PHASE COMPENSATION EXPERIMENTS WITH THE PAIRED ANTENNAS METHOD

Several kinds of techniques are under development for effective correc tion of a tropospheric phase fluctuation in millimeter- and submillime ter-wave radio interferometry, including very long baseline interferom etry (VLBI), We report here the results of phase correction experiment s using a method called ''paired antennas method.'' In the method, pai rs of closely located antennas are used for obtaining the fringe phase s of both an observing source and an adjacent reference calibrator sim ultaneously, and the temporal variation of the obtained fringe phase o f the target source is corrected by using the calibrator phase. In cas es where the separation angle between the target source and the calibr ator is sufficiently small, the correction will be almost perfectly ma de. The experiments were carried out with the Nobeyama millimeter arra y (NMA) with a special emphasis on examining the separation angle depe ndence of the degree of the phase compensation. We simultaneously obse rved the Japanese Communication Satellite (CS) and a quasar 3C279 pass ing near the satellite at 19 GHz using four antennas of the NMA in ord er to measure the fluctuation of the difference in their fringe phases in dependence on the angular separation. The standard deviation of th e differential fringe phase estimated for 500-s time interval is reduc ed from 50 degrees-70 degrees to 10 degrees as the angular separation decreases from 20 degrees or greater to a few degrees. The results ind icate that the method is very useful for the correction of the troposp heric phase fluctuation in millimeter- and submillimeter-wave interfer ometry.