1. Haystack Geodesy Program and Technical Development
9/6/2018
Haystack Geodesy Program and Technical Development
Arthur Niell and Alan Whitney
MIT Haystack Observatory
May 7, 2007
VLBI2010 Prototype/Review

2. VLBI2010 Prototype/Review
Geodetic VLBI Program
Determine Terrestrial and Celestial Reference Frame and time variation
Measure Earth Orientation Parameters on all time scales down to about one hour
Regular observations on networks of ~8 antennas twice per week, 20 antennas every couple of months
Accuracy of TRF ~1 cm globally
May 7, 2007
VLBI2010 Prototype/Review

3. Rationale for new development
Aging antennas and electronics
RFI
Better accuracy needed for TRF (~1 mm)
May 7, 2007
VLBI2010 Prototype/Review

4. VLBI2010 Prototype/Review
Goals of VLBI2010 Project
Develop and demonstrate a new advanced geodetic VLBI system
Provide specifications and designs for the new system
May 7, 2007
VLBI2010 Prototype/Review

5. VLBI2010 Prototype/Review
Outline
VLBI2010
Data acquisition
Calibration
Correlator
Observable processing
May 7, 2007
VLBI2010 Prototype/Review

6. VLBI2010 Prototype/Review
VLBI Key Elements
Broadband delay (BBD)
Fast antennas
High data rates
Modern digital electronics and signal processing
Algorithm development
Correlator
May 7, 2007
VLBI2010 Prototype/Review

7. VLBI2010 Prototype/Review
VLBI2010 System
Technical approach
12m antenna
Broadband dual linearly-polarized feed 2 GHZ to ~15 GHz
Probably four bands (S,C,X,Ku)
Cooled MMIC low noise amplifiers
followed by multiple flexible LO systems
Digital Backends (DBEs)
8 Gb/s to 32 Gb/s data-capture rate
May 7, 2007
VLBI2010 Prototype/Review

8. Broadband Delay Frequencies
May 7, 2007
VLBI2010 Prototype/Review

9. VLBI2010 Prototype/Review
Observable
Phase delay across four bands (S,C,X,Ku)
4 psec delay precision with low SNR (~10 in each band)
May 7, 2007
VLBI2010 Prototype/Review

10. Data Acquisition Upgrade Path
Short term (~2008)
Replace Mark4 DAS and Mark5A at current sites with DBE and Mark5B: 1 Gbps
DBE and Mark5B+: S/X at 2 Gbps
Higher SNR
Medium term (~ )
S/X plus broadband mix of antennas
How to process mixture of circular and linear pol’n
May 7, 2007
VLBI2010 Prototype/Review

11. Data Acquisition Upgrade Path
Long term (≥2010)
Broadband at optimum frequencies
Avoid RFI
Burst mode
May 7, 2007
VLBI2010 Prototype/Review

12. VLBI2010 Prototype/Review
Calibration
Phase calibration
Inject inside Dewar?
Cable cal measurement system
Tsys measurement
Source structure corrections may be necessary for highest accuracy
60 scans/hr on sixteen antennas for 200 sources = several hundred u-v points per day per source several times per week at four frequencies
May 7, 2007
VLBI2010 Prototype/Review

13. VLBI2010 Prototype/Review
Correlation
How long can we use Mk4 correlator?
Playback limit is 1 Gbps
DBE/Mk5B at 1 Gbps for operations
DBE/Mk5B+ at 2 Gbps for operations at current observing density
Broadband delay probably only for testing
Need new correlator
16 – 32 stations
4 frequency bands
2 polarizations all cross-hands
4 Gbps playback rate
May 7, 2007
VLBI2010 Prototype/Review

14. Observable Processing (fourfit equivalent)
How to process broad band data for one delay
4 frequencies
2 polarizations
Source structure
Ionosphere
How to mix circular and linear
How (or whether) to use rates
May 7, 2007
VLBI2010 Prototype/Review

15. Status of VLBI2010 Development
Observations
4 Gbps S/X using Westford and MV-3 taken in March
1 DBE and 2 Mk5B+ at each site
8 Gbps using broadband (4 bands) planned for end of summer
2 DBEs and 4 Mk5B+ at each site
May 7, 2007
VLBI2010 Prototype/Review

16. VLBI2010 Prototype/Review
9/6/2018
May 7, 2007
VLBI2010 Prototype/Review

17. Accomplishments to date
Demonstration Hardware
Feeds and LNAs purchased
Local Oscillator (Up-Down Converter)
designed
parts ordered
Mark5B+’s operational
Digital backends operational
Sixteen 32-MHz channels
May 7, 2007
VLBI2010 Prototype/Review

18. Accomplishments to date
One 4 gigabit/sec S/X session observed
Westford-GGAO – existing feeds/front ends
Digital Back End – contiguous channels
Mk5B+’s
Simultaneous Mk4 for comparison
40 minutes on 3C84 – good phases
Six hours geodetic schedule – not analyzed yet
May 7, 2007
VLBI2010 Prototype/Review

19. VLBI2010 Prototype/Review
BBD S/X 4 Gb/s test
May 7, 2007
VLBI2010 Prototype/Review

20. VLBI2010 Prototype/Review
BBD S/X 4 Gb/s test
May 7, 2007
VLBI2010 Prototype/Review

21. VLBI2010 Prototype/Review
Patriot 12 m Antenna
May 7, 2007
VLBI2010 Prototype/Review