1. Next Generation Workshop Chinese VLBI Software Correlator Development and its Applications Zheng Weimin, Yang Yan, Zhang Dong, Chen Zhong, Shu Fengchun, Zhang Xiuzhong Shanghai Astronomical Observatory, Chinese Academy of Sciences 2006,06,28

2. 1. First Chinese software correlator: Satellite Fringe Searcher 2. CVN prototype software correlator 3. Quasi-realtime software correlator for Chinese Lunar project 4. Future plan 5. Conclusions Outline

3. 1.Satellite Fringe Searcher --First Chinese VLBI software correlator Experiment of track a geostationary satellite, 2003 CVN (Chinese VLBI Network) harddisk record/playback system(By Shanghai Observatory)CVNharddisk record/playback system 2-station hardware correlator could not find fringe? Attempt the software method

4. CVN Geography, 2003 KUNMIN - SESHAN25 1920. URUMQI - KUNMIN 2477. URUMQI - SESHAN25 3249. Satellite Observations

5. CVN harddisk system Record terminal CVN system: A VLBI harddisk system based on PC/Linux

6. Satellite Fringe Searcher 1 baseline, 1 IF correlator Hybrid architecture: XF and FX Specially for satellite downlink telemetry(TM) signals fringe search & correlation Function:VLBI correlation and post-correlation Produce delay and DOD (Differential One-Way Doppler )—delayrate Characteristic: Does NOT need a priori correlation delay model Matlab version

7. Satellite Fringe Searcher Interface

8. Satellite Fringe Searcher Applications 1.Fringe check through satellite telemetry(TM) signalsFringe check Station performance check Self-developed formatter check 2.Hardware correlator model guider and checker Produce Delay & Delay rate of satellite, more accurate than the prior modelDelay & Delay rate 3. Study the satellite orbit determination method by VLBI CVN 3-station tracked satellite TC-1 2004,7,27~29 Satellite Orbit: 550km perigee, 78000km apogee, 28.5 degree inclination Data processed by SFS correlator Chinese first satellite orbit determination experiment using VLBI. 4.e-VLBI experiment data correlatinge-VLBI experiment

9. Fringe check Fringe check Fringe of satellite telemetry signals

10. Find the UR station local oscillator frequency shift

11. Test formatter Delay jitter

12. Delay of satellite TC-1(launching phase)

13. DOD of TC-1(launching phase)

14. Satellite Spin effect of the DOD

15. Hardware correlator following the results of the software correlator results to get the fringes

16. 2003,5 e-VLBI data transmit experiment (FTP) of CVN

17. 2. CVN prototype software correlator Purpose: Process both quasar & satellite observation data Debug tool for CVN hardware correlator Started from 2004 First version, Matlab on Windows OS Final version, c language on linux OS

18. Specifications Architecture: FX 3 stations 1 IF ×32~4096 Channels / IF Data format: Mark4 recorded by CVN harddisk system Output format: self-defined visibility & self-spectra Correlation speed: 5MSample/s/station, 1bit/Sample, 1024Channel/IF (one Pentium 4 PC, 3.2GHz)

19. Block Diagram of CVN software correlator “FX” correlator model and Signal transformation ISTC: Integer Sample Time Correction FFT: Fast Fourier Transform FSTC: Fractural Sample Time Correlation MAC: Multiply-accumulate

20. Applications In operation: 2004~2006 Study the VLBI usage in the Chinese Lunar exploration project – Chang-E(CE-1) Processed much CVN observation data, for the analysis of DELTA-DOR: Chinese earth satellites :TC-1, etc. ESA SMART1 lunar spacecraft Processed the data of the Chinese first VLBI joint track TC-1 experiment, March, 2005 Debug tool of the CVN hardware correlator (under developing) Station fringe checker

21. SMART-1 O-C delay/delayrate compared with ESA orbit SMART-1 O-C delay/delayrate compared with ESA orbit Delayrate O-C Baseline SH-UR SH-KM UR-KM Delay O-C Baseline SH-UR SH-KM UR-KM

22. 3. Chang-E software correlator for Chinese Lunar project Chang-E lunar spacecraft will be launched in 2007 Chang-E software correlator design target:  2 working modes: Quasi-realtime, Non-realtime  Satellite fringe search and PCAL (Phase Calibration signal) abstraction abilities  4station, 8 IF  Processing rate, 16Msps/station, quasi-realtime mode  Backup of hardware correlator

23. CVN geography for Chinese lunar “Chang-E” project

24. CVN Configuration, 2006 4 stations: 2×25m + 50m + 40m Fiber link between stations VLBI center at Shanghai Observatory

