The IPC deconvolution current step uses an IPC reference file.
CRDS Selection Criteria¶
IPC reference files are selected on the basis of INSTRUME and DETECTOR values for the input science data set.
IPC Reference File Format¶
IPC reference files are FITS files with one IMAGE extension, with EXTNAME value of ‘SCI’. The FITS primary data array is assumed to be empty. The SCI extension contains a floating-point data array.
Two formats are currently supported for the IPC kernel, a small 2-D array or a 4-D array. If the kernel is 2-D, its dimensions should be odd, perhaps 3 x 3 or 5 x 5 pixels. The value at the center pixel will be larger than 1 (e.g. 1.02533), and the sum of all pixel values will be equal to 1.
A 4-D kernel may be used to allow the IPC correction to vary from point to point across the image. In this case, the axes that are most rapidly varying (the last two, in Python notation; the first two, in IRAF notation) have dimensions equal to those of a full-frame image. At each point in that image, there will be a small, 2-D kernel as described in the previous paragraph.