Recovering line profiles from frequency-switched spectra

National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, U.S.A.

Received: 29 July 1996
Accepted: 25 September 1996

Abstract

The usual shift and subtractalgorithm for recovering line profiles from frequency-switched data succeeds only when the switching interval exceeds the extent of the signal-bearing region. Nonetheless, noiseless spectra can in principle be reconstructed without error for any frequency-switching interval of at least one channel. This work presents a simple recursive algorithm which recovers line profiles from spectra which might otherwise appear hopelessly damaged, with only a slight cost in signal/noise. It is functionally equivalent to the dual-beam restoration algorithm of Emerson et al. (1979, A&A76, 92) which is commonly used to map objects bigger than a telescope's beam throw.