EVLA Memo 146 RFI Mitigation in AIPS. The New Task UVRFI

Recently Ramana Athrea published a new algorithm ([1]) based on the difference at fringe rates of a source in the sky and ground-based RFI. His algorithm works only for ground-based and constantamplitude RFI during a solution interval. We modified his algorithm to include a possible change of the RFI’s amplitude during the solution interval and developed another algorithm based on Högbom CLEANing of the Fourier transform of the time series of the SOURCE+RFI visibilities. These algorithms allow us to mitigate RFI originating from more than one source moving with different nonzero speeds relatively the array (e.g. ground-based and satellite-based RFI). The new algorithms are implemented in AIPS ([2]) in the task UVRFI. The result of testing this task is demonstrated using the EVLA data at L and 4 band. It is also shown that self-averaging of RFI can reduce its impact on imaging even if the solution interval in the correlator is too small to allow self-averaging before imaging.