XIMAGE is a multi-mission X-ray image display and analysis program. It is designed to be instrument independent and to support the analysis of data from any X-ray imaging detector provided that the proper calibration files are available. Currently XIMAGE supports the detailed analysis of EXOSAT CMA, Einstein HRI and IPC, ROSAT PSPC and HRI, ASCA GIS and SIS, BeppoSAX MECS and LECS data. It also supports some basic analysis of optical, infrared and radio images. The following functions are provided:
The display and graphic capabilities of XIMAGE are based on the PGPLOT graphic package, which supports most terminals and workstations. The programs, saoimage and POWplot can also be spawned to display images and select regions.
While XIMAGE is a multimission package, it must first "know" about the calibration information associated with a mission in order to be able to make a detailed image analysis. Some XIMAGE functions are mission independent (e.g. display), but others are not (e.g. source detect). XIMAGE will read in images from an unknown mission, but the user should beware trying to make a detailed analysis. A warning will be issued if the mission is unknown. A list of known missions can be obtained by giving the command chmdb/list. Adding new missions usually requires either adding new files and/or adding new calls and relinking XIMAGE.
XIMAGE is based on original routines developed as part of the EXOSAT interactive image analysis system. These routines have been restructured and assembled as part of a multimission command driven interactive software package running as part of the XANADU infrastructure.
Performing image analysis requires the following calibration items to be known:
The first two are critical for XIMAGE to produce any useful results. The vignetting can be provided as an image map, or as a function. In the latter case the XIMAGE code must be relinked. The PSF can be derived from within XIMAGE, and read in as a file. The exposure map is optional, and if it is not available then it is assumed the image exposure is uniform. This is usually acceptable for detectors without any obstructing structures (e.g. the EXOSAT CMA), but will lead to errors if there are window supports (e.g. the ROSAT PSPC). The background map is also optional, and is only necessary in the case where there is significant variation in the particle background across the detector.
The vignetting function and the PSF can be energy dependent (e.g. the ROSAT PSPC), and care must be taken to ensure that they match the energy band of the image.
XIMAGE is written by astronomers, for astronomers. This has the advantage that its requirements are driven by real needs, and so it tends to do things in the most natural way and usually very efficiently. While every effort has been made to get things right, the user should always make an attempt to "understand" what ximage is doing to produce the given results.
The XIMAGE package can be obtained for several platforms including Dec-OSF, SunOS, and Linux. Compressed tar files can be obtained at http://heasarc.gsfc.nasa.gov/lheasoft/ or write to xanprob@legacy.gsfc.nasa.gov.
Any problems in obtaining or installing XIMAGE should be reported to xanprob@legacy.gsfc.nasa.gov. Any questions or problems with XIMAGE or requests to add additional instruments should be directed to angelini@lheamail.gsfc.nasa.gov or micah@lheamail.gsfc.nasa.gov.