Wilkinson Microwave Anisotropy Probe

WMAP data processing takes into account the small transmission imbalance between the A side and the B side of the instrument. The imbalance has been measured for each radiometer using WMAP flight data, with an uncertainty of 20%. This uncertainty could lead to significant artifacts in the polarization skymaps. Spatial patterns in the Stokes Q and U maps that correspond to this uncertainty have been determined by comparing results of data simulations in which the transmission imbalance factors have been varied by ±20% from the simulation input values. We provide these Q,U templates as HEALPix Nside=16 (Res 4) maps in mK for each DA. Section 3.5.1 of Jarosik et al. (2007) describes how these templates can be projected out of the inverse covariance matrices so that transmission imbalance uncertainty will not affect subsequent analyses. The calculation is done using

(eq (27) of Jarosik et al., 2007)

where Σ^-1 is the 6144x6144 QU inverse covariance matrix for a given DA in mK^-2 and v is the 6144 element QU transmission imbalance template for the DA in mK. Note that this small correction has not been applied to the inverse covariance matrices delivered in the 5-year data release.

Additional Information

• WMAP Five Year Explanatory Supplement

• Jarosik, N., et.al., 2007, ApJS, 170, 263

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