1 Introduction

The telemetry and command processingsystem for experiments (hereinafter referred toas the CRL T&C system) is a ground facilityfor monitoring the status of mission equip-ment which was developed by CRL and putonboard the ETS-VIII, through telemetry, andfor editing and transmitting commands thatturn on/off the equipment, alter operatingmodes, and set operating parameters.

In the ETS-VIII system, reception oftelemetry and transmission of commands areperformed through NASDA satellite controlsystem and GN (Ground communication Net-work). Consequently, the CRL T&C systemdoes not have an RF segment and is linked to

NASDA satellite control system through a net-work connection.

The CRL T&C system consists of a majorshared unit to provide general-purpose com-mon functions, and dedicated units, incorpo-rated therein, to provide processing functionsdedicated to specific onboard equipment.

The mission equipment onboard the ETS-VIII developed by CRL comprises (1) a com-munication subsystem whose objectives aremobile communications and broadcast experi-ments (refer to “Configuration for mobilecommunication satellite system and broadcast-ing satellite systems,” Article 3-2 in this spe-cial issue) and (2) high-accuracy time compar-ison equipment (refer to “Time comparisonequipment,” Article 3-10 in this special issue),

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4-3 Telemetry and Command ProcessingSystem for Experiments

OHASHI Hajime

Two telemetry and command processing systems are being prepared as part of theground facilities by CRL to monitor and control CRL’s onboard equipment of ETS-VIII. Oneis for mobile communication experiments and another is for time comparing experiments.They have the almost same architecture but databases and amount of host hardware areadjusted for each target telemetry and command set respectively.

So all telemetries and commands are transmitted through TT&C system of NASDA thatCRL’s T&C systems communicate with ETS-VIII through NASDA’s TT&C system. Some oftelemetries and commands from/to CRL’s onboard equipment which are critical for ETS-VIIIsatellite system safety are monitored and checked by NASDA’s TT&C system too. The othertelemetries and commands are simply relayed by NASDA’s TT&C between CRL’s onboardequipment and CRL’s T&C systems.

CRL’s T&C system have realtime and non-realtime servers and some terminals. Serversmanage the communication with NASDA’s TT&C system, process telemetries and com-mands, and archive telemetry data and command history data. On each terminal, operatorscan 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

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for each of which a dedicated T&C system isprepared. Both have the same architecture,except for the contents of target telemetriesand commands, a dedicated unit incorporatedtherein, and hardware scale.

The major shared unit consists of servers,terminals, and databases.

Java was selected as the software develop-ment language, while XML was selected forthe database definition language; therefore,the system is fundamentally OS-independent.

This paper reviews the configuration andfunctions of the major shared unit.

2 System configuration

2.1 Basic concept of configurationand its features

The CRL T&C system consists of a majorshared unit which provides general-purposecommon functions and dedicated units whichprovide specific processing functions for spe-cific onboard equipment. Dedicated units areintegrated into the major shared unit. Sincethe functions of the major shared unit aredefined primarily by the database, it can alsobe used in other satellites by newly defining adatabase.

The major shared unit consists of servers,terminals, databases, and a connection circuitwith NASDA satellite control system.

Databases are defined by XML in con-formity with the NASDA satellite control sys-tem. Due to the difficulty of editing XMLdirectly, some tools for building the databaseshave been prepared.

Several Windows PCs are used as hosthardware, and are linked through a LAN toconstitute a system. Hardware configurationscan be optimized by selecting a number ofPCs and adjusting their throughputs accordingto a processing load. Except for a few tools,the system was developed in Java. Thus, it isfundamentally OS-independent.

One T&C system for communicationexperiments is implemented in the KashimaSpace Research Center, and another systemfor time comparison experiments is imple-

mented at the Koganei Headquarters. Bothhave the same configuration except for thescale of the database and hardware, and differ-ent dedicated units are integrated into them.Both systems are connected separately to theNASDA satellite control system.

