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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
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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
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Rationale for new development
Aging antennas and electronics RFI Better accuracy needed for TRF (~1 mm) May 7, 2007 VLBI2010 Prototype/Review
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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
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VLBI2010 Prototype/Review
Outline VLBI2010 Data acquisition Calibration Correlator Observable processing May 7, 2007 VLBI2010 Prototype/Review
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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
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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
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Broadband Delay Frequencies
May 7, 2007 VLBI2010 Prototype/Review
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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
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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
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Data Acquisition Upgrade Path
Long term (≥2010) Broadband at optimum frequencies Avoid RFI Burst mode May 7, 2007 VLBI2010 Prototype/Review
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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
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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
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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
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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
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VLBI2010 Prototype/Review
9/6/2018 May 7, 2007 VLBI2010 Prototype/Review
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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
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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
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VLBI2010 Prototype/Review
BBD S/X 4 Gb/s test May 7, 2007 VLBI2010 Prototype/Review
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VLBI2010 Prototype/Review
BBD S/X 4 Gb/s test May 7, 2007 VLBI2010 Prototype/Review
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VLBI2010 Prototype/Review
Patriot 12 m Antenna May 7, 2007 VLBI2010 Prototype/Review
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