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GJB 1198 consists of the following eight parts under the general title Telemetry tracking command and data handling for spacecraft:
——Part 1: PCM telecommand;
——Part 2: PCM telemetry;
——Part 3: Telemetry channel coding;
——Part 4: Ranging;
——Part 5: Radio frequency and modulation;
——Part 6: Packet telemetry;
——Part 7: Packet telecommand;
——Part 8: Onboard data handling interface.
This part is Part 8 of GJB 1198.
This part replaces GJB 1198.8-1991 Telemetry tracking command and data handling for satellite: Onboard data handling interface.
Clauses 1 to 6 of this part are prepared with reference to Part II of the European Space Agency standard TTC-B-01 Space Craft Data Handling Interface Standards (1979), and the technical indexes are classified into two levels: A and B, of which Level B index is lower; the two switch commands of the previous standard are combined into one; the number transmitted by serial input and output channels is longer and more flexible; Clause 1 "General" and Clause 3 "Data bus interface standard" of this standard are not adopted. The data bus interface, i.e., Clause 7 of this part is prepared according to GJB 289A-1997 Digital time division command/response multiplex data bus, which is identical to the US military standard MIL-STD-1553B Aircraft Internal Time Division Command/Response Multiplex Data Bus (1980); all these differences are based on the actual situation of spacecraft development in China.
The following main changes have been made in this part with respect to the previous edition:
a) "Serial 8Nbit digital channel" and "8Nbit serial loading command" only limit N to be a positive integer to meet the requirements of spacecraft for digital quantity transmission;
b) The contents of serial data bus interface are added, and the relevant contents of GJB 289A-1997 Digital time division command/response multiplex data bus are adopted; besides GJB 289A-1997, the content of simplified serial data bus is added.
This part was proposed by China Aerospace Science and Technology Corporation.
This part is under the jurisdiction of China Aerospace Standardization Institute.
This part was firstly issued in April 1991, and firstly revised this time.
Telemetry tracking command and data handling for spacecraft
Part 8: Onboard data handling interface
1 Scope
This part specifies the general provisions of interface of spacecraft data handling system (hereinafter referred to as data handling system), as well as telemetry channel interface, telecommand channel interface and serial data bus interface.
This part is applicable to spacecraft data handling system and users who have interface with data handling system.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this part. However, parties to agreements based on this part are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest editions apply to this part.
GJB 289A-1997 Digital time division command/response multiplex data bus
GJB 727A-1998 Terms and acronyms of space tracking telemetry and command system
3 Terms and definitions
For the purposes of this part, the terms and definitions established in GJB 727A-1998 and the following ones apply.
3.1
central terminal unit (CTU)
central control equipment of data handling system, which collects data acquired from remote unit, data transmitted through serial data bus and data generated by computer software; processes, stores and sends downlink telemetry data to telemetry transmitter (transponder) of spacecraft; processes, stores and distributes telecommands and data from earth station or other spacecraft, as well as control commands and data generated by spacecraft; generates spacecraft clock, implements the handling of spacecraft computer, and realizes the handling of serial data bus and spacecraft data.
3.2
remote terminal unit (RTU)
equipment configured at different parts of spacecraft to collect telemetry data and distribute commands and data, which can also complete closed-loop autonomous control
3.3
remote bus interface (RBI)
serial data bus interface boards configured in other subsystems, equipment and scientific instruments which are used to realize data exchange between CTU and these subsystems, equipment and scientific instruments via serial data bus
3.4
telecommand unit (TCU)
equipment for receiving uplink telecommand information (including data and commands) from spacecraft telecommand receiver (transponder). These messages are processed to generate direct ON/OFF command for users or sent to CTU in the form of serial loading commands.
3.5
command decoder unit (CDU)
equipment for decoding uplink telecommand information to generate direct ON/OFF command
3.6
direct ON/OFF command
ON/OFF command transmitted to the spacecraft in the form of command through the earth station or other spacecraft, and directly decoded by TCU and CDU
3.7
routed ON/OFF command
ON/OFF command transmitted to the spacecraft in the form of data injection through the earth station or other spacecraft, and output by RTU after being processed by CTU, which can be output in real time or with delay
3.8
on-board ON/OFF command
command generated by spacecraft according to pre-given algorithms and criteria during spacecraft operation
4 General provisions
4.1 General
Onboard data handling interface shall ensure electrical matching and fault isolation between interfaces.
4.2 Types of interfaces
4.2.1 Telemetry channel is the interface for collecting user data by data handling system. Because of the different types of data collected, the telemetry channel can adopt single or several transmission lines. It is also classified into the following categories:
a) Analog channel: for collecting analog signals input by single or double ends;
b) Digital channel: for collecting 8Nbit serial digital signal (N is a positive integer);
c) Bi-level digital channel: for collecting 1-bit status data, and compile 8-bit status data into a group (one telemetry word);
d) Timing channel: for acquiring the time when a single event occurs.
