  Cosmology and other scientific results from the WMAP mission require an
accurate knowledge of the beam patterns in flight. While the degree of beam
knowledge for the WMAP one-year and three-year results was unprecedented for a
CMB experiment, we have significantly improved the beam determination as part
of the five-year data release. Physical optics fits are done on both the A and
the B sides for the first time. The cutoff scale of the fitted distortions on
the primary mirror is reduced by a factor of ~2 from previous analyses. These
changes enable an improvement in the hybridization of Jupiter data with beam
models, which is optimized with respect to error in the main beam solid angle.
An increase in main-beam solid angle of ~1% is found for the V2 and W1-W4
differencing assemblies. Although the five-year results are statistically
consistent with previous ones, the errors in the five-year beam transfer
functions are reduced by a factor of ~2 as compared to the three-year analysis.
We present radiometry of the planet Jupiter as a test of the beam consistency
and as a calibration standard; for an individual differencing assembly, errors
in the measured disk temperature are ~0.5%.