Fig.1 shows the overall configuration ofthe telemetry and command processing facilityfor ETS-VIII experiments. The figure showsonly the CRL-related portion. Fig.2 shows theconfiguration of the T&C system for commu-nication experiments. The system for timecomparison experiments does not includemobile terminals.

2.2 ServerThe system is equipped with a real-time

server and a non-real-time server; the real-time server talks to the NASDA satellite con-trol system and performs telemetry and com-mand processing in a real-time manner, whilethe non-real-time server reproduces storedtelemetries, receives telemetry informationand exchanges control information in a batchmanner.

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

System overview (only CRL-relatedportion)

Fig.1

Configuration of T&C system for com-munication experiments

Fig.2

A simulator simulates the NASDA satellitecontrol system for development and tests ofthe CRL T&C system.

2.3 TerminalsThe terminal provides a user interface. It

displays telemetry results and allows the oper-ator to issue commands. Utility processingsuch as the building or modification of thedatabases, is also performed from the termi-nal. Several operators can log into the systemthrough terminals, and perform operations inspecific windows to execute telemetry andcommand processing functions. All operatorslogging into the system can open multiplewindows simultaneously. For command trans-mission, to prevent two or more operatorsfrom transmitting commands simultaneously,only one operator is given the authority totransmit a command.

2.4 Databases and utilities processingthem

The system includes a telemetry database,a command database, and an SOP (SatelliteOperation Procedure) database.

The telemetry database defines how toderive a significant engineering value from araw telemetry data sequence, including theaddresses at which each telemetry result isstored, the storage form, and engineeringvalue conversion curves. This database alsostores various parameters that define eachtelemetry view window.

The command database saves informationneeded to edit commands, such as commandnames in readable text format, as well asmethods for defining command parameters.

An SOP is a kind of script language thatdescribes the operation sequence, e.g., todetermine whether the satellite’s conditionsare adequate for a specific operation, and totransmit a command sequence if no problemsare detected. An SOP usually contains defini-tions of command sequence that are actuallytransmitted. Condition judgement, branching,calling of a sub-SOP, etc. are possible in SOPexecution.

Several utilities are prepared to managethese databases. Databases are constructed,modified and version controlled by operatorswith these utilities interactively.

2.5 Dedicated unitsA dedicated unit is integrated into the

major shared unit and provides processingfunctions dedicated to specific onboard equip-ment.

In the CRL T&C system, there are twodedicated systems: a BFN operating systemfor mobile communication experiments (referto the “BFN operating system,” Article 4-4 inthis special issue); and a time comparisonexperiment system.

3 The NASDA satellite control sys-tem and the CRL T&C system

3.1 ETS-VIII telemetry and commandsystem

The ETS-VIII telemetry and commandsystem adopts the CCSDS (Consultative Com-mittee for Space Data Systems) protocol. Alltelemetry and command information areenclosed in CCSDS packets, which are trans-mitted between the satellite and a ground T&Csystem. In the ETS-VIII project, only groundfacilities of NASDA are permitted to directlytransmit commands and receive telemetryinformation to and from the satellite. Experi-mental users from CRL and other projectmember organizations operate the onboardexperimental equipment through the NASDAsatellite control system. Therefore, the CRLT&C system does not have an RF segment fordirectly communicating with the satellite, butis instead linked to the NASDA satellite con-trol system though a terrestrial data communi-cation line.

3.2 Overview of the NASDA satellitecontrol system

The NASDA satellite control system is anintegrated system that enables a handful ofoperators to operate multiple satellites.

NASDA satellite control system consists

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of a satellite operation control subsystem, asatellite data processing subsystem, a satelliteoperational planning subsystem, a satellitedatabase management subsystem, and a satel-lite operation terminal subsystem. These sub-systems are connected to a LAN. Further, anorbital dynamics subsystem, satellite develop-ment subsystem, GN, SN (Space Network: asatellite control network by DRTS; not used inETS-VIII), a satellite simulator, participantsperforming the experiment, etc. are connectedto this LAN, taking the appropriate securitymeasures.

