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

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Next Generation WorkshopChinese VLBI Software
Correlator Development and its Applications
Zheng Weimin, Yang Yan, Zhang Dong, Chen Zhong,
Shu Fengchun, Zhang XiuzhongShanghai
Astronomical Observatory, Chinese Academy of
Sciences 2006,06,28
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Outline

• First Chinese software correlator
• Satellite Fringe Searcher
• CVN prototype software correlator
• Quasi-realtime software correlator
• for Chinese Lunar project
• Future plan
• Conclusions

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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)
• 2-station hardware correlator could not find
  fringe?
• Attempt the software method

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Satellite Observations
CVN Geography, 2003
KUNMIN - SESHAN25 1920. URUMQI - KUNMIN
2477. URUMQI - SESHAN25 3249.
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CVN harddisk systemRecord terminal
CVN system A VLBI harddisk system based on
PC/Linux
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Satellite Fringe Searcher

• 1 baseline, 1 IF correlator
• Hybrid architecture XF and FX
• Specially for satellite downlink telemetry(TM)
  signals fringe search correlation
• FunctionVLBI correlation and post-correlation
• Produce delay and DOD (Differential
  One-Way Doppler )delayrate
• Characteristic
• Does NOT need a priori correlation delay
  model
• Matlab version

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Satellite Fringe Searcher Interface
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Satellite Fringe Searcher Applications

• Fringe check through satellite telemetry(TM)
  signals
• Station performance check
• Self-developed formatter check
• Hardware correlator model guider and checker
• Produce Delay Delay rate of satellite,
  more accurate than the prior model
• Study the satellite orbit determination method
  by VLBI
• CVN 3-station tracked satellite TC-1
• 2004,7,2729
• Satellite Orbit 550km perigee,
  78000km apogee, 28.5 degree inclination
• Data processed by SFS correlator
• Chinese first satellite orbit
  determination experiment using VLBI.
• e-VLBI experiment data correlating

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Fringe check
Fringe of satellite telemetry signals
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Find the UR station local oscillator frequency
shift
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Test formatter
Delay jitter
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Delay of satellite TC-1(launching phase)
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DOD of TC-1(launching phase)
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Satellite Spin effect of the DOD
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Hardware correlator following the results of the
software correlator results to get the fringes
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2003,5 e-VLBI data transmit experiment (FTP) of
CVN
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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

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Specifications

• Architecture FX
• 3 stations
• 1 IF 324096 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)

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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
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Applications

• In operation 20042006
• 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

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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
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3. Chang-E software correlator forChinese 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

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CVN geography for Chinese lunar Chang-E project
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CVN Configuration, 2006

• 4 stations
• 225m 50m 40m
• Fiber link between stations
• VLBI center at Shanghai Observatory

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CVN Topology
Network Administrator
Data Server
Quidway S6506R
Firewall
Secpath100F
Quidway NE20
VLBI center at Shanghai Observatory
Shanghai
Beijing
Urumqi
Kunming
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Chang-E Software correlator system
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Chang-E software correlator system block diagram
Function VLBI correlation, fringe search, PCAL
abstraction
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Software correlator working platform

• Constructed by COTS component
• Hardware platform
• SMP (Symmetrical Multi Processing) PC
  server
• HP585, Dawning4380
• CPU4 dual core AMD Opteron 875, 2.2GHz
• Software platform
• Redhat Enterprise version

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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

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Specifications

• 4 stations
• FX architecture
• 8 IF 644096 Channels / IF
• Data format Mark5
• Output formatself-defined
• Quasi realtime ability
• Data input output delay lt 4 minutes
• Correlating speed 40Msps/station,4 station
  1bit/Sample,1024Channel/IF (one PC server)
• portable, flexible, expandable to 10 stations

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

• 3 PC servers constitute a 4-station
  software correlator pipeline
• speed 120Msps/station,
• 8 IF 64 Channels / IF

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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,
  2006,05,08
• Get the first fringe of SH-KM baseline,
  2006,05,15
• Debug tool of hardware correlator

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2006,05,08, First SH-BJ fringe of geostationary
satellite
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2006,05,17, First SH-KM fringe ofSMART1
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First 4-station fringes in quasi rear-time mode
Source SMART1,2006,05,17
BJ-KM
SH-KM
SH-BJ
UR-KM
UR-BJ
SH-UR
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Applications(2)

• Chinese first VLBI joint orbit determination
  experiment of SMART1 (lunar spacecraft),
• 2006,5,296,1
• Chang-E software correlator successfully
  processed all VLBI data
• 2-stage experiment
• 1st stage
• 4 days real-time observation of SMART1 quasar,
  2006,5,296,1, 15 hours observation / day
• Observing mode S-band, narrow band, 2 IF, 2MHz
  bandwidth/IF, 1bit/sample
• Total data rate 8Mbps/station

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Applications(3)

• Successful test fast satellite fringe search and
  delay model reconstruction ability

Fringe searcher stop
Fringe searcher open
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Applications(4)

• 2nd experiment stage
• 24 hours quasar SMART1 observation, 2006,6,2.
  
• Geodetic experiment, accurate position
  determination of Beijing Kunming station
• High accurate DELTA-DOR experiment
• Observing mode SX 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

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5-day orbit positioning O-C result
5,31
5,29
5,30
Leftdelay Rightdelay rate 2006,5,296,2
6,1
6,2
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5-day angular positioning O-C result
5,30
5,31
5,29
UpAzimuth angle DownPitching angle 2006,5,296,2
6,1
6,2
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4. Future Plan

• Fulfill Chang-E software correlator
• Accelerate correlation speed using new structure
  
• single PC server ? PC server cluster

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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.

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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 processortheoretical rate about 250GFLOPS,
  supported by Linux, IBM/Sony/Toshiba
• World first petaflops HPC Braker (2008), based
  on Linux-Opteron,
• Cray/AMD (Announced 2006,6)

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• Thank you very much