4.2.2 The telecommand channel is the interface for transmitting the commands and data of the data handling system to the user. Because of the different types of commands, the telecommand channel can also adopt one or more transmission lines. It is classified into the following categories:
a) ON/OFF command channel: it is provided to users in the form of pulses with a certain width, which is used to drive loads with higher power;
b) Serial loading command channel: for transmitting 8Nbit data words to users (N is a positive integer).
4.2.3 The serial data bus is used to realize the information transmission among modules of the data handling system and between the data handling system and spacecraft subsystems, equipment and scientific instruments through the remote bus interface. PCM data is transmitted based on the principle of time division multiplexing.
4.3 Agreement of signal and level
4.3.1 Serial digital signal (NRZ-L)
This kind of signal appears in telemetry digital channel interface, and command channel interface loaded with telecommand serial. For telemetry channel, serial digital signal is the input of data handling system; while for telecommand channel, serial digital signal (data word) is the output of data handling system. The logic "1" of digital signal is represented by positive voltage or switch OFF, and the logic "0" of digital signal is represented by zero voltage or switch ON.
4.3.2 Sampling signal and address signal
This kind of signal is used for the transmission of serial digital signals. When the number of user addresses in specific subsystem of spacecraft is small, the sampling signal is the gated signal directly provided by the RTU to the user; when the number of user addresses in a specific subsystem is large (generally more than 8), address codes may be provided to users in the form of address signals, and then the subsystem completes address decoding by itself to generate gated signals of corresponding addresses.
The gated signal, whether directly provided by the sampling signal or generated by decoding the address signal, is a switch closing signal. In the working state (i.e. gated state), the switch is ON; in the non working state, the switch is OFF. When the circuit is designed to ensure the working state, the user input end is at zero level.
4.3.3 Bi-level digital signal
Bi-level digital signals have no non-working state, i.e. "static state".
This kind of signal is the data input of telemetry bi-level digital channel. Represented by two logic states, positive voltage corresponds to logic “1” and zero voltage corresponds to logic “0”.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General provisions
5 Telemetry channel interface
6 Telecommand channel interface
7 Serial data bus interface (recommendatory)
航天器测控和数据管理
第8部分：数据管理接口
1 范围
本部分规定了航天器数据管理系统(以下简称数管系统)接口的总则以及遥测通道接口、遥控通道接口和串行数据总线接口。
本部分适用于航天器数管系统以及与数管系统接口的用户。
2 规范性引用文件
