VLBI Antenna Calibration via GPS

We propose to investigate and develop an inexpensive system to determine: 1)VLBI antenna properties such as axis-offset, non-intersection of axis and antenna reference point; 2) Gravitational and/or Thermal deformation; 3) The eccentricity vector from the VLBI antenna to nearby GPS receivers. The proposed system involves using several GPS receivers in close proximity driven by a common clock. Because of their proximity, atmosphere and ionosphere errors are common, and vanish when we take the difference of measurements from different receivers to a common a satellite. Satellite clock errors also vanish in this difference. Since the receivers use a common clock, receiver clock error also vanishes. The remaining error source is GPS multipath which can be mitigated.