  The launch of the Nuclear Spectroscopic Telescope Array (NuSTAR) heralded a
new era of sensitive high energy X-ray spectroscopy for X-ray binaries (XRBs).
In this paper we show how multiple physical parameters can be measured from the
accretion disk spectrum when the high-energy side of the disk spectrum can be
measured precisely using NuSTAR. This immediately makes two exciting
developments possible. If the mass and distance of the source are known, the
continuum fitting method can be used to calculate the spin and inner disk
inclination independently of the iron line fitting method. If the mass and
distance are unknown, the two methods can be combined to constrain these values
to a narrow region of parameter space. In this paper we perform extensive
simulations to establish the reliability of these techniques. We find that with
high quality spectra, spin and inclination can indeed be simultaneously
measured using the disk spectrum. These measurements are much more precise at
higher spin values, where the relativistic effects are stronger. The inclusion
of a soft X-ray snapshot observation alongside the NuSTAR data significantly
improves the reliability, particularly for lower temperature disks, as it gives
a greatly improved measurement of the disk peak. High signal to noise data are
not necessary for this, as measuring the peak temperature is relatively easy.
We discuss the impact of systematic effects on this technique, and the
implications of our results such as robust measurements of accretion disk warps
and XRB mass surveys.
