Stripping of cosmic spike spectral artifacts using a new upper-bound spectrum algorithm

A new upper-bound spectrum (UBS) method for removal of cosmic spike artifac ts from spectra or images collected using a charge-coupled device (CCD) det ector is proposed. This algorithm, which is shown to outperform previous me thods, relies on an upper-bound spectrum, derived from scaled copies of con secutively collected spectra, which serves as a threshold for the detection of suspected cosmic spikes. Detected spikes are removed by replacement wit h the corresponding points in other spectra. Thus, unlike other commonly us ed methods, the UBS algorithm requires no smoothing or noise filtering and more reliably removes cosmic spikes of all magnitudes while introducing far less (if any) spectral distortion. The UBS method is tested using both syn thetic and experimental (gypsum and gypsum/hematite mixture) spectra contai ning variable background (fluorescence), noise, and cosmic spike interferen ce. The UBS method may in rare instances mistakenly identify spectral noise or photo-induced changes in band intensity (or shape) as cosmic spikes. Ho wever, as demonstrated through the use of both synthetic and experimental e xamples, such misidentifications produce little or no spectral distortion o r artifacts in the resulting cosmic-spike-free output spectra.