  We report a comprehensive analysis of the global spectrophotometric
properties of Ceres using Dawn Framing Camera images collected from April to
June 2015 during the RC3 and Survey mission phases. The single-scattering
albedo of Ceres at 555 nm is 0.14$\pm$0.04, the geometric albedo is
0.096$\pm$0.006, and the Bond albedo is 0.037$\pm$0.002. The asymmetry factors
calculated from the best-fit two-term Henyey-Greenstein (HG) single-particle
phase function (SPPF) show a wavelength dependence, suggesting that the phase
reddening of Ceres is dominated by single-particle scattering rather than
multiple scattering or small-scale surface roughness. The Hapke roughness
parameter of Ceres is derived to be 20$^\circ\pm$6$^\circ$ with no wavelength
dependence. The phase function of Ceres shows appreciably strong scattering
around 90$^\circ$ phase angle that cannot be fitted with a single-term HG SPPF,
suggesting possible stronger forward scattering than other asteroids previously
analyzed with spacecraft data. We speculate that such a scattering
characteristic of Ceres might be related to its unique surface composition. We
grouped the reflectance data into a 1$^\circ$ latitude-longitude grid and
fitted each grid independently to study the spatial variations of photometric
properties. The albedo and color maps are consistent with previous studies. The
SPPF over the surface of Ceres shows stronger backscattering associated with
lower albedo and vice versa, consistent with the general trend among asteroids.
The Hapke roughness parameter does not vary much across the surface of Ceres,
except for the ancient Vendimia Planitia region that has a slightly higher
roughness. Based on the wavelength dependence of the SPPF of Ceres, we
hypothesize that its regolith grains either contain a considerable fraction of
$\lessapprox\mu$m-sized particles, or are strongly affected by internal
scatterers of this size.
