VLBA Scientific Memorandum n. 32 - Multi-frequency Astrometry with VSOP-2: An application of Source/Frequency Phase Referencing techniques

This document describes the advantages of applying "Source/Frequency Phase Referencing" (SFPR) techniques to the analysis of VLBI observations with VSOP-2, for high precision astrometric measurements and/or increased sensitivity. The SFPR calibration technique basics and a demonstration of the method applied to highest frequency VLBA observations are described in detail in VLBA Scientific Memo n. 31. Here we outline its importance in the context of space VLBI astrometry with VSOP-2, where errors in the satellite orbit determination and rapid tropospheric phase fluctuations set extreme challenges for the successful application of conventional phase referencing techniques, specially at the higher frequencies. SFPR is ideally suited for full calibration of those - regardless of the orbit determination accuracy - and, in general, of any non-dispersive terms. The requirements for application of SFPR techniques are fully compatible with current technical specifications of VSOP-2. Hence we foresee that SFPR will play an important role in helping expanding the scientific outcome of the space VLBI mission.