The HAC experiment system of NASDA(refer to “High accuracy clock (HAC),” Arti-cle 3-9 in this special issue), which is closelyrelated to the time comparison experiments, isalso connected to the NASDA satellite controlsystem as one of the experimental participantsto perform the experiment by exchangingexperimental data with the T&C system forCRL time comparison experiments.

3.3 Connection with the NASDA satel-lite control system

3.3.1 NetworkThe CRL T&C system is linked to the

NASDA satellite control system through adedicated router and leased data lines. Sincetwo T&C system users are distinguished—auser of mobile communication experimentsand a user of time comparison experiments,two distinct connection points are provided,one for each user. The one is connected toKashima, the other is connected to Koganei.The CRL T&C system is connected to noother networks, including the internal CRLnetwork, for security reasons.

Digital leased line services are used toimplement the connection. A transmissionspeed of about 128 kbps is assumed.3.3.2 Telemetry information

Two types of telemetry information aredistributed to operators performing the experi-ment. The one is HK (House Keeping)telemetry, such as temperatures and satelliteattitude information which are from the satel-lite bus system. The other is experimental

telemetry from equipment developed by theexperiment participants.

The HK telemetry is distributed afterbeing converted to engineering value in theNASDA satellite control system. Because theHK telemetry contains information related tothe health of the whole satellite system, it ismonitored in the NASDA satellite control sys-tem. Thus, CRL can obtain telemetry resultsthat have been converted to engineering valuefrom NASDA. On the other hand, the experi-mental telemetry is the information specific tothe onboard experimental equipment. Since ithas no direct effect on the health of the wholesatellite system, it is neither converted to engi-neering nor monitored by the NASDA satellitecontrol system, and is relayed to CRL as is.

Further, the experimental telemetry isdivided into two kinds: RIM2 (Remote Inter-face Module 2) telemetry; and packet teleme-try. Here, the RIM2 is one remote interfacemodule for mission equipment out of twoRIMs providing compatibility betweenonboard equipment that have a legacy teleme-try and command interface and CCSDS sys-tem by hard wired connection.

RIM2 telemetry is from onboard experi-mental equipment, each having the telemetryand command interface of the conventionalRIM format, and comprises raw telemetry databeing enclosed in CCSDS packets by RIM2.

Packet telemetry is also from onboardexperimental equipment, but each equipmenthas a CCSDS interface.

Extraction of the experimental telemetryfrom the CCSDS packet, conversion to engi-neering values, limit check, etc. are performedon the CRL T&C system. These processing ofpacket telemetry are generally assigned to adedicated unit corresponding to the equipmentfrom which the telemetry comes.

Telemetry data is generally distributed inreal-time manner. However, when receptionfails due to conditions of the CRL T&C sys-tem, the telemetry data stored in the NASDAsatellite control system can be retrieved inbatch manner afterward. Note that the periodfor which telemetry data is stored in the

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

NASDA satellite control system is limited.3.3.3 Command information

As with the telemetry, there are two typesof command information.

The HK command is such a command forswitching equipment ON/OFF. The CRLT&C system sends a command in readabletext format to the NASDA satellite controlsystem, from which the NASDA satellite con-trol system constructs a CCSDS packet andtransmits it to the satellite. Since the HKcommand is likely to affect the health of thewhole satellite, the NASDA satellite controlsystem checks its suitability before transmit-ting it to the satellite.

On the other hand, the experimental com-mand alters the onboard equipment mode andsets its operational parameters. The CRLT&C system construct a CCSDS packet of thecommand and transmits it. The NASDA satel-lite control system then relays it to the satellitewithout checking its suitability.

From CRL T&C system, commands aretransmitted in a real-time manner. Althoughthe NASDA satellite control system has vari-ous command functions for practical satelliteoperations, such as transmitting a commandautomatically at a specified time, it is notassumed that the CRL uses these functions forthe sake of the experiments.3.3.4 Operational information

The CRL T&C system exchanges opera-tional planning information, orbital informa-tion, etc. with the NASDA satellite controlsystem in addition to the telemetry and com-mand.

