2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/5250Very long baseline interferometry (VLBI) provides the resolution needed to make precision measurements of a pulsar's parallax and proper motion. In making these measurements, the astronomer is faced with difficult calibration problems and a paucity of strong point-like calibrators that ultimately limit the accuracy of parallax measurements of even the brightest pulsars. A new technique to calibrate away the effects of the ionosphere, the dominant source of phase error at frequencies below 5 GHz, has led to the new measurements of nine pulsar parallaxes to 100 microarcsecond or better precision.6 pages, 2 figures, to appear in ASP Conf. Ser., Radio Pulsars, ed. M. Bailes, D. J. Nice, & S. E. Thorsett (proceedings of August 2002 meeting in Crete)Astrophysicstext