4-3 Telemetry and Command Processing System for Experiments

OHASHI Hajime

Two telemetry and command processing systems are being prepared as part of the ground facilities by CRL to monitor and control CRL’s onboard equipment of ETS-VIII. One is for mobile communication experiments and another is for time comparing experiments. They have the almost same architecture but databases and amount of host hardware are adjusted for each target telemetry and command set respectively. So all telemetries and commands are transmitted through TT&C system of NASDA that CRL’s T&C systems communicate with ETS-VIII through NASDA’s TT&C system. Some of telemetries and commands from/to CRL’s onboard equipment which are critical for ETS-VIII satellite system safety are monitored and checked by NASDA’s TT&C system too. The other telemetries and commands are simply relayed by NASDA’s TT&C between CRL’s onboard equipment and CRL’s T&C systems. CRL’s T&C system have realtime and non-realtime servers and some terminals. Servers manage the communication with NASDA’s TT&C system, process telemetries and commands, and archive telemetry data and command history data. On each terminal, operators can monitor the status of onboard equipment and control them by sending commands. In this paper, the architecture of CRL’s T&C systems and their functions are introduced. Keywords ETS-VIII, Eighth Engineering Test Satellite, TT&C, Telemetry and Command, CCSDS, Ground segment

1 Introduction NASDA satellite control system through a network connection. The telemetry and command processing The CRL T&C system consists of a major system for experiments (hereinafter referred to shared unit to provide general-purpose com- as the CRL T&C system) is a ground facility mon functions, and dedicated units, incorpo- for monitoring the status of mission equip- rated therein, to provide processing functions ment which was developed by CRL and put dedicated to specific onboard equipment. onboard the ETS-VIII, through telemetry, and The mission equipment onboard the ETS- for editing and transmitting commands that VIII developed by CRL comprises (1) a com- turn on/off the equipment, alter operating munication subsystem whose objectives are modes, and set operating parameters. mobile communications and broadcast experi- In the ETS-VIII system, reception of ments (refer to “Configuration for mobile telemetry and transmission of commands are communication satellite system and broadcast- performed through NASDA satellite control ing satellite systems,” Article 3-2 in this spe- system and GN (Ground communication Net- cial issue) and (2) high-accuracy time compar- work). Consequently, the CRL T&C system ison equipment (refer to “Time comparison does not have an RF segment and is linked to equipment,” Article 3-10 in this special issue),

OHASHI Hajime 145 for each of which a dedicated T&C system is mented at the Koganei Headquarters. Both prepared. Both have the same architecture, have the same configuration except for the except for the contents of target telemetries scale of the database and hardware, and differ- and commands, a dedicated unit incorporated ent dedicated units are integrated into them. therein, and hardware scale. Both systems are connected separately to the The major shared unit consists of servers, NASDA satellite control system. terminals, and databases. Fig.1 shows the overall configuration of Java was selected as the software develop- the telemetry and command processing facility ment language, while XML was selected for for ETS-VIII experiments. The figure shows the database definition language; therefore, only the CRL-related portion. Fig.2 shows the the system is fundamentally OS-independent. configuration of the T&C system for commu- This paper reviews the configuration and nication experiments. The system for time functions of the major shared unit. comparison experiments does not include mobile terminals. 2 System configuration

2.1 Basic concept of configuration and its features The CRL T&C system consists of a major shared unit which provides general-purpose common functions and dedicated units which provide specific processing functions for specific onboard equipment. Dedicated units are integrated into the major shared unit. Since the functions of the major shared unit are Fig.1 System overview (only CRL-related defined primarily by the database, it can also portion) be used in other satellites by newly defining a database. The major shared unit consists of servers, terminals, databases, and a connection circuit with NASDA satellite control system. Databases are defined by XML in con- formity with the NASDA satellite control system. Due to the difficulty of editing XML directly, some tools for building the databases have been prepared. Fig.2 Configuration of T&C system for com- Several Windows PCs are used as host munication experiments hardware, and are linked through a LAN to constitute a system. Hardware configurations 2.2 Server can be optimized by selecting a number of The system is equipped with a real-time PCs and adjusting their throughputs according server and a non-real-time server; the real- to a processing load. Except for a few tools, time server talks to the NASDA satellite con- the system was developed in Java. Thus, it is trol system and performs telemetry and com- fundamentally OS-independent. mand processing in a real-time manner, while One T&C system for communication the non-real-time server reproduces stored experiments is implemented in the Kashima telemetries, receives telemetry information Space Research Center, and another system and exchanges control information in a batch for time comparison experiments is imple- manner.

