D. S. MacMillan 16-April-2008 Modeling Phase and Cable Cal for ONSALA60 Dan MacMillan NVI/NASA/GSFC Per Bjerkeli Chalmers University, Sweden Modeling Phase and Cable Cal for ONSALA60 Dan MacMillan NVI/NASA/GSFC Per Bjerkeli Chalmers University, Sweden
D. S. MacMillan 16-April-2008 Overview The RDV experiments (6 per year) use the 10 station VLBA network plus 9-10 of our geodetic antennas. Currently phase cal is not available at the correlator for the non-VLBA antenna Dependence of cable delays on the direction that an antenna is observing => Bias in estimated station coordinates The cable wrapping at Onsala causes cable stretching that varies ~linearly with azimuth => mm bias if cable cal is applied with no phasecal.
D. S. MacMillan 16-April-2008 Onsala Phasecal Group and Cable Delay Phasecal group delay ( sec) vs. azimuth from a year of Europe sessions Cable delay ( sec) vs. azimuth from a year of Europe sessions
D. S. MacMillan 16-April-2008 BaselineNo Cable Applied Model 1Model 2 (mm) Gilcreek - Onsala Medicina - Onsala NyAlesund - Onsala Wettzell - Onsala Matera - Onsala Hartrao - Onsala Bias of RDV Onsala Baseline Lengths (Relative to Trend of All Other Sessions) Model 1 : Phase Cal = 2 * Cable Cal Model 2 : Azimuth/Temperature dependent models for Phase Cal and Cable Cal
D. S. MacMillan 16-April-2008 Correcting the radio source group delay with the phase cal group delay will overcorrect by –τ pc. Cable cal correction = + τ pc If there is no phase cal then assume that the phase cal and IF cable delays are the same => Correction = - τ pc Instrumental group delay for the radio source Instrumental group delay for phase cal
D. S. MacMillan 16-April-2008 ( ϕ < π ) ( ϕ > π ) Phase Cal and Cable Cal Models A year of EUROPE sessions (Jan to Feb. 2002) were analyzed Cable cal and Phase cal were extracted and fit with functions of azimuth, temperature, and elevation where ϕ is azimuth and ε is elevation and T is temperature.
D. S. MacMillan 16-April-2008 a-coefficients for cable cal model as a function of temperature. a1 a2
D. S. MacMillan 16-April-2008 a-coefficients for phase cal model as a function of temperature. a1 a2