1. Geodetic VLBI activities in China
Fengchun Shu
Shanghai Astronomical Observatory, CAS
Dec. 5, 2012, Saint-Petersburg

2. Outline Early history of geodetic VLBI in China
Related VLBI technique development
Shanghai Correlator
CDAS digital backend
Geodetic VLBI observing program
CMONOC project
IVS sessions
Outlook for the future development

3. Early history of geodetic VLBI in China
1985&1986
Shanghai(6m)—Kashima(26m) (X-band only) geodetic VLBI experiments
April, 1988
Seshan25 began to participate in international geodetic VLBI experiments, such as:
CDP and DOSE/NASA
Chinese-Japanese Joint VLBI Experiments
Chinese-German geodetic VLBI Cooperative Project
March, 1994
Nanshan(25m), Urumqi began to participate in international geodetic VLBI experiments

4. Shanghai-Kashima Geodetic VLBI Experiments(X-band only, 1985/86)
Shanghai(6m)

5. Seshan25 station
Installation completed 1987, and became operational since 1988

6. First Geodetic VLBI Experiment of Seshan25
S/X-band
Gilcreek
Kashima
Sheshan
Kauai

7. Urumqi station - Nanshan 25m antenna
Opening Ceremony was held in October 1994

8. First Geodetic VLBI Experiment of Urumqi
Gilcreek
Nanshan
Kokee
Sheshan
DSS45

9. Outline Early history of geodetic VLBI in China
Related VLBI technique development
Shanghai Correlator
CDAS
Geodetic VLBI observing program
CMONOC project
IVS sessions
Outlook for future development

10. Shanghai Correlator Operational for ChangE-1 Lunar project since 2006
Hardware platform
SMP (Symmetric Multiple Processor) commercial PC server
Software platform:
Linux Operation System
Correlation speed:
40Mbps/station, 4 stations
Special correlation ability
Data latency < 3 min
Fast fringe search and satellite delay model reconstruction

11. Specifications of Shanghai correlator
Architecture
station based FX type
Correlation station number
1~4
IF number
1~16
Frequency channel
32~4096/IF
Integration period
0.1~60 second
Input data format
Mark5A
Output data format
CVN
Fringe search
2-4 stations
Correlation speed
40Mbps/station (4 stations, 1024/IF)
Data latency
< 3 minutes
PCAL detection
Yes

12. Block diagram
NFS: Network File System

13. Shanghai correlator upgrade for geodesy
correlator control system
SKED/SCHED/SATSKD interface
Scan-based processing
MK5B playback capability
observable extraction
flag, fringe fit, manual phase calibration, bandwidth synthesis, NGS format output
Graphic display, data quality statistic

14. Software architecture

15. Correlation system hardware

16. New platform for correlation
Blade Cluster
6 x Blade Server
Blade Configuration: 2xIntel Xeon 5570 (2.93G),
12G DDR3 Memory,
10GbE NIC with TOE && RDMA
Storage
3x10TB Raid,10GbE NIC

17. MARK5 system
Mark5 data playback disk modules, 8TBytes

18. Performance evaluation of the correlator
3 stations:
~800Mbps
5 stations:
~400Mbps
10 stations:
~140Mbps

20. CDAS development
2007/6: the project initiated, meeting the requirement from 2 new VLBI stations (Kunming+ Beijing)
2010/4: deployment of 16 channels CDAS at 4 Chinese stations
2010/7: CDAS+MK5B(+)+eVLBI setup for satellite tracking
2010/8: Seshan25 participated in IVS-R1445 with the use of CDAS, the project concluded

21. Diagram of CDAS

22. CDAS 16 channels Platform (digital part)
4 IFs input
512MHz/IF
16 channels output
VSI-H interface
1/2 bit output

23. CDAS Poly-Phase Platform
1 U Box
One main Board
2x512Mhz IF input
1x16x32MHz output with VSI-H
2x16x32MHz output with 10GE
(in developing)

