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VLBI2010 Reference antenna for antenna deformations and site ties

Explore using a small reference antenna for VLBI2010 antenna deformations and GNSS site ties. This innovative approach utilizes connected element interferometry, observation of GNSS satellites, and intersection of antenna axes for reference point determination. Key questions addressed relate to correlated sources and GPS multipath.

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VLBI2010 Reference antenna for antenna deformations and site ties

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  1. VLBI2010 Reference antenna for antenna deformations and site ties East Coast Geodetic VLBI Meeting 23-24 Feb, 2011, Haystack Observatory Bill Petrachenko

  2. Using a small reference antenna for antenna deformations and site ties • Use connected element interferometry • to a small nearby antenna to measure • the “effective” reference point of the • VLBI2010 antenna • and to measure the effect of • VLBI2010 antenna deformations Observe GNSS satellites with the same small antenna and measure the “effective” reference point of the GNSS antenna The intersection of axes of the small antenna becomes the reference point for both VLBI & GPS and ties the techniques VLBI2010 antenna Small reference antenna GPS antenna

  3. Question 1: Are there enough strong sources to correlated with a small reference antenna? • System parameters • Ref. antenna: D = 2-, 2.5, or 3-m; eff = 0.5; Tsys = 80-K • Centre freq = 8.5-GHz • BW = 1-GHz • TINT = 60-s • Single-polarization • SNRmin = 10 • Sources selected from the Bordeaux Image Gallery • 834 candidate VLBI sources • Each oberved 1 to ~40 times in S-, X-, K-, and/or Q-band • Parameters in the data base • Total flux (ST) • Median correlated flux (Sm) over UV-plane • Delay error, median for UV-plane • I used median values for ensemble of sessions observed

  4. Number of sources available for a 2-, 2.5-, or 3-m reference antenna correlated with a 12-m VLBI2010 antenna 2-m 2.5-m 3-m

  5. Question 2: Is GPS multipath small enough using a small parabolic reference antenna? • Worst case assumptions • Multipath reflector is horizontal with 100% reflection coefficient • Sidelobe gain for the ref. antenna is according to the ITU equation: Gi = 32-25*log10(θ) • The multipath signal phase is offset by 90 deg from the direct signal.

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