25. CVN Topology Beijing Quidway S6506R VLBI center at Shanghai Observatory Data Server Firewall Secpath100F R Network Administrator Urumqi R R Kunming R Shanghai Quidway NE20

26. Chang-E Software correlator system

27. Chang-E software correlator system block diagram Function: VLBI correlation, fringe search, PCAL abstraction

28. Software correlator working platform Constructed by COTS component; Hardware platform: SMP (Symmetrical Multi Processing) PC server: HP585, Dawning4380 CPU:4 dual core AMD Opteron 875, 2.2GHz Software platform: Redhat Enterprise version

29. quasi-realtime mode No. 1 PC server: Software correlator No. 2 PC server: Fringe searcher & PCAL for software correlator No. 3 PC server: Fringe searcher & PCAL for hardware correlator

30. Specifications 4 stations FX architecture 8 IF ×64~4096 Channels / IF Data format: Mark5 Output format:self-defined Quasi realtime ability: Data input & output delay: < 4 minutes Correlating speed: 40Msps/station,4 station 1bit/Sample,1024Channel/IF (one PC server) portable, flexible, expandable to 10 stationsexpandable to 10 stations

31. Running on one HP585 PC server Testing data format: Mark5, 4IF/station, 4Msps/IF, 1bit/sample 10-station software correlator processing speed vs station number

32. Non-realtime mode 3 PC servers constitute a 4-station software correlator pipeline: speed: 120Msps/station, 8 IF ×64 Channels / IF

33. Applications(1) Test the performance of the new CVN stations ( Beijing & Kunming) and help to debug station system Get the first fringe of SH-BJ baseline, 2006,05,08fringe of SH-BJ baseline Get the first fringe of SH-KM baseline, 2006,05,15fringe of SH-KM baseline Debug tool of hardware correlator

34. 2006,05,08, First SH-BJ fringe of geostationary satellite

35. 2006,05,17, First SH-KM fringe of SMART1

36. BJ-KM UR-KMUR-BJSH-UR SH-KM SH-BJ First 4-station fringes in quasi rear-time mode Source SMART1 ， 2006,05,17 First 4-station fringes in quasi rear-time mode Source SMART1 ， 2006,05,17

37. Applications(2) Chinese first VLBI joint orbit determination experiment of SMART1 (lunar spacecraft), 2006,5,29~6,1 Chang-E software correlator successfully processed all VLBI data 2-stage experiment: 1st stage: 4 days real-time observation of SMART1& quasar, 2006,5,29~6,1, 15 hours observation / day Observing mode: S-band, narrow band, 2 IF, 2MHz bandwidth/IF, 1bit/sample Total data rate 8Mbps/station

38. Applications(3) Successful test fast satellite fringe search and delay model reconstruction ability Fringe searcher stopFringe searcher open

39. Applications(4) 2nd experiment stage: 24 hours quasar & SMART1 observation, 2006,6,2. 1. Geodetic experiment, accurate position determination of Beijing & Kunming station 2. High accurate DELTA-DOR experiment Observing mode: S+X band,wide band, 8IF, 8MHz bandwidth /IF, 1bit/sample 4096 channels/IF (SMART1) 64 channels/ IF(Quasar) Total data rate, 128Mbps/station  Software correlator played an import role in this experiment

40. 5-day orbit positioning O-C result Left:delay Right:delay rate 2006,5,29~6,2 5,295,30 5,31 6,16,2

41. 5-day angular positioning O-C result Up:Azimuth angle Down:Pitching angle 2006,5,29~6,2 5,29 5,305,31 6,16,2

42. 4. Future Plan Fulfill Chang-E software correlator Accelerate correlation speed using new structure: single PC server ⇒ PC server cluster

43. 5. Conclusions 1. Software correlator validates its value in the lunar spacecraft orbit determination. 2. Quite flexible and portable 3. Software correlator running on high performance SMP server (now) or small scale cluster(future) is very suitable for VLBI spacecraft navigation. 4. Software correlator working on large scale HPC will be a good candidate of the next generation high speed VLBI correlator for the radio astronomy and geodesy in the near future.

44. Conclusions General commercial computer will promote software correlator CMP & SMT CPU become popular. Cluster make HPC more popular and cheaper CMP: Chip Multi － Processing SMT: Simultaneous multithreading Cell processor:theoretical rate about 250GFLOPS, supported by Linux, IBM/Sony/Toshiba World first petaflops HPC “Braker” (2008), based on Linux-Opteron, Cray/AMD (Announced 2006,6)

45. Thank you very much