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Space-based Telemetry And Range Safety (STARS) Study
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  1. Space-based Telemetry And Range Safety (STARS) Study James Rash - GSFC Ed Criscuolo - CSC Keith Hogie - CSC Ron Parise - CSC

  2. Overview • Brief Description of STARS • Goals of the STARS IP Formatter • Key issues using standard HW for constant-rate Telemetry • Design and Development • Testing and Performance • Status 2004 Space Internet Workshop

  3. Space-based Telemetry and Range Safety • The STARS project is investigating the use of a reliable communication link between flight vehicles and satellites in order to support range operations such as those used in flight termination systems. • The project goals are to evaluate the system's reliability and performance, and to define a detailed design for the range system user that will reduce costs associated with dedicated groundstations. • Previous flights evaluated the reliability of satellite communication links with TDRSS • Next flights will incorporate the use of Internet Protocol (IP) for all downlink telemetry, and use a phased-array antenna to track TDRSS 2004 Space Internet Workshop

  4. Space-based Telemetry and Range Safety NASA Photo / Tony Landis 2004 Space Internet Workshop

  5. IP Formatter Goals • Transport all range user telemetry to groundsystem using standard Internet Protocols • Build on previous flight experience • Increase Flexibility, Reduce Costs • Off-The-Shelf PC-104 hardware • Open-Source operating-system (Linux 2.4.18) • Standard "C" code and scripting languages • Simplify Telemetry System • data capture • onboard logging • data transfer • Simplify Ground System • data routing and distribution • data logging 2004 Space Internet Workshop

  6. Key Issues Using Std Sync Serial H/W • Issue: Telemetry Framing • Sync Serial I/O cards are designed to handle discrete frames which may arrive asynchronously • PCM telemetry has continuous nonstop frames • Solution: • Use hardware to initially locate sync • Use back-to-back reads and software to flywheel & check sync • Use hardware to re-acquire sync if lost • Issue: Bit order • PCM telemetry is msb first • Communications industry (eg - hdlc/frame-relay) uses lsb first • Solution: • Use hi-speed software bit-reversal via table lookup 2004 Space Internet Workshop

  7. 153 byte telemetry data 3 byte (24 bit) Sync 153 byte telemetry data 3 byte (24 bit) Sync Telemetry Formats F-15 PCM Telemetry Stream 4 byte Seq # 8 byte timestamp IP Header (20) UDP Header (8) 156 byte telemetry frame UDP/IP Telemetry Packet 2004 Space Internet Workshop

  8. Telemetry Formats F-15 Telemetry Range Safety Telemetry Antenna Telemetry IP Formatter Status 10Kbit/sec PCM stream 124 byte frames w / 4 byte sync 1 Mbit/sec PCM stream 156 byte frames w / 3 byte sync Fixed size UDP packets with one 80-byte frame per packet. In IP Formatter Fixed size UDP packets with 1 frame per packet. Includes sync chars. Fixed size UDP packets with 1 frame per packet. Includes sync chars. Fixed size UDP packets with one 80-byte frame per packet. UDP packets with one ascii text line per packet. Out 2004 Space Internet Workshop

  9. IP Formatter System Architecture TDRS Phased Array Antenna Linux Console Character terminal 9600 baud N81 RS-232 DB-9 Network Int. IP- Ethernet RJ-45 Phased Array Control Antenna Control Ground Use Only Phased Array Status UDP/IP packets Ethernet DB-9 Network Console Port 40000 Video Audio CPU WAN Enerdyne Mux Net-Ser Formatter Output UDP/IP packets HDLC Sync serial RS-422 DB-37 F-15 Telem Char-Ser RS Telem IRIG-B timecode IRIG-B Coding PCB Conv Decode Ethernet GDDS Power PCM frames in bitstream Synced PCM frames Individual PCM frames in UDP/IP packets Coded Enerdyne muxed data bitstream 2004 Space Internet Workshop

  10. Packets addressed to specific UDP ports on FLAPS system 111.222.0.x Port 10000 F-15 PCM Data Receiver F-15 Data Port 20000 111.222.0.x Port 20000 IP Formatter Software Architecture R/S PCM Data Receiver UDPcapture #2 Range Safety Data Port 30000 111.222.0.x Port 30000 IP Formatter Status Gen UDPcapture #3 Timekeeper Port 40000 111.222.0.x Port 40000 UDPcapture #4 Time Stamps Phased Array Antenna Data Linux Operating System 2.4.18 kernel IP 111.222.0.x Ports10000, 20000, 30000, 40000 Minimal Kernel & File System Telemetry Sync Serial Driver Network HDLC Sync Serial Driver IRIG-B Driver Ethernet Driver Console Driver FLAPS RF System RS-422 RS-422 IRIG-B Ethernet RS-422 RS-422 RS-232 LAN Switch F-15 Range Safety IRIG Serial to Enerdyne Mux Test Access Phased Array Antenna Test Access Enerdyne Enerdyne Router 2004 Space Internet Workshop

  11. IP Formatter Development Bench Router PC/104 Proto Board PC/104 Cable Kit STARS IP Formatter PC/104 stack RS-422 Breakout Box Serial line to Enerdyne/Router 384MB Disks On Chip 2004 Space Internet Workshop

  12. Testing • "Gizmo" programmable telemetry generator used to simulate F-15 PCM telemetry • ParaScope serial line analyzer used to playback simulated Range Safety PCM telemetry • Custom data-generator program (provided by STARS) used to simulate Antenna telemetry data in UDP packets sent over ethernet • TrueTime 800 timecode generator for IRIG-B • Etherpeek network monitor SW used to monitor performance • Post-run analysis of captured telemetry on groundstation to determine packet loss rate 2004 Space Internet Workshop

  13. Testing F-15 Telem Gizmo RS Telem ParaScope CPU HDLCLink Ground System Router Net-Ser Antenna Sim Char-Ser IRIG-B Ethernet LAN Ethernet Power Timecode Generator IP Formatter PC/104 Stack EtherPeek 2004 Space Internet Workshop

  14. Performance • Test Conditions: • Full telemetry rates on all inputs (1.45 Mbits/sec aggregate) • HDLC output clock at 1.8 Mbits/sec (35 Kbits/sec headroom) • Onboard logging of all telemetry except F-15 • Results: • 40 - 50% CPU Utilization • All telemetry ingested with NO loss • Full output rate (average) with 1 - 2% packet loss • Attempted Mitigations: • DMA output driver: Reduced CPU usage, but loss unchanged • Reduced F-15 rate to 500 Kbits/sec: Loss reduced to 0% • Analysis: • Insufficient kernel buffer pool causing dropped packets on output 2004 Space Internet Workshop

  15. Status • IP Formatter delivered to STARS project onMarch 5, 2004 • Currently being integrated at the STARS facility at Dryden Flight Research Center (DFRC) 2004 Space Internet Workshop