The operational plan is the schedule infor-mation for the satellite operation, including anorbit control plan for the satellite, an experi-ment schedule, etc. Experimental timerequests are submitted to NASDA for reserv-ing the satellite operational time, then coordi-nated and fixed schedule information isreturned from NASDA.

Orbital information contains orbit determi-nation results and forecasted orbital informa-tion including predicted results of orbit controlmaneuvers. It is distributed periodically.

A data distribution protocol is used toexchange these pieces of information and toreceive the stored telemetry data fromNASDA in a batch manner. The data distribu-tion protocol is NASDA original protocol forpractical data exchange. With this protocol,control information is exchanged via e-mailfirst, followed by transferring data with FTP.This protocol is built into the CRL T&C sys-tem.

In addition, data exchange to and from theNASDA HAC experimental facility is alsoperformed using this data distribution proto-col.3.3.5 Time synchronization

Since the CRL T&C system is incorporat-ed into the LAN of the NASDA satellite con-trol system, system time of the CRL T&C sys-tem is synchronized to the NASDA system byaccessing the NTP server in the NASDA sys-tem.

4 Configuration and functions ofservers

Servers in the major shared unit are a real-time server, a non-real-time server, a networkstorage, a firewall, and a simulator of theNASDA satellite control system. An overviewof the function of each of these components isgiven below.

4.1 Real-time server4.1.1 Communication with the NASDA

satellite control systemThe real-time server executes reception of

telemetry and transmission of a command inreal-time manner.4.1.2 Reception, engineering value

conversion, limit check, andstoring telemetry

The real-time server performs the follow-ing operations to telemetry distributed fromthe NASDA satellite control system. Notethat a dedicated unit performs functionsexcept storing telemetry data if the unit is suit-ed to the telemetry. Moreover, for HK teleme-try, since telemetry converted into engineering

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value is distributed from the NASDA satellitecontrol system, only limit checks and storingare performed.Unpacking of telemetry data packets

Raw telemetry data is extracted fromCCSDS packets.

Conversion into engineering valueThe engineering value is calculated from

the unpacked raw data, and the statusinformation is retrieved.

Telemetry storageThe telemetry data is stored in network

storage.4.1.3 Command processingCommand editing and transmission

A command sequence is interactivelytransmitted by the operator by executingan SOP through a command processingwindow on the terminal. The real-timeserver relays command transmissionbetween the terminal and the NASDAsatellite control system. In this relaying, areadable text (character strings representa-tion of command) form of command thatis compatible with the NASDA satellitecontrol system is used for the HK com-mand; CCSDS packets, in which com-mands are packed, are used for the experi-ment commands.

VerificationWhen a command is transmitted, the

NASDA satellite control system returns anacknowledgement, and the ETS-VIII satel-lite returns an execution result answer,both as a part of telemetry. The real-timeserver returns the execution result to theterminal as one of its telemetry processingfunctions.

Command history managementPairs of a transmitted command and a

result of verification are recorded andstored as a command history into the net-work storage.

4.2 Non-real-time server4.2.1 Stored telemetry reproduction

Stored telemetry data for an arbitrary pastperiod is reproduced by the non-real-time

server to allow the operator to monitor teleme-tries using the same display as the real-timetelemetry monitor.4.2.2 Statistical processing of stored

telemetryFundamental statistical processing is per-

formed upon a set of reproduced telemetrydata.

This processing displays moving averages,maxima, and minima, and graphically depictsthe correlation between telemetries.

A straight vertical lines placed at the com-mand execution time can be displayed overthe reproduced telemetry graphs to confirmwhether the command execution is affected bythe status of onboard equipment.4.2.3 Communication with NASDA’s

system by data distribution pro-tocol

The non-real-time server handles commu-nications between the NASDA satellite controlsystem and the CRL T&C system, excepttelemetry reception and command transmis-sion, by real-time server in a real-time manner.Two major types of communications are asbelow.Telemetry file download

While the CRL system is switched off ordown and telemetry data during this periodis required, telemetry data is downloadedfrom the NASDA as a file by the data dis-tribution protocol. Since the downloadedfile is saved as an image of real-time trans-mission, the file is subjected to the samereal-time telemetry processing as that forthe real-time telemetry stream.

