MOPEX (MOsaicking and Point Source Extraction) is a package developed at the Spitzer Science Center for astronomical image processing. MOPEX requires input images in FITS format. As an example, if the user has basic calibrated FITS images from the Spitzer Space Telescope archive, MOPEX can be used to level the backgrounds of the input images, co-add them together to produce a mosaic with optional rejection of outliers (e.g. cosmic rays), and perform point source extraction and/or aperture photometry on the detected sources.
MOPEX can be run in two ways - either from the command line, or using the Graphical User Interface (GUI). The GUI is more user-friendly, especially for first-time users, but the command line contains some additional functionality that has not yet been implemented in the GUI. MOPEX is available for Mac, Linux and Solaris (see the MOPEX Download page for specific availability).
***NEW (November 2010)*** Appendix C gives the current best correction factors for PSF-fitted fluxes for all Spitzer instruments.
***NEW (March 2012)*** Appendix D gives some tips for Spitzer data.
1.1 Important Documentation
The following documents and webpages are recommended reading, and are referred to throughout this User’s Guide:
The Graphical User Interface (GUI) and the command-line versions of MOPEX are packaged and released together, and all updates to both versions are done through the GUI. Both versions use the same set of C++ and C programs to carry out the data reduction. Generally, users may wish to start with the GUI as it provides a more intuitive interface, nice visualization of each processing step and its output, and includes useful image display tools. Users may use the command-line version to script their data reduction, take advantage of the slightly faster processing time, or to use some of the additional functionality not yet available through the GUI.
1.3 Getting Help
Online help for MOPEX is available from the Help function in the GUI. A full list of the known bugs, along with suggested solutions or work-arounds, can be found on the MOPEX Bug List. The Spitzer Helpdesk also contains a KnowledgeBase of frequently asked questions.
If you still have questions about MOPEX then you can get help by submitting a ticket to the Spitzer Helpdesk or emailing us at help@spitzer.caltech.edu. Please help us by including the following information:
The operating system you are running (e.g. Mac OS10.6 or Linux RHEL);
Which version of MOPEX you’re using (GUI or command line) and the version number (e.g. 18.5.0 Final);
The AOR ID of your data (if Spitzer data);
Attach your namelist, unless it’s a standard MOPEX template, in which case tell us which one;
A description of the error message you saw;
If you are using the GUI, please attach the most recent log file, found in the directory ~/.spot/
As much information as possible about the problem, including any processing steps you carried out since downloading the data from the archive.
Please note that our system does not autoreply, so if you receive a reply from us within a few minutes then please check it for further information.
1.4 Why MOPEX?
MOPEX provides a general-purpose tool to generate mosaics of FITS images and to perform point source extraction. While other tools are available for these tasks, MOPEX addresses several complications specific to Spitzer data:
Geometric Distortion: Spitzer images have significant geometric distortion, described in the FITS header using the World Coordinate System (WCS). Mosaicking and photometry must accurately interpret this information, which is not yet standard in all packages.
Fast Projection: Large Spitzer mosaics include many images, so a fast method is required when performing the projection. MOPEX’s fast direct plane-to-plane projection is described in Makovoz, D. 2004, PASP, 116, 971-974.
Outlier Rejection: Like many datasets, Spitzer data suffer from cosmic rays and other artifacts. The best algorithm for rejecting these outliers depends upon the observing mode, e.g. simple temporal outlier rejection works well with highly redundant sky coverage, but it can fail without it. MOPEX has single-frame spatial, temporal and two spatial-plus-temporal outlier rejection methods that can be adjusted for different observing modes.
Profile Fitting: Spitzer pixels are relatively big relative to point sources, so MOPEX fits with Point Response Functions (PRFs), which take into account intra-pixel sensitivities. For multi-frame photometry, MOPEX does detection on a mosaic image, but point-source fitting on the original stack of images.
In addition to solving these specific problems, MOPEX provides some useful tools for mosaicking and source extraction. Mosaicking options include background matching, drizzle interpolation, exposure time weighting, and error propagation. Photometry options include detection using image segmentation, use of a previous list of detected positions for photometry, aperture photometry, and residual image generation.
1.5 How To Use This Manual
This manual is split into the following parts:
Introductory material for MOPEX in general, including installation instructions and a quick start guide;
An overview of the software and its capabilities;
Input files and requirements for MOPEX;
An in-depth description of all the pipelines and modules available in MOPEX;
Basic Concepts in MOPEX, with in-depth discussions of the algorithms implemented;
Running MOPEX on the command line;
Appendices, with useful tables and supplementary material.
The bulk of this document describes how to run MOPEX from the GUI, but Chapter 9 provides details of how to run MOPEX from the command line.
For the purposes of this manual, we will call the directory containing your data <data_dir>, the directory in which you have installed MOPEX <mopex_dir>, and the directory from which you are planning to run MOPEX <working_dir> (which may be the same as <data_dir> or <mopex_dir> but doesn’t have to be).
