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

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

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

CVN Geography, 2003 KUNMIN - SESHAN URUMQI - KUNMIN URUMQI - SESHAN Satellite Observations

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

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

Satellite Fringe Searcher Interface

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 ,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

Fringe check Fringe check Fringe of satellite telemetry signals

Find the UR station local oscillator frequency shift

Test formatter Delay jitter

Delay of satellite TC-1(launching phase)

DOD of TC-1(launching phase)

Satellite Spin effect of the DOD

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

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

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

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)

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

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

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

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

CVN geography for Chinese lunar “Chang-E” project

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

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

Chang-E Software correlator system

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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)

Thank you very much