  The next-generation space VLBI mission, VSOP-2, is expected to provide
unprecedented spatial resolutions at 8.4, 22, and 43GHz. In this report, phase
referencing with VSOP-2 is examined in detail based on a simulation tool called
ARIS. The criterion for successful phase referencing was to keep the phase
errors below one radian. Simulations with ARIS reveal that phase referencing
achieves good performance at 8.4GHz, even under poor tropospheric conditions.
At 22 and 43GHz, it is recommended to conduct phase referencing observations
under good or typical tropospheric conditions. The satellite is required to
have an attitude-switching capability with a one-minute or shorter cycle, and
an orbit determination accuracy higher than about 10cm at apogee; the phase
referencing calibrators are required to have a signal-to-noise ratio larger
than four for a single scan. The probability to find a suitable phase
referencing calibrator was estimated by using VLBI surveys. From the viewpoint
of calibrator availability, VSOP-2 phase referencing at 8.4GHz is promising.
However, the change of finding suitable calibrators at 22 and 43GHz is
significantly reduced; it is important to conduct specific investigations for
each target at those frequencies.
