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Last modified: 4 March 2024


PSF Issues and Caveats


With the combination of ChaRT and MARX, users may now easily perform detailed simulations of the Chandra PSF. Both of these pieces of software have limitations of which users should be aware; those limitations are described here.

The Chandra Instruments and Calibration page contains the most recent updates about the quality of the mirror (HRMA) calibrations.

As part of efforts to push the spatial resolution of Chandra to the sub-ACIS-pixel regime, we have identified a feature in the Chandra/HRC point spread function within the central arcsecond which may affect high fidelity deconvolutions. There is evidence that the feature is also present in Chandra/ACIS data. The problem does not affect images on scales larger than one arcsecond. Complete details are in the Probing higher resolution: an asymmetry in the Chandra PSF caveat.


The raytraces performed by SAOTrace are designed to precisely model the optics and their support structures, and are based upon mirror metrology, as-built and as-designed drawings of the support structure, and pre-flight tests of the HRMA. The raytraces are deterministic, rather than statistical, in that they follow individual photons through the optical system (see the Chandra optics overview for a description).

The model is calibrated by comparing it to actual observations. Such calibration is ongoing; see HRMA calibration pages and Chandra Calibration Workshop proceedings for current analyses.

The HRMA User's Guide contains a more detailed discussion of HRMA PSF characteristics, including some SAOTrace issues.