  With Hubble Space Telescope Fine Guidance Sensor astrometry and published and
previously unpublished radial velocity measures we explore the exoplanetary
system mu Arae. Our modeling of the radial velocities results in improved
orbital elements for the four previously known components. Our astrometry
contains no evidence for any known companion, but provides upper limits for
three companion masses. A final summary of all past Fine Guidance Sensor
exoplanet astrometry results uncover a bias towards small inclinations (more
face-on than edge-on). This bias remains unexplained by either small number
statistics, modeling technique, Fine Guidance Sensor mechanical issues, or
orbit modeling of noise-dominated data. A numerical analysis using our refined
orbital elements suggests that planet d renders the mu Arae system dynamically
unstable on a timescale of 10^5 years, in broad agreement with previous work.
