COMMAND AND DATA HANDLING

1. COMMAND AND DATA HANDLING Instructor: Roy C. Hsu Computer Science and Information Engineering Department National Chiayi University 10/30/2008

2. OUTLINE • Introduction • Command Systems • Telemetry Systems • Data Processing and Storage • Cases Study

3. INTRODUCTION • Command and Telemetry • providing information to and from the spacecraft, respectively • computer-based components in the spacecraft (S/C) and at terrestrial sites • commands are used to provide the info to change the state of the S/C subsystems and to set to S/C clock • telemetry subsystem collects and processes a variety of data to be transmitted from the S/C

4. INTRODUCTION (Cont.) • Data Processing and Handling • 3 major tasks on board • to help control and configure the S/C • to optimize the overall system performance • to process data for transmission • a major onboard processor and possibly multiple dedicated processors for various subsystems are used to enhance S/C performance and reliability. • ROM and RAM are used with RAM changeable through the command system • S/C data storage media: flash memory, SSR, etc • software written in machine, assembly, or high level language • I/O and other peripherals

5. COMMAND SYSTEMS • Purpose • to permit the spacecraft or its subsystem to be reconfigured in response to radio signals send up to the S/C from ground • Operation • receive the signals, • decide what they mean, • and then respond accordingly so that the desired reconfiguration takes place • The command system has a vital role in the overall operation of the S/C

6. GENERALIZED SPACECRAFT COMMAND SYSTEM Receiver/ Demodulator Command Decoder Command Logic Interface Circuitry Block Diagram of a generalized command system Receiver/Demodulator: amplify the signal captured, demodulate the command (cmd) message, deliver the encoded subcarrier signal message to the cmd decoder Command Decoder: decode the message to reproduce the original cmd message, which consists of a serial digital binary of 1s’ & 0s’ Command Logic: validate the cmd message, drive the I/F circuitry by executing the cmd Interface Circuitry: might be simple or complex functions

7. COMPLETE COMMAND SYSTEM Ground Support Equipment Modulation Radio Frequency Link Spacecraft Command System Block Diagram of a complete command system

8. SYSTEM REQUIREMENTS S/C MISSION S/C ORBIT/ TRAJECTORY GROUND STATION LINK ANALYSIS/COVERAGE COMMAND LOGIC

9. TELEMETRY SYSTEMS • Telemeter: to measure from a distance • Functions: to provide remote indication of what the desired measurements are • Telemetry data: • Status data - S/C resources, health, attitude, operation mode • Scientific data gathered by onboard sensor- magnetometers, thermometers, etc… • SpecificS/C orbit and timing data– used for guidance and navigation by ground, sea or air vehicles • Image data - captured by onboard camera • Other data - locations of other objects, relayed telemetry data from other satellites

10. SPACECRAFT TELEMETRY SYSTEM ACQUISITION Sensors Conditioners Selectors Converters PROCESSING Compressors Formatters Storage TRANSMISSION Encoder Modulator Transmitter Antenna Block Diagram of a spacecraft telemetry system Acquisition: The acquisition of data is accomplished using sensors, signal conditioners, data selectors and A/D converters. Processing: The data are processed in the telemetry system processor or in the smart sensor instrument’s resident processor. Transmission: as discussed in TT&C

11. TELEMETRY SYSTEM OF GROUND SEGMENT RECEIPT Antenna Receiver Demodulator Decoder PROCESSING De-compressor Translator Storage DELIVERY Display Printer Plotter Block Diagram of a ground segment telemetry system

12. SPACECRAFT DATA HANDLING • Spacecraft data processing and storage require the use of space-qualified microcomputers, memories, and interface devices. • Unlike the devices that are used in desk-top PC, S/C applications impose design constrains that are much more severe. • Low power dissipation, volume, and mass must be achieved without sacrificing overall performance. • S/C systems must exhibit excellent reliability and should be able to tolerate many kind of faults.

13. SPACECRAFT DATA HANDLING SYSTEM CENTRAL PROCESSING UNIT PROCESSOR DATA BUS MEMORY: ROM, RAM, Special- purpose MASS STORAGE INPUT/OUTPUT PORTS BUS INTERFACE SPACECRAFT DATA BUS

14. CENTRAL PROCESSING UNIT • One or more processing units have access to various kinds of memory, mass storage, and input/output devices • Job of the processing unit • execute the program that is stored in memory, interpret and execute commands received from the S/C command system. • maintain system status and health data (housekeeping data) and format the data for transmission to the S/C telemetry system.

