PRF Estimate allows the user to make custom PRF files from their own data. In most cases, this pipeline is not necessary for Spitzer data, because the standard PRF files will be sufficient.
PRF Estimate was not designed for use with undersampled data, for example Spitzer IRAC Channels 1 and 2 data, and should not be used for such data.
7.1 Overview
The script prf_estimate.pl performs PRF estimation using either a single mosaic frame or a stack of input BCD images. The coordinates of the point sources in the input images to be used to derive a PRF are given in an input table. Optionally, background subtraction can be performed on the input images. A set of postage stamp images is cut out from each input image centered on each input point source position. The precise flux and point source positions can be optionally estimated by fitting a Gaussian to the postage stamp images. There is an option of rejecting and replacing outlier pixels and outright rejecting bad images. The postage stamp images are resampled and shifted using bicubic interpolation and combined into one final PRF image. The software has an option of deriving a set of PRFs mapped into the detector array.
7.2 Basic Input Requirements
In order to carry out PRF generation, MOPEX will expect some or all of the following files as input. See the sections on Input for more information on the format of these files.
· Either a text file containing a list of input data images from which the PRF is to be measured (e.g. Spitzer BCD frames), OR
· A single input image from which the PRF is to be measured;
· A text file containing a list of point sources to be used by PRF Estimate to create the PRF.
7.3 Running PRF Estimate
To load a PRF Estimate either start from a MOPEX template namelist (e.g. File > New PRF Estimate Pipeline), load an existing PRF Estimate namelist file (File > Read Name List) or load an empty flow and insert a PRF Estimate pipeline from there (File > New Empty MOPEX Pipeline, then go to e.g. Insert PRF Estimate at the top of the flow window and choose Empty Pipeline). If you choose the last option, MOPEX will load an empty PRF Estimate flow to which you can add and subtract modules, and modify the input parameters.
