First year Wilkinson Microwave Anisotropy Probe (WMAP) observations: Beam profiles and window functions
Feb, 200312 pages
Published in:
- Astrophys.J.Suppl. 148 (2003) 39
e-Print:
- astro-ph/0302214 [astro-ph]
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Abstract: (arXiv)
Knowledge of the beam profiles is of critical importance for interpreting data from cosmic microwave background experiments. In this paper, we present the characterization of the in-flight optical response of the WMAP satellite. The main beam intensities have been mapped to < -30 dB of their peak values by observing Jupiter with the satellite in the same observing mode as for CMB observations. The beam patterns closely follow the pre-launch expectations. The full width at half maximum is a function of frequency and ranges from 0.82 degrees at 23 GHz to 0.21 degrees at 94 GHz: however, the beams are not Gaussian. We present: (a) the beam patterns for all ten differential radiometers and show that the patterns are substantially independent of polarization in all but the 23 GHz channel: (b) the effective symmetrized beam patterns that result from WMAP's compound spin observing pattern: (c) the effective window functions for all radiometers and the formalism for propagating the window function uncertainty: and (d) the conversion factor from point source flux to antenna temperature. A summary of the systematic uncertainties, which currently dominate our knowledge of the beams, is also presented. The constancy of Jupiter's temperature within a frequency band is an essential check of the optical system. The tests enable us to report a calibration of Jupiter to 1-3% accuracy relative to the CMB dipole.References(9)
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