15. CENTRAL PROCESSING UNIT (cont.) • The processing unit receives its instructions from a program stored in memory and communicates with its data sensors and other processors in the S/C through various kinds of I/O channels or over the S/C data bus. • The processing unit may elect to delegate some of its tasks to special purpose peripheral processors that then execute the delegated subtasks in parallel with the execution of its own tasks.

16. FLIGHT SOFTWARE DEVELOPMENT • Code development for embedded real-time processor using assembly and high-level language. • The program must be error-free for the S/C data handling system. • Employing computer science to design and implement the algorithms and data structure. • Applying software engineering approachto the design and maintenance of the software product.

17. FLIGHT SOFTWARE DEVELOPMENT (cont.) • The quality of the up-front conceptual design of the flight software will determine the success of software engineering. • The problem introduced early in the design phase will be the most expensive problem. • The costly problem is caused by correct implementation of a poor conceptual design, not by an incorrectly implementation of a good conceptual design.

18. OTHER DATA HANDLING COMPONENTS • Memory: Read-Only-Memory (ROM), Random-Access Memory (RAM), Flash Memory. • Mass Storage: disk, digital tape, solid state memory, magneto-optical disks, memory IC. • Input/Output: I/O Ports, direct memory access (DMA), multi-port memory, interrupts, timers, bus interface. • Fault Tolerance: radiation harness, single event upsets, CMOS latch-up, parity, error detection/correction, watchdog timer, etc… • Custom, Special-Purpose Peripherals: data acquisition, data compression, image processing. • Spacecraft Autonomy: the ability to monitor S/C internal functions and take appropriate actions without direct intervention from the ground.

19. ROCSAT-1 CASE STUDY • A low-earth orbiting (LEO) satellite jointly developed by TRW of U.S. with a resident team of NSPO engineers. • Launched on January 27, 1999 into an orbit of 600 kilometers altitude and 35 degrees inclination. • Three scientific research missions/Payloads: • ocean color imaging/OCI, • experiments on ionospheric plasma and electrodynamics /IPEI, • experiments using Ka-band (20-30 GHz) communication payloads/ECP.

20. ROCSAT-1 COMMAND AND TELEMETRY SYSTEM • S-band • Consultative Committee for Space Data Systems (CCSDS) Packet Telcommand and Telemetry • Uplink data rate: 2 kbps • Downlink data rate: 1.4 mbps • Data storage: 2 GB

21. ROCSAT-1 COMMAND SYSTEM 2039 MHZ 2Kbps NRZ-L SPECIAL COMMANDS BILEVEL TIE PCU RCVR ADE,GPS,PCUDDC,SAR,DIE DSE SERIAL OUTPUT CIRCUIT SOFTWARE BILEVEL MDE,OBC,PCU TDE,DDC RCVR ANA MDE 1553 OBC TIE,RIU OCI,IPEI

22. ROCSAT-1 Telemetry Processing Overview GPSE Spacecraft Subsystems Spacecraft 1553 BUS RF Assembly Transponder TIE OBC IPEI Science Data RS 422 Recorded / Playback Data OCI Science Data RS 422 Serial SSR RIU ECP Downlink FDF SDDCs TT&C Station MOC SSC Ground

23. ROCSAT-1 DATA HANDLING SYSTEM • On Board Computer（OBC）: 80C186 CPU • Real-time operation system: Versatile Real-Time eXecutive (VRTX32/86), a real-time multi-tasking OS • Employing software engineering approach for the development of the flight software. • A real-time embedded system

24. ROCSAT-1 FLIGHT SOFTWARE • Software executes on an 80C186 OBC • No floating point co-processor • Written in C, some assembly required • Multi-tasking implementation • Software is organized into 8 CSCs

25. ROCSAT-1 FLIGHT SOFTWARE (cont.) • ACS = Attitude Deter. & Control Subsystem • EPD = Electrical & Power Distribution • CCI = Command and Communication Interface • SCP = Stored Command Processor • CDS = Command Dispatcher Subsystem • UTL = Utilities • DAQ = Data Acquisition • EXE = Executive