Transmission/ reception of operationalinformation

Operational plans, orbital information,HAC data, etc. are transmitted andreceived by the data distribution protocol.

4.2.4 Backup of real-time serverIn the event of a failure of the real-time

server, the non-real-time server will performits functions for backup. Changeover (startingof the real-time server process) is done manu-ally by the operator.

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4.3 Network storageNetwork storage stores received telemetry

data, command history data, and the database.The prepared capacity is adequate to store alltelemetry data received throughout an experi-ment period, all command history data, andthe database data. To ensure reliability, dedi-cated hardware based on a RAID system isadopted.

4.4 FirewallA firewall function is implemented to pro-

tect both the NASDA satellite control systemand the CRL T&C system at the juncture ofthese systems.

4.5 NASDA satellite control systemsimulator

The simulator simulates the NASDA satel-lite control system both for development andtesting the CRL T&C system. It distributespseudo telemetry data for the tests, receivesfalse commands, and performs pseudo trans-mission reception of operational informationby the data distribution protocol.

5 Configuration and functions ofterminals

5.1 Configuration of terminalsSeveral PCs are provided as terminals, on

any one of which the operator can executetelemetry processing and command process-ing. Data is given and received betweentelemetry and command processing processeson the terminal and those on the servers byinterprocess communications.

The Kashima system for mobile communi-cation experiments have several remote termi-nals that are linked to the Kashima system byPHS (or cellular phone) to enable telemetrymonitoring and command transmission evenin the field of a mobile experiment. Althoughthere are some restrictions on the line speed ofPHS (or cellular phone), adequate perform-ance for experiments is maintained in practice.

5.2 Telemetry processingTelemetry processing involves displaying

telemetry and limit checks of telemetry values.The limit check is the function to issue an alertwhen the telemetry values falls outside therange which is defined precedentedly andstored in a database. As a value range, theoperator can define two range types: the cau-tion (a range that calls the operator’s atten-tion); and the action (variation in the valuethat necessitates some counter-actions).

The following four types of telemetryview are available.List view

All related telemetries are displayed col-lectively in a single window in list form.All values in the window are updatedwhenever a new telemetry value isreceived from the satellite.

Time series list viewSeveral related telemetries are arranged

to form a telemetry array on a horizontalaxis, and telemetry arrays at differentreceiving times are stacked vertically,whereby time series variations of relatedtelemetries are shown in table form. Thestacked telemetry arrays can be dividedalong the vertical axis: one stacked arraysare updated in real-time; while otherstacked arrays show past data.

Graphical viewSeveral telemetries are shown in one

chart. A single window can have up tofour charts, on each chart up to fourtelemetries can be plotted. While thedefault graph selection and parameters aredefined in the database, they can be tem-porarily or permanently changed by theoperator.

Block diagram viewThe configuration of onboard equipment

is shown in a block diagram, and at theposition of each component, telemetry val-ues corresponding to that component aredisplayed. The telemetry values are updat-ed in real-time. Results of the limit checkare indicated by changing the color ofcomponent blocks.

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5.3 Command processingCommand transmission is conducted by

executing the SOP. The operator calls andexecutes the SOP appropriate to the requiredoperation from a previously prepared data-base. Commands to be transmitted aredefined on the SOP.

The SOP checks telemetry data and con-firms whether the satellite is capable of exe-cuting the operation. If so, the SOP transmitsa series of commands automatically, or manu-ally step-by-step. The operator can specifywhether to perform verification for each stepto proceed to the next command after confirm-ing completion of execution.

An authorization mechanism is prepared toallow only one authorized operator to transmitcommands exclusively.