146 Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003 A simulator simulates the NASDA satellite Several utilities are prepared to manage control system for development and tests of these databases. Databases are constructed, the CRL T&C system. modified and version controlled by operators with these utilities interactively. 2.3 Terminals The terminal provides a user interface. It 2.5 Dedicated units displays telemetry results and allows the oper- A dedicated unit is integrated into the ator to issue commands. Utility processing major shared unit and provides processing such as the building or modification of the functions dedicated to specific onboard equip- databases, is also performed from the termi- ment. nal. Several operators can log into the system In the CRL T&C system, there are two through terminals, and perform operations in dedicated systems: a BFN operating system specific windows to execute telemetry and for mobile communication experiments (refer command processing functions. All operators to the “BFN operating system,” Article 4-4 in logging into the system can open multiple this special issue); and a time comparison windows simultaneously. For command trans- experiment system. mission, to prevent two or more operators from transmitting commands simultaneously, 3 The NASDA satellite control sys- only one operator is given the authority to tem and the CRL T&C system transmit a command. 3.1 ETS-VIII telemetry and command 2.4 Databases and utilities processing system them The ETS-VIII telemetry and command The system includes a telemetry database, system adopts the CCSDS (Consultative Com- a command database, and an SOP (Satellite mittee for Space Data Systems) protocol. All Operation Procedure) database. telemetry and command information are The telemetry database defines how to enclosed in CCSDS packets, which are trans- derive a significant engineering value from a mitted between the satellite and a ground T&C raw telemetry data sequence, including the system. In the ETS-VIII project, only ground addresses at which each telemetry result is facilities of NASDA are permitted to directly stored, the storage form, and engineering transmit commands and receive telemetry value conversion curves. This database also information to and from the satellite. Experi- stores various parameters that define each mental users from CRL and other project telemetry view window. member organizations operate the onboard The command database saves information experimental equipment through the NASDA needed to edit commands, such as command satellite control system. Therefore, the CRL names in readable text format, as well as T&C system does not have an RF segment for methods for defining command parameters. directly communicating with the satellite, but An SOP is a kind of script language that is instead linked to the NASDA satellite con- describes the operation sequence, e.g., to trol system though a terrestrial data communi- determine whether the satellite’s conditions cation line. are adequate for a specific operation, and to transmit a command sequence if no problems 3.2 Overview of the NASDA satellite are detected. An SOP usually contains defini- control system tions of command sequence that are actually The NASDA satellite control system is an transmitted. Condition judgement, branching, integrated system that enables a handful of calling of a sub-SOP, etc. are possible in SOP operators to operate multiple satellites. execution. NASDA satellite control system consists

OHASHI Hajime 147 of a satellite operation control subsystem, a telemetry from equipment developed by the satellite data processing subsystem, a satellite experiment participants. operational planning subsystem, a satellite The HK telemetry is distributed after database management subsystem, and a satel- being converted to engineering value in the lite operation terminal subsystem. These sub- NASDA satellite control system. Because the systems are connected to a LAN. Further, an HK telemetry contains information related to orbital dynamics subsystem, satellite develop- the health of the whole satellite system, it is ment subsystem, GN, SN (Space Network: a monitored in the NASDA satellite control sys- satellite control network by DRTS; not used in tem. Thus, CRL can obtain telemetry results ETS-VIII), a satellite simulator, participants that have been converted to engineering value performing the experiment, etc. are connected from NASDA. On the other hand, the experi- to this LAN, taking the appropriate security mental telemetry is the information specific to measures. the onboard experimental equipment. Since it The HAC experiment system of NASDA has no direct effect on the health of the whole (refer to “High accuracy clock (HAC),” Arti- satellite system, it is neither converted to engi- cle 3-9 in this special issue), which is closely neering nor monitored by the NASDA satellite related to the time comparison experiments, is control system, and is relayed to CRL as is. also connected to the NASDA satellite control Further, the experimental telemetry is system as one of the experimental participants divided into two kinds: RIM2 (Remote Inter- to perform the experiment by exchanging face Module 2) telemetry; and packet teleme- experimental data with the T&C system for try. Here, the RIM2 is one remote interface CRL time comparison experiments. module for mission equipment out of two RIMs providing compatibility between 3.3 Connection with the NASDA satel- onboard equipment that have a legacy teleme- lite control system try and command interface and CCSDS sys- 3.3.1 Network tem by hard wired connection. The CRL T&C system is linked to the RIM2 telemetry is from onboard experi- NASDA satellite control system through a mental equipment, each having the telemetry dedicated router and leased data lines. Since and command interface of the conventional two T&C system users are distinguished—a RIM format, and comprises raw telemetry data user of mobile communication experiments being enclosed in CCSDS packets by RIM2. and a user of time comparison experiments, Packet telemetry is also from onboard two distinct connection points are provided, experimental equipment, but each equipment one for each user. The one is connected to has a CCSDS interface. Kashima, the other is connected to Koganei. Extraction of the experimental telemetry The CRL T&C system is connected to no from the CCSDS packet, conversion to engi- other networks, including the internal CRL neering values, limit check, etc. are performed network, for security reasons. on the CRL T&C system. These processing of Digital leased line services are used to packet telemetry are generally assigned to a implement the connection. A transmission dedicated unit corresponding to the equipment speed of about 128 kbps is assumed. from which the telemetry comes. 3.3.2 Telemetry information Telemetry data is generally distributed in Two types of telemetry information are real-time manner. However, when reception distributed to operators performing the experi- fails due to conditions of the CRL T&C sys- ment. The one is HK (House Keeping) tem, the telemetry data stored in the NASDA telemetry, such as temperatures and satellite satellite control system can be retrieved in attitude information which are from the satel- batch manner afterward. Note that the period lite bus system. The other is experimental for which telemetry data is stored in the

