Diagnosing Timing Error in WMAP Data
  The Doppler dipole signal dominates the cosmic microwave background (CMB)
anisotropy maps obtained by the Wilkinson Microwave Anisotropy Probe (WMAP)
mission, and plays a key role throughout the data processing. Previously, we
discovered a timing asynchronism of -25.6ms between the timestamps of the
spacecraft attitude and radiometer output in the original raw WMAP time-ordered
data (TOD), which, if not corrected in following data processing, would
generate an artificial quadrupole component (l=2) in recovered CMB maps (Liu,
Xiong & Li 2010). Recently, Roukema (2010b) proves that there does exist a
timing-offset-induced error corresponding to about -25.6ms in the WMAP
calibrated TOD by studying the fluctuation variance per pixel in the
temperature map recovered from the TOD as a function of assumed timing-offset.
Here, we find evidence directly in the WMAP TOD for such an uncorrected timing
error, possibly occurred in calculating the Doppler dipole signal during the
WMAP team's TOD data processing. The amplitude is highly significant and is
consistent with previous work. We also show that the uncorrected timing-offset
can lead the WMAP CMB quadrupole to be substantially overestimated.
