A&A Supplement Ser., Vol. 124, July 1997, 183-188
Received July 29; accepted September 25, 1996
H. LisztNational Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, U.S.A.
The usual shift and subtract algorithm 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&A 76, 92) which is commonly used to map objects bigger than a telescope's beam throw.
keywords: techniques -- image processing -- methods: observational -- methods: data analysis