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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
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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)
航天器測控和數據管理
第8部分：數據管理接口
1 范圍
本部分規定了航天器數據管理系統(以下簡稱數管系統)接口的總則以及遙測通道接口、遙控通道接口和串行數據總線接口。
本部分適用于航天器數管系統以及與數管系統接口的用戶。
2 規范性引用文件
下列文件中的條款通過本部分的引用而成為本部分的條款。凡是注日期的引用文件，其隨后所有的修改單(不包含勘誤的內容)或修訂版均不適用于本部分，然而，鼓勵根據本部分達成協議的各方研究是否可使用這些文件的最新版本。凡是不注日期的引用文件，其最新版本適用于本部分。
GJB 289A-1997 數字式時分制指令/響應型多路傳輸數據總線
GJB 727A-1998 航天測控系統術語與縮略語
3 術語和定義
GJB 727A-1998 確立的以及下列術語和定義適用于本部分。
3.1
中央單元(CTU) central terminal unit
數管系統的中央控制設備，它匯集來自遠置單元的采集數據、經串行數據總線傳送來的數據以及計算機軟件生成的數據，處理、存貯和發送下行遙測數據到航天器遙測發射機(應答機)。處理、存儲、分配來自地球站或其它航天器的遙控指令和數據以及航天器生成的控制指令和數據，生成航天器時鐘，實施航天器計算機的管理，實現串行數據總線的管理以及航天器數據管理。
3.2
遠置單元(RTU) remote terminal unit
配置在航天器不同部位，采集航天器的遙測數據，分配指令和數據的設備，也能完成閉環自主控制。
3.3
遙置總線接口(RBI) remote bus interface
配置于其它分系統、設備、科學儀器的串行數據總線接口板，用以實現CTU經串行數據總線和這些分系統、設備、科學儀器間的數據交換。
3.4
遙控單元(TCU) telecommand unit
接收來自航天器遙控接收機(應答機)的上行遙控信息(包括數據和指令)的設備。這些信息經處理生成直接開/關指令送用戶或以串行加載指令的形式送往中央控制單元。
3.5
指令譯碼單元(CDU) command decoder unit
對上行遙控信息進行譯碼生成直接開/關指令的設備。
3.6
直接開/關指令 direct ON/OFF command
地球站或其它航天器以指令的格式上行傳送到航天器上，由遙控單元、指令譯碼單元直接譯碼輸出的開/關指令。
3.7
間接開/關指令 routed ON/OFF command
地球站或其它航天器以數據注入的格式上行傳送到航天器上，經中央控制單元處理后，由遠置單元輸出的開/關指令，這類指令可以實時也可以延時輸出。
3.8
航天器上開/關指令 on-board ON/OFF command
航天器運行過程中根據預先給定的算法和判據由航天器生成的指令。
4 總則
4.1 概述
航天器數據管理接口，應確保接口間的電氣匹配和故障的隔離。
4.2 接口的類型
4.2.1 遙測通道是數管系統采集用戶數據的接口。由于所采集數據的類型不同，遙測通道可以采用單根或數根傳送線。也被分為如下幾類：
a) 模擬通道：采集單端或雙端輸入的模擬信號；
b) 數字通道：采集8Nbit串行數字信號(N是正整數)；
c) 雙電平數字通道：采集1bit狀態數據，8bit狀態數據編成一組(一個遙測字)；
d) 標時通道：采集單個事件發生的時間。
4.2.2 遙控通道是將數管系統的指令及數據傳送到用戶的接口。由于指令的類型不同，遙控通道也可以采用單根或數根傳送線。被分為如下幾類：