下列文件中的条款通过本部分的引用而成为本部分的条款。凡是注日期的引用文件，其随后所有的修改单(不包含勘误的内容)或修订版均不适用于本部分，然而，鼓励根据本部分达成协议的各方研究是否可使用这些文件的最新版本。凡是不注日期的引用文件，其最新版本适用于本部分。
GJB 289A-1997 数字式时分制指令/响应型多路传输数据总线
GJB 727A-1998 航天测控系统术语与缩略语
3 术语和定义
GJB 727A-1998 确立的以及下列术语和定义适用于本部分。
3.1
中央单元(CTU) central terminal unit
数管系统的中央控制设备，它汇集来自远置单元的采集数据、经串行数据总线传送来的数据以及计算机软件生成的数据，处理、存贮和发送下行遥测数据到航天器遥测发射机(应答机)。处理、存储、分配来自地球站或其它航天器的遥控指令和数据以及航天器生成的控制指令和数据，生成航天器时钟，实施航天器计算机的管理，实现串行数据总线的管理以及航天器数据管理。
3.2
远置单元(RTU) remote terminal unit
配置在航天器不同部位，采集航天器的遥测数据，分配指令和数据的设备，也能完成闭环自主控制。
3.3
遥置总线接口(RBI) remote bus interface
配置于其它分系统、设备、科学仪器的串行数据总线接口板，用以实现CTU经串行数据总线和这些分系统、设备、科学仪器间的数据交换。
3.4
遥控单元(TCU) telecommand unit
接收来自航天器遥控接收机(应答机)的上行遥控信息(包括数据和指令)的设备。这些信息经处理生成直接开/关指令送用户或以串行加载指令的形式送往中央控制单元。
3.5
指令译码单元(CDU) command decoder unit
对上行遥控信息进行译码生成直接开/关指令的设备。
3.6
直接开/关指令 direct ON/OFF command
地球站或其它航天器以指令的格式上行传送到航天器上，由遥控单元、指令译码单元直接译码输出的开/关指令。
3.7
间接开/关指令 routed ON/OFF command
地球站或其它航天器以数据注入的格式上行传送到航天器上，经中央控制单元处理后，由远置单元输出的开/关指令，这类指令可以实时也可以延时输出。
3.8
航天器上开/关指令 on-board ON/OFF command
航天器运行过程中根据预先给定的算法和判据由航天器生成的指令。
4 总则
4.1 概述
航天器数据管理接口，应确保接口间的电气匹配和故障的隔离。
4.2 接口的类型
4.2.1 遥测通道是数管系统采集用户数据的接口。由于所采集数据的类型不同，遥测通道可以采用单根或数根传送线。也被分为如下几类：
a) 模拟通道：采集单端或双端输入的模拟信号；
b) 数字通道：采集8Nbit串行数字信号(N是正整数)；
c) 双电平数字通道：采集1bit状态数据，8bit状态数据编成一组(一个遥测字)；
d) 标时通道：采集单个事件发生的时间。
4.2.2 遥控通道是将数管系统的指令及数据传送到用户的接口。由于指令的类型不同，遥控通道也可以采用单根或数根传送线。被分为如下几类：
a) 开/关指令通道：以具有一定宽度的脉冲的形式提供给用户，用于驱动较大功率的负载；
b) 串行加载指令通道：向用户传送8Nbit的数据字(N是正整数)。
4.2.3 串行数据总线用于实现数管系统各模块间以及数管系统经远置总线接口和航天器分系统、设备、科学仪器间的信息传送。采用时分多路复用的原理传送PCM数据。
4.3 信号和电平的约定
4.3.1 串行数字信号(非归零电平码NRZ-L)
这类信号出现在遥测数字通道接口和遥控串行加载指令通道接口。对于遥测通道，串行数字信号是数管系统的输入；对于遥控通道，串行数字信号(数据字)是数管系统的输出。以正电压或开关断开表示数字信号的逻辑“1”，以零电压或开关接通表示数字信号的逻辑“0”。
4.3.2 采样信号和地址信号
这类信号用于串行数字信号的传送。当航天器特定分系统用户地址数量较少时，采样信号是由远置单元向用户直接提供的选通信号；当特定分系统的用户地址数量较多时(一般大于8)，则可以地址信号的形式向用户提供地址编码，再由该分系统自行完成地址译码生成相应地址的选通信号。
选通信号，无论是采样信号直接提供的还是地址信号译码所生成的，均为开关闭合信号。工作状态(即选通状态)，开关闭合；非工作状态，开关断开。电路设计要确保工作状态时，用户输入端为零电平。
4.3.3 双电平数字信号
双电平数字信号没有非工作状态，即“静止态”。
这类信号是遥测双电平数字通道的数据输入。以两个逻辑状态表示，正电压对应于逻辑“1”，零电压对应于逻辑“0”。
5 遥测通道接口
5.1 单端模拟通道
5.1.1 一般要求
一般要求如下：
a) 单端模拟输入由模拟信号输入线和模拟参数地线构成，其中模拟参数地线对所有模拟信号是共用的；
b) 模拟信号源的返回线连接到编码器的模拟参考地，模拟信号源的输出线连接到编码器的输入端(相对于返回线为正)；
c) 模拟信号输入线至模拟参考地之间的电压为模拟信号信息，这一电压被周期性的采样，进行模数转换而得到一个8bit，10bit或12bit的遥测字，其最高有效位(MSB)首先传送；
d) 单端模拟编码器输入有两个状态：在数据采集期间，编码器输入门是接通的；在非数据采集期间，编码器输入门是断开的；
e) 模拟通道由编码器采集是靠输入门接通，模拟信号取样并实现模数转换来实现的；
f) 模拟通道采用8bit编码，最低有效位为20mV，模数转换的量化误差为±10mV；当模拟通道采用10，12bit编码，最低有效位及量化误差按比例减小。
5.1.2 单端模拟通道信号源特性
单端模拟通道信号源特性的要求如下：
a) 信号源极性：相对于模拟信号源返回线为正极性；
b) 电压范围：0V～5.1V；
c) 设备通电时信号源输出阻抗：不大于5kΩ；
d) 设备断电时信号源输出阻抗：不小于100kΩ；
e) 过压能力：在模拟信号源的输出线上施加±12V的过电压(过压源的阻抗为2kΩ±0.3kΩ)应不损坏信号源；通过信号源的电流不大于15mA。
5.1.3 单端模拟通道输入编码器特性
单端模拟通道输入编码器特性的要求如下：
a) 输入阻抗
数据采集期间：10MΩ(B级最小值)，20MΩ(A级最小值)；
非数据采集期间：100MΩ(最小值)；
编码器断电期间：100MΩ(最小值)；
注：B级为现阶段要求：A级为条件具备后的要求，以下同。
b) 输入电容
数据采集期间：150pF(最大值)；
非数据采集期间：100pF(最大值)；
编码器断电期间：50pF(最大值)；
c) 漏电流
数据采集期间：500nA(最大值)；
非数据采集期间：100nA(最大值)；
编码器断电期间：50nA(最大值)，(最大输入电压为±10V时)；
d)过压能力
编码器供电期间：±12V(B级)，±16V(A级)；
(数据采集期间最大电流为10mA，非数据采集期间最大电流为1μA)；
编码器断电期间：±10V(最大值)，(最大电流为50nA)。
