Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations:
  Planets and Celestial Calibration Sources
  (Abridged) We present WMAP seven-year observations of bright sources which
are often used as calibrators at microwave frequencies. Ten objects are studied
in five frequency bands (23 - 94 GHz): the outer planets (Mars, Jupiter,
Saturn, Uranus and Neptune) and five fixed celestial sources (Cas A, Tau A, Cyg
A, 3C274 and 3C58). The seven-year analysis of Jupiter provides temperatures
which are within 1-sigma of the previously published WMAP five-year values,
with slightly tighter constraints on variability with orbital phase, and limits
(but no detections) on linear polarization. Scaling factors are provided which,
when multiplied by the Wright Mars thermal model predictions at 350 micron,
reproduce WMAP seasonally averaged observations of Mars within ~2%. An
empirical model is described which fits brightness variations of Saturn due to
geometrical effects and can be used to predict the WMAP observations to within
3%. Seven-year mean temperatures for Uranus and Neptune are also tabulated.
Uncertainties in Uranus temperatures are 3%-4% in the 41, 61 and 94 GHz bands;
the smallest uncertainty for Neptune is ~8% for the 94 GHz band. Intriguingly,
the spectrum of Uranus appears to show a dip at ~30 GHz of unidentified origin,
although the feature is not of high statistical significance. Flux densities
for the five selected fixed celestial sources are derived from the seven-year
WMAP sky maps, and are tabulated for Stokes I, Q and U, along with polarization
fraction and position angle. Fractional uncertainties for the Stokes I fluxes
are typically 1% to 3%. Source variability over the seven-year baseline is also
estimated. Significant secular decrease is seen for Cas A and Tau A: our
results are consistent with a frequency independent decrease of about 0.53% per
year for Cas A and 0.22% per year for Tau A.
