a new Network Calculus element that we call the Wormhole Section. This element allows us to better model a wormhole network than the usual multiplexer and demultiplexer elements used in the context of usual Store-and-Forward networks.

Worst-case end-to-end delays evaluation for SpaceWire networks

SpaceWire is a standard for on-board satellite networks chosen by the ESA as the basis for multiplexing payload and control traffic on future data-handling architectures. However, network designers need tools to ensure that the network is able to deliver critical messages on time. Current research fails to address this needs for SpaceWire networks. On one hand, many papers only seek to determine probabilistic results for end-to-end delays on Wormhole networks like SpaceWire. This does not provide sufficient guarantee for critical traffic. On the other hand, a few papers give methods to determine maximum latencies on wormhole networks that, unlike SpaceWire, have dedicated real-time mechanisms built-in. Thus, in this paper, we propose an appropriate method to compute an upper-bound on the worst-case end-to-end delay of a packet in a SpaceWire network.

Measuring Parameters of SpaceWire Network

SpaceWire is used for on-board satellite networks. It is proposed by the ESA as the basis for future data-handing architectures. It takes an indispensable role for the shortage of bandwidth of bus among data processing. Based on the research of SpaceWire Network, some parameters, such as delay, bit error ratio, bandwidth and throughput, a new scheme of the testing about the parameters of SpaceWire was proposed. Then its implementation technology was analyzed and explained.

스페이스와이어 링크의 시각 동기 성능 개선

This paper deals with the time synchronization problem over SpaceWire links. SpaceWire is a standard for high-speed links and networks between spacecraft components, which was invented for better, cheaper, faster on-board data handling in spacecraft. The standard defines Time-Code for time distribution over SpaceWire network. When a Time-Code is transmitted, transmission delay and jitter is unavoidable. In this paper, a mechanism to remove Time-Code transmission delay and jitter over SpaceWire links is proposed and implemented with FPGA for validation. The proposed mechanism achieves high resolution clock synchronization over SpaceWire links, complies with the standard and can be easily adopted over SpaceWire network.

Fiber-Optic Transceiver Module for High-Speed Intrasatellite Networks

High-speed intrasatellite networks are needed to interconnect units such as synthetic aperture radars, high-resolution cameras, and fast image-compression processors that produce data beyond gigabits per second. We have developed a fiber-optic link, named SpaceFibre, which operates up to 3.125 Gb/s and is compatible with the existing SpaceWire network. The link provides symmetrical, bidirectional, full-duplex, and point-to-point communication. It employs 850-nm vertical-cavity surface emitting lasers, radiation-hardened laser-optimized 50/125 mum graded-index fibers, and GaAs p-i-n photo diodes. The transceiver electronics is realized using a multilayer-ceramic-substrate technology that enables the passive alignment of optical fibers to active devices. The SpaceFibre link demonstrator was tested to transfer data at 2.5 Gb/s over 100 m with a bit error rate of less than 1.3middot10-14. Fiber-pigtailed modules were stressed with temperature variations from -40degC to +85degC, vibrations up to 30 g, and mechanical shocks up to 3900 g. The test results of 20 modules show that the SpaceFibre link is a promising candidate for the upcoming high-speed intrasatellite networks

SpaceWire: a satellite on‐board data‐handling network

SpaceWire is a network designed for handling payload data and control information on‐board a spacecraft. It provides a unified, high‐speed, data‐handling infrastructure for connecting together sensors (e.g. optical or radar instruments), processing elements (e.g. digital signal processors), mass‐memory units, downlink telemetry sub‐systems and ground support equipment (GSE). SpaceWire is intended to meet the needs of future, high‐capability space missions. It supports equipment compatibility and re‐use at both the component and sub‐system levels. This paper first considers the key factors that drove the specification of SpaceWire, explaining the particular demands imposed by the space environment. The components of a SpaceWire network are then introduced. The key features of SpaceWire are summarised and the support that SpaceWire provides for fault tolerance is described. Finally a summary is given of the current status of the SpaceWire standard and its application in space missions.