Correcting Radio Astronomy Interferometry Observations for Ionospheric Refraction,
NETHERLANDS FOUNDATION FOR RADIO ASTRONOMY DWINGELOO
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Radio astronomical observations with local interferometers and very long baseline interferometers VLSI are affected by atmospheric i.e. tropospheric and ionospheric refraction. A correction procedure for ionospheric refraction for radio astronomy interferometry is reviewed in the present paper. This correction is applied to observations made with the Westerbork Synthesis Radio Telescope WSRT. The method used for WSRT observations can also be used to correct VLBI observations for ionospheric refraction. If networks of ionosonde and satellite observing stations operate during the astronomical VLBI observations, pathlength corrections ranging from several wavelengths to a fraction of a wavelength are possible, provided the geographical distribution of these stations is similar the VLBI network. The possibilities of this procedure are compared with the results derived by e.g. dual frequency VLBI observations.