Improvements to the image processing of HST NICMOS observations with multiple readouts

Author(s): Fadeyev, Vitaliy; Aldering, Gregory; Perlmutter, Saul | Abstract: We report on improvements made to the standard NICMOS processing pipeline. The calculation of the uncertainties on the signal accumulation rate has been modified to include the statistical correlations between the consecutive readouts. In order to correcta problem with the existing cosmic ray rejection algorithm, we have developed and implemented a joint fit procedure, where the accumulating signal is fit as linear functions of time with the same rate both before and after the cosmic ray (CR) impact. We also accounted for inter-pixel correlations in the CR-affected region. The new processing is most relevant for deep observations of faint targets, and for PSF fitting, for which unbiased measurements of accurate error estimates are important. We show examples of these improvements for deep NIC2 images of high-red shift supernova from the Supernova Cosmology Project.