148 Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003 NASDA satellite control system is limited. A data distribution protocol is used to 3.3.3 Command information exchange these pieces of information and to As with the telemetry, there are two types receive the stored telemetry data from of command information. NASDA in a batch manner. The data distribu- The HK command is such a command for tion protocol is NASDA original protocol for switching equipment ON/OFF. The CRL practical data exchange. With this protocol, T&C system sends a command in readable control information is exchanged via e-mail text format to the NASDA satellite control first, followed by transferring data with FTP. system, from which the NASDA satellite con- This protocol is built into the CRL T&C sys- trol system constructs a CCSDS packet and tem. transmits it to the satellite. Since the HK In addition, data exchange to and from the command is likely to affect the health of the NASDA HAC experimental facility is also whole satellite, the NASDA satellite control performed using this data distribution proto- system checks its suitability before transmit- col. ting it to the satellite. 3.3.5 Time synchronization On the other hand, the experimental com- Since the CRL T&C system is incorporat- mand alters the onboard equipment mode and ed into the LAN of the NASDA satellite con- sets its operational parameters. The CRL trol system, system time of the CRL T&C sys- T&C system construct a CCSDS packet of the tem is synchronized to the NASDA system by command and transmits it. The NASDA satel- accessing the NTP server in the NASDA sys- lite control system then relays it to the satellite tem. without checking its suitability. From CRL T&C system, commands are 4 Configuration and functions of transmitted in a real-time manner. Although servers the NASDA satellite control system has various command functions for practical satellite Servers in the major shared unit are a real- operations, such as transmitting a command time server, a non-real-time server, a network automatically at a specified time, it is not storage, a firewall, and a simulator of the assumed that the CRL uses these functions for NASDA satellite control system. An overview the sake of the experiments. of the function of each of these components is 3.3.4 Operational information given below. The CRL T&C system exchanges operational planning information, orbital informa- 4.1 Real-time server tion, etc. with the NASDA satellite control 4.1.1 Communication with the NASDA system in addition to the telemetry and com- satellite control system mand. The real-time server executes reception of The operational plan is the schedule infor- telemetry and transmission of a command in mation for the satellite operation, including an real-time manner. orbit control plan for the satellite, an experi- 4.1.2 Reception, engineering value ment schedule, etc. Experimental time conversion, limit check, and requests are submitted to NASDA for reserv- storing telemetry ing the satellite operational time, then coordi- The real-time server performs the follow- nated and fixed schedule information is ing operations to telemetry distributed from returned from NASDA. the NASDA satellite control system. Note Orbital information contains orbit determi- that a dedicated unit performs functions nation results and forecasted orbital informa- except storing telemetry data if the unit is suit- tion including predicted results of orbit control ed to the telemetry. Moreover, for HK teleme- maneuvers. It is distributed periodically. try, since telemetry converted into engineering

