MOPEX: Pointing Refinement
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Purpose and Description
Pointing refinement is now done for IRAC data as part of the Spitzer pipeline. Do not use this script with IRAC data - it should only be used with MIPS-24 or IRS Peak-Up Imaging data.Pointing_refine.pl is distributed as part of MOPEX. It performs pointing refinement for FITS images. This is achieved by minimizing the discrepancy between the
positions of point sources matched in each pair of the images. Global
minimization of the cumulative discrepancy with respect to small changes
in the pointing of the input images is implemented using a generic linear
sparse matrix solver. The software has two modes of operation:
"relative" and "absolute." In the relative refinement mode, the images are
made self-consistent. In the absolute mode, a list of real point sources is
used as one of input lists. This results in fixing the absolute pointing
of the input images.
The processing includes the following steps. First, point source
extraction is performed by running the single-frame point source
extraction package. For each input image, a list of point sources is
created. The list is trimmed using the signal-to-noise ratio (SNR)
threshold. This is done by running the select module. In the
relative mode, the point source lists then are fed into the
pointingrefine module, which produces an output table with the
refined pointing and the uncertainties for each image. The refined
pointing is also written in the header of each input image using new
keywords. In the absolute refine mode, a list of sources with absolute
pointing is needed. Module fiducial_image_frame computes an an
area of the sky that includes in some optimal fashion all of the input
images. A query to the 2MASS catalog in the IRSA database is then made
and a list of 2MASS point sources found within that area is created.
There is an option of running the package with simulated data. In this
case, in the absolute refine mode the list of sources with absolute
pointing is replaced with the truth list of point sources used to simulate
the images.
Downloading and Installing the Software
Pointing_refine.pl is distributed as part of MOPEX.
Running Pointing Refinement
A brief introduction on how to run Pointing Refinement.Pipeline (S10.5 and S11) Namelists
See Online Pipeline History Log for a description of the S10.5 and S11 pipelines.- For IRAC Channel 1: pointing_refine_I1.nl
- For IRAC Channel 2: pointing_refine_I2.nl
- For IRAC Channel 3: pointing_refine_I3.nl
- For IRAC Channel 4: pointing_refine_I4.nl
- For MIPS 24 microns: pointing_refine_M1.nl
WARNING: The input variables require a space preceeding and following the equals sign, i.e. "variable = value". An entry like "variable=value" will not be read and the hard-coded default will be used so you will not notice that your input value is not being used.
Description of Modules
| Pointing Refinement Modules |
User's Guides
Supporting Documentation
- A Robust Algorithm for the Pointing Refinement and Registration of Astronomical Images, by Masci et al., 2004, PASP, 116, 842
- Pointing Refinement (technical description)
- Also see the Main Documentation Page for additional documents.
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