PHASE COMPENSATION EXPERIMENTS WITH THE PAIRED ANTENNAS METHOD - 2 - MILLIMETER-WAVE FRINGE CORRECTION USING CENTIMETER-WAVE REFERENCE

An experiment for compensating interferometer phase fluctuations due t o the turbulent troposphere was conducted with the paired antennas met hod (PAM) using different sky frequencies for a target and reference s ource. A celestial source 3C279 was observed at 146.81 GHz with the No beyama millimeter array (NMA), while a geostationary satellite was obs erved as a reference source at 19.45 GHz with commercially available a ntennas. Each of the antennas was installed near one of the NMA antenn as, thus giving us 10 pairs of nearly parallel baselines up to 316 m. Large fluctuations in the interferometer phase of 3C279 were mostly el iminated on almost all baselines by subtracting the reference phase mu ltiplied by a ratio of the observing frequencies. The standard deviati ons of the compensated interferometer phase were under the level of 20 degrees where the angular separation between the two sources was with in 2 degrees, while those of the original phase were typically at the level of 40 degrees-50 degrees. The phase compensation was much improv ed to the level of the differential excess path length of 0.06-mm rms (11 degrees at 146.81 GHz) in inserting a time lag proportional to the separation angle to the reference phase time series. These results ha ve practical significance for the millimeter- or submillimeter-wave in terferometry because there is rarely a suitable reference source in th e vicinity of scientifically interesting sources at such high frequenc ies. The present experiment shows that it is quite effective in the PA M to use the reference phase at centimeter-wave for compensating the m illimeter-wave phase for future large millimeter-wave arrays.