26. ROCSAT-1 FLIGHT SOFTWARE FUNCTIONS • EPD CSC • - Controls battery charging and maintain battery state of charge data. • - Detects anomalous power subsystem behavior • - Collects sensor data for solar array on ground command • - Uses ground station control for long term operation >> Battery trending and trickle charge timing monitoring • EXE CSC • - Creates tasks and determines initial spacecraft operational mode • - Provides multitasking and floating point software routines • - Memory scrubs and memory uploads as background processing

27. ROCSAT-1 FLIGHT SOFTWARE FUNCTIONS (cont.) • SCP CSC • - Inserts validated RTCS uploads and ATC uploads into memory • - Manages the RTCS and ATC areas: >> Cancel ATC, Execute, RTCS, Inhibit RTCS, Enable RTCS, Delete RTCS, Cancel RTCS • - Schedules the execution of each command in a RTCS by assignment of an absolute execution time • UTL CSC • - Common routines; delay, crc, error handling, etc. • - Hardware interface routines; serial, analog, GPS, GSE, 1553B • - Interrupt Service Routines (ISR)

28. ROCSAT-1 FLIGHT SOFTWARE FUNCTIONS (cont.) • CDS CSC - Execute each command in the Command Allocation Document • DAQ CSC • - Reads sensor data from the hardware • - Formats state of health data into 1 of 3 Telemetry formats >> Normal >> Programmable >> Dump • - 32 minor frames (0-31) per major frame, 212 bytes per minor frame • - 1, 2, and 4 byte quantities supported

29. ROCSAT-1 FLIGHT SOFTWARE FUNCTIONS (cont.) • ADCS CSC • - Processes data from the gyros, earth sensor assemblies, fine sun sensors, coarse sun sensor assemblies, and three axis magnetometer • - Generates commands for the scan wheels, reaction wheels, thrusters, and torque rods. • - Controls the orientation of the spacecraft in all of its operational modes. • - Performs ephemeris determination based on the onboard clock and periodic uploads of orbital elements from the ground • CCI CSC • - Validates and processes command frames from the CUB • - Validates command type field, ATCs, and RTCSs command frames before placing them into the CIB • - Validates real-time command frames • - Manages the CIB with special parameter commands “Clear CIB”, “Transfer CIB”, and “Restart CIB Load”.

30. FLIGHT SOFTWARE INITIALIZATION • Initialization -Disable interrupts -RAM initialization -Copy Flight Software from EEPROM to RAM -Resets the watchdog timer -Initializes hardware -Initializes Interrupt Vector Table (IVT) -Initializes VRTX -Creates the EXE task -Passes control to VRTX

31. INITIALIZATIONTOP LEVEL STRUCTURE Power_up/ Hardware Reset exe_bootup Software “Reset” Software Restart exe_restart exe_main utl_isr_load exe _vrtx_init VRTX

32. TASK STRUCTURE Priorities QTR=10 ONE=20 SCP=30 SXT=40 EXE=50 Startup Code QTR ONE SXT SCP EXE

33. TASK CONTROL DIAGRAM SP_TASK_INIT_EF* EXE SXT SP_SCHEDULE_EF SP_SCHEDULE_EF SP_QTR_IEF QTR ISR SP_SCHEDULE_EF QTR C U B ONE Uplink ISR SP_ATC_EF SP_RTCS_EF SP_ALARM_EF SP_ONE_IEF SCP SP_SCHEDULE_EF ONE ISR CUB-Command Uplink Buffer *-set by QTR,ONE,SXT,SCP

34. COMMAND INPUT DATA FLOW Uplink interrupt OUB CIRCULAR BUFFER CCSDS codeblock Codeblock Status table Uplink ISR Command frames CCSDS Transfer Frame processing QTR task CCI_MAIN CDS Library Real-time command ATC RTCS KPD,code and data upload CCI_COMMAND_ PROCESSING CCI Library

35. COMMAND EXECUTION DATA FLOW real_time CMD CUB SP_rt_ Command_ Jump_table CDS Library ccl_real_time_ command Real_time CMD cci_command_ uploads ATC CMD cci_atc_ command_types CCI_ Comand_ Jump_ table cci_command_ processing RTCS CMD CLB cci_rtcs_load KPD upload cci_memory cci_kpd_load SP_UPDATE_RTCS_EF Code&data upload SP_update_ Rtcs_queue cci_code_ and_data_upload RTCS SCP Task Manage CIB SP_schedule_ atc_queue ACT cci_manage_cib SP_SCHEDULE_ATC_EF EXE Task