Transcript Next Generation Workshop Chinese VLBI Software Correlator

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
Outline
1.
2.
3.
4.
5.
First Chinese software correlator:
Satellite Fringe Searcher
CVN prototype software correlator
Quasi-realtime software correlator
for Chinese Lunar project
Future plan
Conclusions
1. Satellite Fringe Searcher
--First Chinese VLBI software correlator
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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
CVN Geography, 2003
Satellite Observations
KUNMIN - SESHAN25
1920.
URUMQI - KUNMIN
2477.
URUMQI - SESHAN25
3249.
CVN harddisk system
Record terminal
CVN system:
A VLBI
harddisk system
based on
PC/Linux
Satellite Fringe Searcher
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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
delay=1
Peak freq=263037.1094Hz(SH), Time=1365060000000(UTC)
1
SH-UR 1365060000000, Fr=991.6818¡À0.002764t+-0.37449
600
30
0.8
400
Phase (circle)
20
10
200
SH-UR
Power Spectrum Magnitude (dB)
40
0
0.6
0.4
0
-200
0
0.05
0.1
0.15
0.2
-10
0.25
0.3
0.35
0.4
0.45
0.2
Time
4
2.5
Frequency
3
3.5
x 10
5
Peak freq=264028.7912, Dopple freq shift=991.6818Hz(UR)
20
-10
-20
Cross Spectrum Magnitude (dB)
Cross Spectrum Phase Cross
(rad) Spectrum Phase (Degree)
-30
1.6
1.8
2
2.2
2.4
2.6
Frequency
2.8
3
3.2
3.4
x 10
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.4
0.3
0.2
0.1
2
0
-2
1.5
50
2
2.5
3
3.5
x 10
5
0
-50
1.5
2
2.5
Frequency
3
3.5
x 10
5
0
Lag
0.2
0.4
0.6
0.8
1
x 10
5
250
200
150
100
50
0
0
-2000
-1500
-1000
-500
0
Delayrate=991.6992(Hz)
500
1000
1500
2000
Phase (Degree)
60
50
40
0
0.05
0.1
0.15
0.2
0.25 0.3
Time(s)
0.4
0.45
0.5
0 -110.05
x 10
0.1
0.15
0.2
0.25
0.3 0.35 0.4
Delayrate=-0.079688Hz
Time(s)
0.45
0.5
1.5
Phase (rad)
Correlation Amplitude=4.0075e-011
20
1.6Lag=-1392,
1.8
2
2.2
2.4 Total
2.6Delay=-0.00696032941¡À1.4751e-009(s)
2.8
3
3.2
3.4
Iteration=2,
delay=2.5e-006(s),
5
4
x 10
-0.2
300
-1
Fr=-3.2941e-007f+0.23935,Time=1365060000000(UTC), Trk=10, sigma=3, Threshold Fr=-0.074884t+0.17116,Trk=10,sigma=3,Time=1365060000000(UTC),Total
value=-20
Delay Rate=991.60691¡À0.0035106Hz
80
70
40
-0.4
delay=2.5e-006(s)
5
60
-0.6
350
-2
Time
0
-0.8
0
-4
10
Correlation Amplitude=0.26181
Power Spectrum Magnitude (dB)
30
0
-1
2
Correlation Amplitude=327.1703
2
Phase (rad)
-20
1.5
0.35
1
0.5
6
4
2
0
-200
-150
-100
-50
0
50
Delayrate(Hz)
100
150
200
-0.5
0
Delay(s)
0.5
1
x 10
-3
Satellite Fringe Searcher Applications
1.
Fringe check through satellite telemetry(TM) signals
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 model
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 correlating
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
Nanshan
Sheshan
car
ISDN
car
Urmuchi
乌
Internet
Shanghai
Observatory
50Kb/s
2. CVN prototype software correlator
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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
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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
CVN
harddisk
ISTC
CVN
harddisk
ISTC
ISTC correlatorFringe
FFT transformation
FSTC
“FX”
model and Signal
Stopping
ISTC
Fringe
Stopping
SF12(ν)
SF11(ν)
SF22(ν)
FFT
ISTC: Integer Sample Time Correction
FFT: Fast Fourier Transform
FSTC: Fractural Sample Time Correlation
MAC: Multiply-accumulate
MAC
FSTC
Applications
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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
Delay
O-C
Baseline
SH-UR
Delayrate
O-C
Baseline
SH-UR
SH-KM
SH-KM
UR-KM
UR-KM
3. Chang-E software correlator for
Chinese Lunar project
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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, 2006
• 4 stations:
2×25m + 50m + 40m
• Fiber link between stations
• VLBI center at Shanghai Observatory
CVN Topology
Network
Administrator
Data Server
Quidway
S6506R
Firewall
Secpath100F
R
Quidway NE20
VLBI center at Shanghai
Observatory
Shanghai
R
Kunming
R
Beijing
R
Urumqi
Chang-E Software correlator system
Chang-E software correlator system
block diagram
PCAL
Calibration
Station
Shanghai
Fringe
searcher
Station
Urmuqi
Station
Beijing
Station
Kunming
Data receive &
Synchronization
NFS
Satellite delay
model
reconstruction
Correlator
control &
configure file
Output
Postprocess &
orbit
determination
Software
correlator
Function: VLBI correlation, fringe search, PCAL abstraction
Software correlator working platform
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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 stations
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
Non-realtime mode
3 PC servers constitute a 4-station software correlator pipeline:
speed: 120Msps/station,
8 IF ×64 Channels / IF
Data slice
S1
S2
S3
No.1 correlator
P1
P2
C1
S4
S5
S6
No.2 correlator
P3
S7
S8
P1
Playback No.1 data slice from all
station to No.1 software correlator
P5
Playback No.5 data slice from all
station to No.2 software correlator
P6
Playback No.6 data slice from all
station to No.3 software correlator
t
No.3 correlator
P4
P5
C3
C3
C3
C2
C2
C2
C1
C1
C4
P6
C1
No1 software correlator
process No.1 data slice
C5
No2 software correlator
process No.5 data slice
C6
No3 software correlator
process No.6 data slice
C6
C5
C5
C4
C4
t
Applications(1)
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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
2006,05,08, First SH-BJ fringe of
geostationary satellite
2006,05,17, First SH-KM fringe of
SMART1
First 4-station fringes in quasi rear-time mode
Source SMART1，2006,05,17
BJ-KM
SH-BJ
SH-KM
SH-UR
UR-BJ
UR-KM
Applications(2)
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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:
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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)
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Successful test fast satellite fringe search and delay
model reconstruction ability
Fringe searcher stop
Fringe searcher open
Applications(4)
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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: 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
5,29
5,30
5,31
Left:delay
Right:delay rate
2006,5,29~6,2
6,1
6,2
5-day angular positioning O-C result
5,29
5,30
5,31
Up:Azimuth angle
Down:Pitching angle
2006,5,29~6,2
6,1
6,2
4. Future Plan
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Fulfill Chang-E software correlator
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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
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General commercial computer will promote software
correlator
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CMP & SMT CPU become popular.
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Cluster make HPC more popular and cheaper
CMP:
Chip Multi－Processing
SMT:
Simultaneous multithreading
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Cell processor:theoretical rate about 250GFLOPS,
supported by Linux, IBM/Sony/Toshiba
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World first petaflops HPC “Braker” (2008), based on
Linux-Opteron,
Cray/AMD (Announced 2006,6)
Thank you very much