5.4 Utility functionsThe following utility functions are pre-

pared in the CRL T&C system.Editing and transmission reception ofoperational plan

The operational plan is transmitted andreceived to coordinate the requested exper-iment time and the orbit control and otheraspects of the ETS-VIII satellite systemoperation.

Reception of orbital informationOrbital information needed to analyze

experimental results in detail is receivedperiodically.

Building databaseThis utility edits and revises the teleme-

try database, the command database, andthe SOP interactively. Since certain data-base tools were developed using a pro-gramming language other than Java, thisutility only works on Windows OSs at thistime.

Terminal window printingThis utility prints hard copies of the

telemetry processing window and the com-mand processing window in the terminal.

Telemetry data file outputThe engineering values are output in the

form of CSV to enable further analysis of

experimental results.System management

This utility controls hardware configura-tion, user registration, and so on.

5.5 GUI examplesGUI examples are shown in Figs.3 to 10.

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GUI example, Telemetry list viewFig.3

GUI example, Telemetry graph viewFig.5

GUI example, Telemetry time seriesview

Fig.4

6 Integration of dedicated unitinto the major shared unit

Interface specifications between the dedi-cated unit and the major shared unit werecoordinated for each dedicated unit individual-ly, since the number of dedicated units in theCRL T&C system is few. No general-purposeinterface specifications were defined.

Fundamental interfaces in the currentimplementation are as follows.Telemetry processing

In telemetry processing, from the needfor real-time operations, and the need forthe capability to display telemetriesprocessed by the dedicated unit togetherwith other telemetries in the same window,a processing program of the dedicated unitwas built into the major shared unit andmade to work on any terminal. Morespecifically, a Java class created for the

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GUI example, Telemetry block dia-gram view 1

Fig.6

GUI example, Telemetry block dia-gram view 2

Fig.7

GUI example, Command transmittingwindow

Fig.8

GUI example, SOP defining windowFig.9

GUI example, Telemetry databaseediting window

Fig.10

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dedicated unit was included in the majorshared unit. Since there are some dynamicalterations of the diagrams that representthe configuration of equipment accordingto the command transmission, the files ofthe block diagram created by the dedicatedunit in each case are accessed via file shar-ing.

Command processingAny command transmitted by the dedi-

cated unit is a packet command. Com-mands registered in advance as SOPs, i.e.,commands are previously constructed andfiled, are transmitted by normal SOP exe-cution. Command construction is execut-ed on the dedicated unit, and commandsare given to the major shared unit by filesharing.

7 Afterword

Development of the CRL T&C system wascarried out by placing orders to manufacturersin piecemeal fashion corresponding to areas ofdevelopment: design work; software manufac-turing work based design; and database con-struction tool manufacturing work. In startingthe design work, the author formulated guide-lines of the configuration corresponding to abasic design. Manufacturers then gave shapethereto in terms of system implementation andmodified the basic design according to its con-tent. The software manufacturing was fin-ished by fiscal 2002.

Hardware, such as host PCs, and OS wereprepared by the CRL; implementation of theT&C system for communication experimentsand for time comparison experiments (i.e.,installation of the software and database con-struction) are being undertaken with the sup-port of the manufacturers. Figs.11 and 12

show host equipment of the major shared unitfor communication experiments installed inthe Kashima Space Research Center.

On the other hand, CRL performed inter-face coordination alongside NASDA to deter-mine interface specifications with the NASDAsatellite control system in the early designstage. There was an option to borrow the soft-ware system from NASDA to ease interfacingwork, but it was finally decided due to the sys-tem scale and other factors to develop originalsystem software.

Henceforth, system test, adjustment, andtraining of operators are planned to proceed inaccordance with the ETS-VIII launch sched-ule. The interface test with the NASDA satel-lite control system is a major testing milestoneand is to be carried forward in close coopera-tion with NASDA.

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Photograph of T&C system for com-munication experiments 1

Fig.11

Photograph of T&C system for com-munication experiments 2

Fig.12

OHASHI Hajime

Senior Researcher, Space Data Trans-mission Group, Wireless Communica-tions Division

Satellite Communication Engineering