a) 開/關指令通道：以具有一定寬度的脈沖的形式提供給用戶，用于驅動較大功率的負載；
b) 串行加載指令通道：向用戶傳送8Nbit的數據字(N是正整數)。
4.2.3 串行數據總線用于實現數管系統各模塊間以及數管系統經遠置總線接口和航天器分系統、設備、科學儀器間的信息傳送。采用時分多路復用的原理傳送PCM數據。
4.3 信號和電平的約定
4.3.1 串行數字信號(非歸零電平碼NRZ-L)
這類信號出現在遙測數字通道接口和遙控串行加載指令通道接口。對于遙測通道，串行數字信號是數管系統的輸入；對于遙控通道，串行數字信號(數據字)是數管系統的輸出。以正電壓或開關斷開表示數字信號的邏輯“1”，以零電壓或開關接通表示數字信號的邏輯“0”。
4.3.2 采樣信號和地址信號
這類信號用于串行數字信號的傳送。當航天器特定分系統用戶地址數量較少時，采樣信號是由遠置單元向用戶直接提供的選通信號；當特定分系統的用戶地址數量較多時(一般大于8)，則可以地址信號的形式向用戶提供地址編碼，再由該分系統自行完成地址譯碼生成相應地址的選通信號。
選通信號，無論是采樣信號直接提供的還是地址信號譯碼所生成的，均為開關閉合信號。工作狀態(即選通狀態)，開關閉合；非工作狀態，開關斷開。電路設計要確保工作狀態時，用戶輸入端為零電平。
4.3.3 雙電平數字信號
雙電平數字信號沒有非工作狀態，即“靜止態”。
這類信號是遙測雙電平數字通道的數據輸入。以兩個邏輯狀態表示，正電壓對應于邏輯“1”，零電壓對應于邏輯“0”。
5 遙測通道接口
5.1 單端模擬通道
5.1.1 一般要求
一般要求如下：
a) 單端模擬輸入由模擬信號輸入線和模擬參數地線構成，其中模擬參數地線對所有模擬信號是共用的；
b) 模擬信號源的返回線連接到編碼器的模擬參考地，模擬信號源的輸出線連接到編碼器的輸入端(相對于返回線為正)；
c) 模擬信號輸入線至模擬參考地之間的電壓為模擬信號信息，這一電壓被周期性的采樣，進行模數轉換而得到一個8bit，10bit或12bit的遙測字，其最高有效位(MSB)首先傳送；
d) 單端模擬編碼器輸入有兩個狀態：在數據采集期間，編碼器輸入門是接通的；在非數據采集期間，編碼器輸入門是斷開的；
e) 模擬通道由編碼器采集是靠輸入門接通，模擬信號取樣并實現模數轉換來實現的；
f) 模擬通道采用8bit編碼，最低有效位為20mV，模數轉換的量化誤差為±10mV；當模擬通道采用10，12bit編碼，最低有效位及量化誤差按比例減小。
5.1.2 單端模擬通道信號源特性
單端模擬通道信號源特性的要求如下：
a) 信號源極性：相對于模擬信號源返回線為正極性；
b) 電壓范圍：0V～5.1V；
c) 設備通電時信號源輸出阻抗：不大于5kΩ；
d) 設備斷電時信號源輸出阻抗：不小于100kΩ；
e) 過壓能力：在模擬信號源的輸出線上施加±12V的過電壓(過壓源的阻抗為2kΩ±0.3kΩ)應不損壞信號源；通過信號源的電流不大于15mA。
5.1.3 單端模擬通道輸入編碼器特性
單端模擬通道輸入編碼器特性的要求如下：
a) 輸入阻抗
數據采集期間：10MΩ(B級最小值)，20MΩ(A級最小值)；
非數據采集期間：100MΩ(最小值)；
編碼器斷電期間：100MΩ(最小值)；
注：B級為現階段要求：A級為條件具備后的要求，以下同。
b) 輸入電容
數據采集期間：150pF(最大值)；
非數據采集期間：100pF(最大值)；
編碼器斷電期間：50pF(最大值)；
c) 漏電流
數據采集期間：500nA(最大值)；
非數據采集期間：100nA(最大值)；
編碼器斷電期間：50nA(最大值)，(最大輸入電壓為±10V時)；
d)過壓能力
編碼器供電期間：±12V(B級)，±16V(A級)；
(數據采集期間最大電流為10mA，非數據采集期間最大電流為1μA)；
編碼器斷電期間：±10V(最大值)，(最大電流為50nA)。
