Very Long Baseline Interferometry

Ninth Synthesis Imaging Summer School, 15-22 June 2004 • Radio interferometry with unlimited baselines – High resolution – milliarcsecond (mas) or better – Baselines up to an Earth diameter for ground based VLBI – Can extend to space (HALCA) – Sources must have high brightness temperature • Traditionally uses no IF or LO link between antennas – Data recorded on tape or disk then shipped to correlator – Atomic clocks for time and frequency– usually hydrogen masers – Correlation occurs days to years after observing – Real time over fiber is an area of active development • Can use antennas built for other reasons • Not fundamentally different from linked interferometry WHAT IS VLBI?