  We describe the motivation and features of a multiwavelength spectroscopic
campaign on broad absorption line (BAL) QSO PG~0946+301. The main goal of this
project is to determine the ionization equilibrium and abundances (IEA) in BAL
outflows. Previous studies of IEA in BALQSOs were based on the assumption that
the BALs are not saturated so that the column densities inferred from the
apparent optical depths are realistic. This critical assumption is at odds with
several recent observations and with analysis of existing data which indicate
that the absorption troughs are heavily saturated even when they are not black.
In addition, X-ray observations, which are important for constraining the
ionizing continuum, were not available for those objects that had UV spectral
data. Quantifying the level of saturation in the BALs necessitates UV
spectroscopy with much higher S/N and broader spectral coverage than currently
exist. After taking into account the capabilities of available observatories,
our best hope for a substantial improvement in understanding the IEA in BALQSOs
is to concentrate considerable observational resources on the most promising
object. Our studies of available HST and ground-based spectra show that
PG~0946+301 is by far the best candidate for such a program. This BALQSO is at
least five times brighter, shortward of 1000 A rest frame, than any other
object, and due to its low redshift it has an especially sparse Lya forest. At
the same time PG~0946+301 is a typical BALQSO and therefore its IEA should be
representative. To this effect we are developing a multiwavelength
spectroscopic campaign (UV, FUV, X-ray and optical) on BALQSO PG 0946+301. We
discuss the goals and feasibility of each observational component: HST, FUSE,
ASCA and ground-based.
