  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.
