1、 Standard AIAA S-133-6-2013 S-102.2.5-2009 Space Plug-and-Play Architecture Standard System Timing AIAA standards are copyrighted by the American Institute of Aeronautics and Astronautics (AIAA), 1801 Alexander Bell Drive, Reston, VA 20191-4344 USA. All rights reserved. AIAA grants you a license as
2、follows: The right to download an electronic file of this AIAA standard for storage on one computer for purposes of viewing, and/or printing one copy of the AIAA standard for individual use. Neither the electronic file nor the hard copy print may be reproduced in any way. In addition, the electronic
3、 file may not be distributed elsewhere over computer networks or otherwise. The hard copy print may only be distributed to other employees for their internal use within your organization. AIAA S-133-6-2013 Space Plug-and-Play Architecture Standard System Timing Sponsored by American Institute of Aer
4、onautics and Astronautics Approved August 2013 Abstract This document details how common time is provided for Space Plug-and-Play Architecture systems. Timing synchronization is accomplished through the use of time-at-tone messages and synchronization pulses. AIAA S-133-6-2013 ii Published by Americ
5、an Institute of Aeronautics and Astronautics 1801 Alexander Bell Drive, Reston, VA 20191 Copyright 2013 American Institute of Aeronautics and Astronautics All rights reserved No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior writ
6、ten permission of the publisher. Printed in the United States of America ISBN 978-1-62410-234-9 AIAA S-133-6-2013 iii Contents Foreword iv 1 Scope . 1 2 Tailoring . 1 3 Applicable Documents . 1 4 Vocabulary . 1 4.1 Acronyms and Abbreviated Terms . 1 4.2 Terms and Definitions 2 5 SPA System Timing .
7、2 5.1 Pulse-per-Second (PPS) Synchronization . 2 5.2 Time-at-Tone (TAT) Message 2 5.3 TAT and PPS Sources . 3 5.4 Time Source Priority . 3 5.5 System Time Availability 4 5.6 Time Latency 4 5.7 PPS Jitter . 4 5.8 PPS Clock Bias 4 Annex A Time Discontinuities (Informative) . 5 A.1 Overview 5 A.2 Refer
8、ence Design: PnPSat-1 5 Annex B PPS Routers (Informative) . 6 B.1 Overview 6 B.2 Reference Design: PnPSat-1 6 Annex C Master Clock Source Selection (Informative) 7 C.1 Overview 7 C.2 Reference Design: PnPSat-1 7 AIAA S-133-6-2013 iv Foreword This standard was developed through a partnership of the A
9、ir Force Research Laboratory Space Vehicles Directorate, the Air Force Office of Operationally Responsive Space, numerous government contractor teams, independent contractor teams, and academic experts. The System Timing standard is one piece of the Space Plug-and-Play Architecture (SPA) which is a
10、system that aims to reduce the cost and timeline of getting spacecraft into operational use. SPA incorporates the use of design tools, standard interfaces for hardware and software, and standard, modular structures and wiring. The system timing methods described herein provide for common time within
11、 the system, allowing for synchronization of processes and functions across the system. This document describes how common time is provided to components in SPA systems using a time-at-tone (TAT) message and synchronization pulses. Annexes A and B are informational and provide information on timing
12、disruptions, time source priority, and master clock source considerations, with descriptions of timing implementation within a reference model. This particular volume of the SPA System Timing Standard contains information not recorded in previous documentation. It is part of a set of 10 documents de
13、scribing other components of the standard: SPA Guidebook SPA Networking Standard SPA Logical Interface Standard SPA Physical Interface Standard SPA 28V Power Service Standard SPA Ontology Standard SPA Test Bypass Standard SPA SpaceWire Subnet Adaptation Standard SPA System Capability Guide At the ti
14、me of approval, the members of the AIAA SPA Committee on Standards were: Fred Slane, Chair Space Infrastructure Foundation Jeanette Arrigo Sierra Nevada Corporation Scott Cannon Utah State University Ken Center PnP Innovations Don Fronterhouse* PnP Innovations Rod Green Design Net Engineering Group
15、Jane Hansen HRP Systems Doug Harris The Aerospace Corporation, ORS Office Paul Jaffe U.S. Naval Research Laboratory Stanley Kennedy* Comtech Aero-Astro Ronald Kohl R.J. Kohl therefore the PPS Router must inhibit sending a PPS signal to all users when it is listening for a Master Source. The timing g
16、eneration circuit on PnPSat1 that is active at power up of the satellite. Initially, the mode of the PPS Router (in the Power Hub) is set to “listen“, then when it acquires the PPS signal from the timing generation circuit, its mode is changed such that the pps signal is delivered to all endpoints.
17、If another potential PPS source becomes available that the system is programmed to consider more appropriate (i.e., from a GPS receiver), then a message is sent to the PPS Router to acquire its signal as master. The PPS Router reconfigures to “listen“, captures the more accurate signal, then changes
18、 its mode to deliver the new PPS signal to all endpoints. If the PPS Router senses that the source has dropped out, then its mode changes to listen and it acquires a new PPS source. There is no prioritization of the available sources. While the PPS Router is not delivering a PPS signal, the individu
19、al ASIMs derive a local PPS signal from their own local oscillators. Typically the search for a new PPS source by the PPS Router is less than 10 seconds. 1 American Institute of Aeronautics and Astronautics 1801 Alexander Bell Drive, Suite 500 Reston, VA 20191-4344 www.aiaa.org ISBN 978-1-62410-234-9
