Contribution of X/Ka VLBI to multi-wavelength celestial frame studies

Abstract

This paper is an update of Sotuela et al. (2011) which improves their simulated Gaia frame tie precision by ~10% by adding three additional VLBI observing sessions. Astrometry at X/Ka-band (8.4/32 GHz) using NASAs Deep Space Network has detected 466 quassars with accuracies of 200-300 μas. A program is underway to reduce errors by a factor of 2-3. From our sample, 245 sources have optical magnitudes V < 20 and should also be detectable by Gaia. A covariance study using existing X/Ka data and simulated Gaia uncertainties for the 345 objects yields a frame tie precision of 10-15 μas (1-σ)/ The characterization of wavelength dependent systematic from extended source morphology and core shift should benefit greatly from adding X/Ka-band measurements to S/X-band (2.3/8.4 GHz) measurements thus helping to constrain astrophysical models of the wavelength dependence of positions.