24. Outline Early history of geodetic VLBI in China
Related VLBI technique development
Shanghai Correlator
CDAS
Geodetic VLBI observing program
CMONOC project
IVS sessions
Outlook for future development

25. CMONOC project
the National Key Scientific Infrastructure Project --- Crustal Movement Observation Network of China
CMONOC-1
CMONOC-2
Construction period
1998～2000
2008～2010
Permanent GNSS stations 27
260
Other GNSS sites
1000
2000
SLR stations 5 7
Domestic VLBI obs. No
8 sessions/year

26. CMONOC-2: fiducial network stations

27. CMONOC-2: regional network stations

28. Goals of VLBI in CMONOC-2
Establishing an operational geodetic VLBI observing system
Full functional system
Full compatible with international VLBI community
Operational in stand-alone mode with Chinese domestic stations
Routine service with product quality data
Performing regular geodetic VLBI observations
Connection between global reference frame and Chinese regional network.

29. Chinese geodetic VLBI observing system

30. Distribution of Chinese VLBI Network

31. Geodetic observations for CMONOC project
Observing mode
128(data rate)-8(channel)-1(bit)
Observing sources
~35 sources from ~80
~65 sources from ~100
Observing sessions
6~12 on annual basis
Lower priority than satellite tracking/IVS/EVN sessions

32. Geodetic observations in IVS
R1、RDV、INT3
Participated with Seshan25 only
Participate in IVS-INT3 sessions as a backup station since April 2011
300Mbps to Bonn Correlator via Tein3 circuit
T2、APSG
Participated with Seshan25, Kunming and Urumqi

33. Kunming station January, 2011 July, 2011
Began to participate in the domestic geodetic observations with the use of CDAS
July, 2011
Began to participate in IVS-T2 and IVS-APSG sessions with CDAS
To get more precise station coordinates on global scale.
To further validate the performance of CDAS in geodetic observations.

34. Urumqi station
New S/X feed installed at Urumqi with wider frequency coverage: 8.0～9.0GHz
Ready to participate in IVS-R1/R4 sessions next year

35. Outline Early history of geodetic VLBI in China
Related VLBI technique development
Shanghai Correlator
CDAS
Geodetic VLBI observing program
CMONOC project
IVS sessions
Outlook for future development

36. CDAS future development
Performance improvement on 32MHz bandwidth based on geodetic test obs.
Better delay alignment among different BBC channels
Better Field System support
VDIF interface

37. Shanghai Correlator short term Mid-term Long term
Support the operation of CVN
Support the application of CVN in satellite tracking and radio astrometry
Mid-term
Improve e-VLBI capability of Chinese stations participating in international VLBI
Provide domestic geodetic results to IVS data center
Support data correlation of specific IVS sessions
Long term
Support data correlation of VLBI2010 observing sessions

38. VGOS - VLBI2010 Global Observing System
Plans have been put forward to construct at least 2 antennas in China, meeting the requirement of IVS2010.
A few candidate sites have been identified.
Collocated with SLR technique
Less RFI
Better sites distribution from global view

39. Candidate GGOS sites

40. Thank you!

41. NEW Receivers (2012)

42. Seshan25 station April, 2010 April, 2011
VLBA4 analog system was upgraded with VSI interface
CDAS was installed for the domestic observations
Mark5B+ recorder
April, 2011
Participate in IVS-INT3 sessions as a backup station
300Mbps to Bonn Correlator via Tein3 circuit
Contribution more to IVS by rapid UT1 measurement

43. Chinese VLBI sites in ITRF
C- Name DOMES-- CDP- Comments/description
cc nnnnnnnn ssssstmmm mmmm
Km KUNMING S m antenna at Kunming
Sg SHANGHAI 21605S m at Shanghai
Sh SESHAN S Shanghai
Ur URUMQI S Urumqi

44. IVS UT1 intensive observing stations