The Correlation Calibration of PAPER-64 data
  Observation of redshifted 21-cm signal from the Epoch of Reionization (EoR)
is challenging due to contamination from the bright foreground sources that
exceed the signal by several orders of magnitude. The removal of this very high
foreground relies on accurate calibration to keep the intrinsic property of the
foreground with frequency. Commonly employed calibration techniques for these
experiments are the sky model-based and the redundant baseline-based
calibration approaches. However, the sky model-based and redundant
baseline-based calibration methods could suffer from sky-modeling error and
array redundancy imperfection issues, respectively. In this work, we introduce
the hybrid correlation calibration ("CorrCal") scheme, which aims to bridge the
gap between redundant and sky-based calibration by relaxing redundancy of the
array and including sky information into the calibration formalisms. We
demonstrate the slight improvement of power spectra, about $-6\%$ deviation at
the bin right on the horizon limit of the foreground wedge-like structure,
relative to the power spectra before the implementation of "CorrCal" to the
data from the Precision Array for Probing the Epoch of Reionization (PAPER)
experiment, which was otherwise calibrated using redundant baseline
calibration. This small improvement of the foreground power spectra around the
wedge limit could be suggestive of reduced spectral structure in the data after
"CorrCal" calibration, which lays the foundation for future improvement of the
calibration algorithm and implementation method.