OHASHI Hajime 149 value is distributed from the NASDA satellite server to allow the operator to monitor teleme- control system, only limit checks and storing tries using the same display as the real-time are performed. telemetry monitor. Unpacking of telemetry data packets 4.2.2 Statistical processing of stored Raw telemetry data is extracted from telemetry CCSDS packets. Fundamental statistical processing is per- Conversion into engineering value formed upon a set of reproduced telemetry The engineering value is calculated from data. the unpacked raw data, and the status This processing displays moving averages, information is retrieved. maxima, and minima, and graphically depicts Telemetry storage the correlation between telemetries. The telemetry data is stored in network A straight vertical lines placed at the com- storage. mand execution time can be displayed over 4.1.3 Command processing the reproduced telemetry graphs to confirm Command editing and transmission whether the command execution is affected by A command sequence is interactively the status of onboard equipment. transmitted by the operator by executing 4.2.3 Communication with NASDA’s an SOP through a command processing system by data distribution pro- window on the terminal. The real-time tocol server relays command transmission The non-real-time server handles commu- between the terminal and the NASDA nications between the NASDA satellite control satellite control system. In this relaying, a system and the CRL T&C system, except readable text (character strings representa- telemetry reception and command transmis- tion of command) form of command that sion, by real-time server in a real-time manner. is compatible with the NASDA satellite Two major types of communications are as control system is used for the HK com- below. mand; CCSDS packets, in which com- Telemetry file download mands are packed, are used for the experi- While the CRL system is switched off or ment commands. down and telemetry data during this period Verification is required, telemetry data is downloaded When a command is transmitted, the from the NASDA as a file by the data dis- NASDA satellite control system returns an tribution protocol. Since the downloaded acknowledgement, and the ETS-VIII satel- file is saved as an image of real-time trans- lite returns an execution result answer, mission, the file is subjected to the same both as a part of telemetry. The real-time real-time telemetry processing as that for server returns the execution result to the the real-time telemetry stream. terminal as one of its telemetry processing Transmission/ reception of operational functions. information Command history management Operational plans, orbital information, Pairs of a transmitted command and a HAC data, etc. are transmitted and result of verification are recorded and received by the data distribution protocol. stored as a command history into the net- 4.2.4 Backup of real-time server work storage. In the event of a failure of the real-time server, the non-real-time server will perform 4.2 Non-real-time server its functions for backup. Changeover (starting 4.2.1 Stored telemetry reproduction of the real-time server process) is done manu- Stored telemetry data for an arbitrary past ally by the operator. period is reproduced by the non-real-time

150 Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003 4.3 Network storage 5.2 Telemetry processing Network storage stores received telemetry Telemetry processing involves displaying data, command history data, and the database. telemetry and limit checks of telemetry values. The prepared capacity is adequate to store all The limit check is the function to issue an alert telemetry data received throughout an experi- when the telemetry values falls outside the ment period, all command history data, and range which is defined precedentedly and the database data. To ensure reliability, dedi- stored in a database. As a value range, the cated hardware based on a RAID system is operator can define two range types: the cau- adopted. tion (a range that calls the operator’s atten- tion); and the action (variation in the value 4.4 Firewall that necessitates some counter-actions). A firewall function is implemented to pro- The following four types of telemetry tect both the NASDA satellite control system view are available. and the CRL T&C system at the juncture of List view these systems. All related telemetries are displayed col- lectively in a single window in list form. 4.5 NASDA satellite control system All values in the window are updated simulator whenever a new telemetry value is The simulator simulates the NASDA satel- received from the satellite. lite control system both for development and Time series list view testing the CRL T&C system. It distributes Several related telemetries are arranged pseudo telemetry data for the tests, receives to form a telemetry array on a horizontal false commands, and performs pseudo trans- axis, and telemetry arrays at different mission reception of operational information receiving times are stacked vertically, by the data distribution protocol. whereby time series variations of related telemetries are shown in table form. The 5 Configuration and functions of stacked telemetry arrays can be divided terminals along the vertical axis: one stacked arrays are updated in real-time; while other 5.1 Configuration of terminals stacked arrays show past data. Several PCs are provided as terminals, on Graphical view any one of which the operator can execute Several telemetries are shown in one telemetry processing and command process- chart. A single window can have up to ing. Data is given and received between four charts, on each chart up to four telemetry and command processing processes telemetries can be plotted. While the on the terminal and those on the servers by default graph selection and parameters are interprocess communications. defined in the database, they can be tem- The Kashima system for mobile communi- porarily or permanently changed by the cation experiments have several remote termi- operator. nals that are linked to the Kashima system by Block diagram view PHS (or cellular phone) to enable telemetry The configuration of onboard equipment monitoring and command transmission even is shown in a block diagram, and at the in the field of a mobile experiment. Although position of each component, telemetry val- there are some restrictions on the line speed of ues corresponding to that component are PHS (or cellular phone), adequate perform- displayed. The telemetry values are updat- ance for experiments is maintained in practice. ed in real-time. Results of the limit check are indicated by changing the color of component blocks.

