Yuntao Wu, Amir Leshem and Stefan J. Wijnholds, "A
Computationally Efficient Calibration Algorithm for the LOFAR Radio
Astronomical Array", IEEE International Conference on Acoustics,
Speech and Signal Processing, Florence (Italy), 4-9 May 2014
abstract:
In this paper, the problem of self-calibratio for large astronomical
arrays such as the Dutch Low Frequency Array (LOFAR) is considered. We
assume direction dependent gain and phase errors which need to be
estimated and calibrated out. Combining the subspace fitting and least
squares approaches, the signal subspace of the received single
short-term interval (STI) sample data of the LOFAR is used to build a
cost function whose minimizer is a statistically efficient estimator
of the unknown parameters - the gains and phases of the
telescopes. Subsequently, an iterative algorithm for finding the
minimum of the cost function is presented and the unknown calibration
parameters of both the core stations and the external subarray are
separated. As a result, the computational complexity of the proposed
method is significantly reduced compared to the existing methods based
on a direct covariance fitting. Finally, the performance of the
proposed method is compared with the conventional peeling method in
computer simulation. An example for calibrating the core of the LOFAR
array on Cyg A is also provided.
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