  Synthesis imaging in radio astronomy is affected by instrumental and
atmospheric effects which introduce direction-dependent (DD) gains.The antenna
power pattern varies both as a function of time and frequency. The broad band
time varying nature of the antenna power pattern when not corrected leads to
gross errors in full Stokes imaging and flux estimation. In this poster we
explore the errors that arise in image deconvolution while not accounting for
the time and frequency dependence of the antenna power pattern. Simulations
were conducted with the wide-band full Stokes power pattern of the Karl G.
Jansky Very Large Array (VLA) antennas to demonstrate the level of errors
arising from direction-dependent gains and their non-neglegible impact on
upcoming sky surveys such as the VLASS. DD corrections through hybrid
projection algorithms are computationally expensive to perform. A highly
parallel implementation through high performance computing architectures is the
only feasible way of applying these corrections to the large data sizes of
these upcoming surveys.