OHASHI Hajime 151 5.3 Command processing experimental results. Command transmission is conducted by System management executing the SOP. The operator calls and This utility controls hardware configura- executes the SOP appropriate to the required tion, user registration, and so on. operation from a previously prepared database. Commands to be transmitted are 5.5 GUI examples defined on the SOP. GUI examples are shown in Figs.3 to 10. The SOP checks telemetry data and con- firms whether the satellite is capable of executing the operation. If so, the SOP transmits a series of commands automatically, or manu- ally step-by-step. The operator can specify whether to perform verification for each step to proceed to the next command after confirm- ing completion of execution. An authorization mechanism is prepared to allow only one authorized operator to transmit commands exclusively.

5.4 Utility functions The following utility functions are prepared in the CRL T&C system. Fig.3 GUI example, Telemetry list view Editing and transmission reception of operational plan The operational plan is transmitted and received to coordinate the requested experiment time and the orbit control and other aspects of the ETS-VIII satellite system operation. Reception of orbital information Orbital information needed to analyze experimental results in detail is received periodically. Building database Fig.4 GUI example, Telemetry time series This utility edits and revises the teleme- view try database, the command database, and the SOP interactively. Since certain database tools were developed using a pro- gramming language other than Java, this utility only works on Windows OSs at this time. Terminal window printing This utility prints hard copies of the telemetry processing window and the command processing window in the terminal. Telemetry data file output The engineering values are output in the Fig.5 GUI example, Telemetry graph view form of CSV to enable further analysis of

152 Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003 Fig.9 GUI example, SOP defining window

Fig.6 GUI example, Telemetry block diagram view 1

Fig.10 GUI example, Telemetry database editing window

6 Integration of dedicated unit Fig.7 GUI example, Telemetry block dia- into the major shared unit gram view 2 Interface specifications between the dedicated unit and the major shared unit were coordinated for each dedicated unit individual- ly, since the number of dedicated units in the CRL T&C system is few. No general-purpose interface specifications were defined. Fundamental interfaces in the current implementation are as follows. Telemetry processing In telemetry processing, from the need for real-time operations, and the need for the capability to display telemetries Fig.8 GUI example, Command transmitting processed by the dedicated unit together window with other telemetries in the same window, a processing program of the dedicated unit was built into the major shared unit and made to work on any terminal. More specifically, a Java class created for the

OHASHI Hajime 153 dedicated unit was included in the major shared unit. Since there are some dynamic alterations of the diagrams that represent the configuration of equipment according to the command transmission, the files of the block diagram created by the dedicated unit in each case are accessed via file sharing. Command processing Fig.11 Photograph of T&C system for com- Any command transmitted by the dedi- munication experiments 1 cated unit is a packet command. Com- mands registered in advance as SOPs, i.e., commands are previously constructed and filed, are transmitted by normal SOP execution. Command construction is execut- ed on the dedicated unit, and commands are given to the major shared unit by file sharing.

7 Afterword Fig.12 Photograph of T&C system for communication experiments 2 Development of the CRL T&C system was carried out by placing orders to manufacturers show host equipment of the major shared unit in piecemeal fashion corresponding to areas of for communication experiments installed in development: design work; software manufac- the Kashima Space Research Center. turing work based design; and database con- On the other hand, CRL performed inter- struction tool manufacturing work. In starting face coordination alongside NASDA to deter- the design work, the author formulated guide- mine interface specifications with the NASDA lines of the configuration corresponding to a satellite control system in the early design basic design. Manufacturers then gave shape stage. There was an option to borrow the soft- thereto in terms of system implementation and ware system from NASDA to ease interfacing modified the basic design according to its con- work, but it was finally decided due to the sys- tent. The software manufacturing was fin- tem scale and other factors to develop original ished by fiscal 2002. system software. Hardware, such as host PCs, and OS were Henceforth, system test, adjustment, and prepared by the CRL; implementation of the training of operators are planned to proceed in T&C system for communication experiments accordance with the ETS-VIII launch sched- and for time comparison experiments (i.e., ule. The interface test with the NASDA satel- installation of the software and database con- lite control system is a major testing milestone struction) are being undertaken with the sup- and is to be carried forward in close coopera- port of the manufacturers. Figs.11 and 12 tion with NASDA.

OHASHI Hajime Senior Researcher, Space Data Trans- mission Group, Wireless Communica- tions Division Satellite Communication Engineering

154 Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003